Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system

Universidade do Minho Escola de Engenharia Lombe Mutale Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system september 2021 UMinho | 2021 Lombe Mutale Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Co-funded by the Erasmus+ Programme of the European Union The European Master in Building Information Modelling is a joint initiative of: September 2021 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Universidade do Minho Escola de Engenharia Lombe Mutale Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Master Dissertation European Master in Building Information Modelling Work conducted under supervision of: Miguel Azenha Bruno Figueiredo Carlos Gomes (Tutor in Company) September, 2021 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ ii AUTHORSHIP RIGHTS AND CONDITIONS OF USE OF THE WORK BY THIRD PARTIES This is an academic work that can be used by third parties, as long as internationally accepted rules and good practices are respected, particularly in what concerts to author rights and related matters. Therefore, the present work may be used according to the terms of the license shown below. If the user needs permission to make use if this work in conditions that are not part of the licensing mentioned below, he/she should contact the author through the RepositóriUM platform of the University of Minho. License granted to the users of this work Attribution CC BY https://creativecommons.org/licenses/by/4.0/ Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ iii ACKNOWLEDGEMENTS I would like to express my deepest gratitude to my supervisors Professor Miguel Azenha, Professor Bruno Figueiredo and Carlos Gomes who provided invaluable feedback and support throughout the dissertation period. Many thanks to the Erasmus Mundus Programme of the European Union for the provision of a scholarship that funded my studies and made my life much easier. Thank you to Professor Nuno Mendes who provided DIANA FEA advice and support; Renato Correia who was kind enough to allow the use of his C# script and tirelessly answered all my questions; Samuel Ribeiro at the University of Minho Design Institute and Benedetta Boso who assisted with the creation of the 3D printed prototype and photo montage and patiently made sure we got it right. Further thanks to the BIM A+ staff and my fellow students in the BIM A+ 2020/2021 cohort for a memorable year, that was more than I could have ever imagined and will always cherish. Last by not least, special thanks to my family and friends for their continuous support and encouragement. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ iv STATEMENT OF INTEGRITY I hereby declare having conducted this academic work with integrity. I confirm that I have not used plagiarism or any form of undue use of information or falsification of results along the process leading to its elaboration. I further declare that I have fully acknowledged the Code of Ethical Conduct of the University of Minho. Lombe Mutale Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ v RESUMO Atualmente, a indústria da construção é a maior do mundo, sendo responsável por 8% das emissões de gases de efeito estufa, principalmente devido ao betão, que é o material mais comum usado na construção. O betão armado recorre a armaduras em aço, que estão particularmente sujeitas à corrosão quando ocorre fissuração e decorrente penetração de agentes agressivos do exterior. A corrosão generalizada do aço afeta a durabilidade de toda a estrutura, reduz sua vida útil e aumenta a necessidade de reabilitação e manutenção durante seu ciclo de vida. Uma alternativa interessante, em prol da otimização, durabilidade e minimização do desperdício de material, conceber estruturas de betão unicamente sujeitas a esforços de compressão e, evitando portanto a necessidade de utilização de armaduras. Isso pode ser alcançado através da aplicação de métodos de otimização da forma da estrutura. É também sabido que os sistemas pré-fabricados permitem otimização e aumento de produtividade na indústria da construção, por comparação com os métodos tradicionais de construção in-situ. Além disso, a digitalização por meio de BIM e processos de projeto computacional podem automatizar e auxiliar na redução de custos e garantia de qualidade. Esta dissertação propõe o uso de betão de baixa resistência para criar estruturas pré-fabricadas de betão, sujeitas unicamente a esforços de compressão. Cada parte discreta da estrutura (módulos de cerca de um metro quadrado de área) é feita por meio de moldes flexíveis que se adaptam a uma ampla gama de geometrias. Os componentes estruturais são conectados por cabos de pré-esforço (em material não metálico, evitando efeitos de corrosão) que são instalados no local, criando assim um novo sistema de construção. Em suma, o sistema visa satisfazer os seguintes requisitos: i) ser autoportante durante a construção, ou precisando apenas de escoramento limitado; ii) comportamento estrutural otimizado (somente compressão - sem momentos de flexão), iii) alta durabilidade e longa vida útil (sem armaduras metálicas). No âmbito da dissertação são utilizados algoritmos computacionais para criar uma forma estrutural de casca somente de compressão por meio de métodos conhecidos por ‘form finding’ no Rhinoceros / Grasshopper 3D. Uma vez obtida a forma estrutural geral, foi-lhe atribuída espessura e compartimentação (tecelagem), definindo assim seus elementos discretos. A sequência de construção dos elementos préfabricados foi implementada automaticamente com algoritmos de automação celular. Em seguida, foi criada uma ferramenta customizada que permite interoperabilidade automática do modelo criado para o software de análise estrutural DIANA e automatizou a análise em fases que incorporou a sequência construtiva. Posteriormente, foi usada a análise pelo método dos elementos finitos para avaliar o comportamento estrutural. Por fim, é proposto um fluxo de trabalho colaborativo entre engenheiros e arquitetos, rumo à definição conjunta de formas otimizadas com o procedimento desenvolvido nesta dissertação. Por meio de um estudo de caso para testar a estrutura, os resultados mostram que o fluxo de trabalho proposto é viável, podendo ser aplicável a outras geometrias mais complexas. Refira-se que embora existam algumas tensões de tração presentes durante a construção em fases, elas podem ser quase eliminadas com o uso de suportes de construção provisórios (meros escoramentos tipicamente usados na construção) com pouco impacto nos custos e tempo de construção. Palavras-chave: método do elementos finitos, otimização de forma, interoperabilidade, pré-fabricação, modelação paramétrica) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ vi ABSTRACT Currently, the construction industry is the largest industry in the world and contributes 8% per year to greenhouse gas emissions mostly due to concrete which is the most common material used for construction. Reinforced concrete needs steel reinforcement which is prone to rust when the concrete cracks and deleterious materials reach the steel. Widespread steel corrosion affects the durability of the entire structure, reduces its service life, and increases the need for rehabilitation and maintenance during its lifecycle. An interesting alternative, for the sake of optimisation, durability, and material waste minimisation, would be to make concrete structures solely endure compression forces and hence avoid the need to use steel reinforcement. This can be achieved through applying form-finding methods to achieve optimised structural shapes. Precast systems can further optimise and increase the industry’s productivity more than the traditional on-site construction systems can. Additionally, digitalisation through BIM and computational design processes can automate and assist in cost savings and quality assurance. This dissertation proposes the use of low-strength concrete to create precast compression-only concrete structures. Each discrete part of the structure is made through flexible moulds that are adaptable to a wide range of geometries. The structural components are connected by prestressing cables (not made of steel and not prone to corrosion) which are installed in-situ thereby creating a new construction system. In short, the system aims to satisfy the following requirements i) self-supporting during construction, or only needing some propping ii) optimised structural behaviour (compression-only – no bending moments), iii) high durability and long service life (no reinforcement). Computational and parametric design were used to create a compression-only shell structural shape through the Particle Spring form-finding method in Rhinoceros/Grasshopper 3D. Once the overall structural shape was obtained, it was thickened and tessellated thereby defining its discrete elements. The construction sequence of precast elements was implemented automatically with a cellular automata algorithm. Then, a custom tool was created that linked the structural shape generated to the structural analysis software DIANA and automated the phased analysis which incorporated the construction sequencing. Thereafter, finite element analysis (FEA) was used to assess the structural behaviour. Finally, a collaborative workflow was set up such that engineers and architects can work together to create the most optimal structural shape in a BIM environment. Through a case study to evaluate the framework, results show that with the proposed workflow, any arbitrary compression-only structural shape can be defined using form-finding principles. FEA can be performed for structural analysis and a BIM model produced for construction. Although, there are some tensile stresses present during the phased construction they can be almost eliminated with the use of minimal construction supports. Keywords: (FEA, form-finding, interoperability, modular construction, parametric modelling) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ vii TABLE OF CONTENTS 1. INTRODUCTION ............................................................................................................. 15 1.1. SCOPE AND MOTIVATION .............................................................................................. 15 1.2. OBJECTIVES AND METHODOLOGY .............................................................................. 17 1.3. STRUCTURE OF DISSERTATION .................................................................................... 18 2. SUSTAINABLE DESIGN AND CONSTRUCTION OF SHELL STRUCTURES USING DIGITAL PROCESSES & TECHNOLOGIES ....................................................................... 19 2.1. INTRODUCTION ................................................................................................................. 19 2.2. THE PRINCIPLE OF PERPECTUM ................................................................................... 20 2.3. SHELL STRUCTURES ........................................................................................................ 21 2.3.1. Definition, advantages and disadvantages ..................................................................... 21 2.3.2. Form-finding methods for obtaining shell geometry ..................................................... 22 2.3.3. Structural analysis ......................................................................................................... 24 2.4. MODULAR CONSTRUCTION SYSTEMS ........................................................................ 26 2.5. DESIGN AND CONSTRUCTION OF SHELL STRUCTURES ......................................... 28 2.5.1. Computational design and parametric modelling for shell structures ........................... 28 2.5.2. Prefabricated sequential construction ............................................................................ 31 2.6. COLLABORATIVE BIM BASED WORKFLOWS ............................................................ 33 2.6.1. Digitalisation ................................................................................................................. 33 2.6.2. Computational Design, Formwork development and physical prototyping .................. 34 2.6.3. An integrated framework for multi-criteria optimization of thin concrete shells .......... 36 3. PARAMETRIC MODELLING AND COMPUTATIONAL DESIGN TOWARDS MODEL GENERATION ......................................................................................................... 39 3.1. INTRODUCTION ................................................................................................................. 39 3.2. GEOMETRICAL CONCEPT FOR VAULT SYSTEM ....................................................... 39 3.3. OVERVIEW OF PARAMETRIC MODELLING AND COMPUTATIONAL DESIGN WORKFLOW ................................................................................................................................... 40 3.4. IMPLEMENTATION OF THE COMPUTATIONAL DESIGN MODEL .......................... 41 3.4.1. Structural equilibrium by form-finding ......................................................................... 41 3.4.2. Thickening, tessellating and discretisation of the structure ........................................... 43 3.4.3. Generation of cable curves ............................................................................................ 45 3.4.4. Creating the assembly sequence using a cellular automata algorithm .......................... 47 3.4.5. Connection and interoperability with BIM platform including level of information need 52 3.5. 3D PRINTING ...................................................................................................................... 54 4. STRUCTURAL ANALYSIS PROCEDURES ................................................................. 57 4.1. INTRODUCTION ................................................................................................................. 57 4.2. STRUCTURAL CONCEPT OF THE CONSTRUCTION SYSTEM .................................. 57 4.2.1. Panel size and material .................................................................................................. 57 4.2.2. Post tensioning load ...................................................................................................... 58 4.2.3. Temporary supports during construction ...................................................................... 59 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ viii 4.3. INTEROPERABILITY TOOL FOR CONNECTION BETWEEN MODELLING PLATFORM AND STRUCTURAL ANALYSIS SOFTWARE ...................................................... 59 4.4. DIANA FEA PROPERTY ASSIGNMENT AND PHASED ANALYSIS PROCEDURES 60 4.4.1. Property assignment procedure...................................................................................... 60 4.4.2. DIANA Phased Analysis ............................................................................................... 61 4.5. DIANA EXAMPLES ............................................................................................................ 62 4.5.1. Four-block model phased analysis ................................................................................ 62 4.5.2. Python scripting for DIANA ......................................................................................... 64 4.6. SCRIPT FOR PROPERTY ASSIGNMENT AND CONSTRUCTION PHASING ............. 65 5. FRAMEWORK DEFINITION AND CASE STUDY ..................................................... 67 5.1. INTRODUCTION ................................................................................................................. 67 5.2. FRAMEWORK FOR WORKFLOW WITH ARCHITECT AND STRUCTURAL ENGINEER ....................................................................................................................................... 67 5.3. CASE STUDY OF A NEW SUSTAINABLE COMPRESSION-ONLY STRUCTURAL BLOCK CONSTRUCTION SYSTEM ............................................................................................. 72 5.3.1. Parametric modelling ..................................................................................................... 72 5.3.2. Structural description: supports, material properties and loading ................................. 76 5.3.2.1. Boundary conditions .................................................................................................. 77 5.3.2.2. Material properties ..................................................................................................... 77 5.3.2.3. Loads ......................................................................................................................... 78 5.3.2.4. Load combinations .................................................................................................... 79 5.3.2.5. Construction scenarios considered ............................................................................ 79 5.3.3. FEA modelling and analysis .......................................................................................... 80 5.3.4. Results for Check 1: Self-weight only, no construction support and no phasing .......... 80 5.3.5. Results for Check 2: Construction phasing but no construction supports ..................... 81 5.3.6. Results for Check 3: Construction phasing and construction supports ......................... 82 5.3.6.1. Possibility of cracks during construction ................................................................... 82 5.3.6.2. Possibility of instability due to interface tensions during construction ..................... 83 5.3.6.3. Deflections and Bending moments ............................................................................ 85 5.3.7. Results for Check 4: Wind Load ................................................................................... 86 5.3.8. Results for Check 5: Snow load .................................................................................... 87 5.3.9. Photo montage of case study ......................................................................................... 88 5.4. OTHER APPLICATIONS OF FRAMEWORK ................................................................... 88 5.4.1. Exhibit A ....................................................................................................................... 88 5.4.2. Exhibit B ........................................................................................................................ 90 5.4.3. Exhibit C and Photo Montage ....................................................................................... 91 6. CONCLUSION ................................................................................................................ 95 REFERENCES......................................................................................................................... 97 LIST OF ACRONYMS AND ABBREVIATIONS .............................................................. 101 APPENDICES ....................................................................................................................... 103 APPENDIX 1: PYTHON SCRIPT FOR DIANA AUTOMATIC PROPERTY ASSIGNMENT AND CONSTRUCTION PHASING ........................................................................................................ 103 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 15 1. INTRODUCTION 1.1. Scope and motivation Previous research showed that the construction industry is lagging in productivity and growth compared to other industries. This can be addressed with digitalisation of processes e.g. through incorporating Building Information Modelling (BIM) as well as the use of modular or off-site construction systems. Advantages of this include shorter construction and operational costs; reduced construction time; fewer unexpected costs for the client due to unforeseen issues on site; reduced energy consumption and better structural performance (Long et al., 2014; Bertram et al., 2019). It is well documented that the main construction material, concrete, is a major contributor to greenhouse gas emissions (Belton, 2021). Additionally, even though no other material has been found to be more efficient for use in construction than concrete, steel reinforcement leads to corrosion, expansion, cracking and then deterioration of the concrete itself, thereby limiting the durability of reinforced concrete structures. However, the use of reinforcement is compounded when concrete structures are designed in a way that may be perceived as “unnatural”. With the use of form-finding, a “natural” compression-only shape (see Figure 1) can be found that can limit the use of reinforcement. Such shapes have been built before but with the aid of expensive formwork during construction (Adriaenssens et al., 2014). Figure 1 – Compression-only shell structure - Aichtal Outdoor Theatre in Germany (Adriaenssens et al., 2014) Various researchers have been looking into ways to optimise the current construction systems using precast and/or form-finding (Dallinger and Kollegger, 2008; Pedersen, Larsen and Pigram, 2015; Borg Costanzi et al., 2018; Bao and Li, 2020). Realisation of the right construction system will assist in achieving the United Nation’s Sustainability Development Goals including “Sustainable Cities and Communities” and “Industry, Innovation and Infrastructure” to build sustainable and resilient infrastructure (United Nations, 2015). Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 16 There is work being done into optimising concrete mix and using more sustainable materials. This can be achieved for instance by substituting cement (whose production is carbon intensive) with fly ash from the coal industry or the slag from blast furnaces for improved strength and durability. Another (expensive) way is to physically capture the carbon produced during cement production and store it elsewhere (Belton, 2021). Other prefabrication manufacturers use steel reinforcement to connect precast elements such as the Lock Block company (Lock Block, 2021) which limits their durability. Various limitations of the proposed design and construction systems exist as discussed forthwith. For example one author uses a procedure for form-finding with complex textual programming that cannot easily be followed other than by the originator (Vizotto, 2010). Some use BIM and an integrated approach but this is limited to the conceptual design stage (Gomes et al., 2018). Authors such as Kontovourkis et al. (2019) present a BIM-based computational design and optimisation framework using topology optimisation and incorporating construction considerations. Although they consider concrete modular elements, they do not consider construction supports required for shell structures. Additionally, they make use of a non-flexible formwork mechanism that is restricted to a Yshaped element only (Kontovourkis, Phocas and Katsambas, 2019) unlike the flexible mould for the formwork of shell structures proposed in other literature (Borg Costanzi et al., 2018). More recently, the Striatus Bridge in Venice’s uses extremely large concrete modules by 3D printing that require heavy lifting devices (Lomholt, 2021). On the other hand, Bao and Li (2020) propose the solution for the problem of connection and ease of assembly and disassembly of precast elements using much smaller brick-like components joined by pre-stressing cables. However, they neglect the optimisation aspect by not considering compression-only and form-finding structures (Bao and Li, 2020). The Perpectum concept (Azenha, 2019) theorized but not implemented in 2019, seeks to address the problems identified. A sustainable, low-strength concrete precast compression-only structure that is virtually self-supporting during construction, is proposed (refer to Figure 2). This is achieved through a construction system whereby non-metallic cables connect the panels sequentially, during construction. Moreover, the panels are proposed to be sized at 1m x 1m x 0.3m such that they only require light lifting devices. Figure 2 - Set of assembled panels as proposed by Perpectum (Azenha, 2019) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 17 The current work further develops on Perpectum and addresses limitations of current systems as detailed in the objectives. 1.2. Objectives and methodology This study proposes a new collaborative BIM-based, sustainable compression-only structural block construction system. Each discrete part (block) of the structure is made through flexible moulds that are adaptable to a wide range of geometry. The parts are connected by prestressed cables which will be installed in-situ thereby creating a new construction system. The system further satisfies the following: i) self-supporting or few supports during construction ii) optimised i.e. compression-only system iii) durable and long lasting with no steel reinforcement (prestressing cables made of a distinct nonferrous material). For the purposes of evaluating the proposed construction system, the objectives of the study are as follows: • perform parametric modelling, computational design, and form-finding to produce a tessellated compression-only structural shape • define a construction sequence using cellular automata principles • define interoperability tools between the computational design program and BIM platform as well as between the BIM platform and (Finite Element Analysis) FEA software • create a BIM model from the structural shape in the computational design program • define the structural model from the BIM model and perform FEA to assess the structural behaviour of the construction system • define a BIM-based framework for collaborative design between the structural engineer and the architect Accordingly, the methodology entails the use of computational and parametric design to create a compression-only shell structural shape through the particle spring form-finding method. Once the overall structural shape is obtained, it is tessellated to define its discrete elements. Thereafter, FEA is used to assess the structural behaviour based on the construction sequence. Finally, a collaborative framework is presented such that the engineers and architects can work together to define and construct the most optimal structural shape in a BIM environment. It is finally remarked that this dissertation does not address the technological aspects needed for the prefabrication of the modules for the system, neither from the point of view of the flexible moulds, nor from the point of view of the adaptable parts needed to materialize the hollow parts for the cables to pass. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 18 1.3. Structure of dissertation The layout of the thesis is as follows. Chapter 2 presents a literature review of sustainability and optimisation in the design and construction of shell structures. The principle of Perpectum, which was the inspiration for this work, is presented. This is followed by a general discussion on shell structures and modular construction systems. Next, these principles are refined and distilled with examples incorporating BIM processes and workflows. Chapter 3 presents the parametric modelling and computational design methodology in this study using a simple example to explain the procedures. Rhinoceros 3D and plug-in Grasshopper 3D are used to conduct the form-finding and create the cellular automata algorithm for obtaining the construction sequence. A description of the connection tool from the computational design software to BIM platform is presented. The last section of this chapter shows photos of the 3D printed version of the example. Chapter 4 describes the interoperability tool defined for the BIM platform to structural analysis connection. The chapter has a discussion on some of the properties to be used for the structural analysis in the software DIANA FEA. Subsequently, the script for automating the material property assignment and construction phasing is presented. Chapter 5 presents the framework describing the collaborative workflow between the structural engineer and the architect to perform the design to produce the compression-only construction system. Thereafter, the framework is enacted with a case study including the parametric modelling, BIM, finite element analysis and results. Other applications of the framework are also briefly presented. Finally, Chapter 6 concludes the work and presents recommendations and future work proposals. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 19 2. SUSTAINABLE DESIGN AND CONSTRUCTION OF SHELL STRUCTURES USING DIGITAL PROCESSES & TECHNOLOGIES 2.1. Introduction In recent decades, the construction industry has been criticized due to its continued use of high energyconsuming materials such as steel and concrete in a manner that is wasteful and neither optimised nor sustainable thereby limiting its productivity (Ribeirinho et al., 2020; Belton, 2021; Webb, 2021). Moreover, unlike other manufacturing industries that have embraced digitisation and automation, the construction industry lags behind and has made little progress on this front (Barbosa et al., 2017). As a result, the construction industry has been limiting itself in terms of productivity and growth thereby lagging far behind the manufacturing sector as well as the total economy trend as shown in Figure 3. Figure 3 – Construction labour-productivity vs. manufacturing and total economy growth trend (Barbosa et al., 2017) The construction index of real gross value added per hour worked, only improved from 100 in 1995 to 110 in 2014, while manufacturing improved from 100 to almost 200 in the same time frame. Similarly, the compound annual growth rate for manufacturing was 2.6% higher than for construction in the same period. In fact, according to a study by the McKinsey Global Institute think tank (Ribeirinho et al., 2020), the construction industry contributes 8% per year to greenhouse gas emissions compared to the aviation industry’s much lower 2.5% (Ribeirinho et al., 2020; Belton, 2021). Other critical aspects of modern construction materials are their durability and life cycle. For instance, concrete has been the main material used for construction (Belton, 2021). The reason for this is its mechanical properties and ease of production and ability to be moulded to the desired geometry. Although some concrete structures such as the Pantheon in Rome, Italy have been standing for more than 2000 years, modern concrete structures require the use of steel reinforcement in addition to the concrete to resist external loading effects. The problem is that steel reinforcement is prone to rust and this can happen when the concrete cracks and there is ingress of deleterious materials that reach the steel Manufacturing Construction Construction Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 20 (refer to Figure 4). This affects the durability of the entire structure and reduces its service life or increases rehabilitation and maintenance costs (Alexander and Nganga, 2014). Figure 4 – Photo example of corrosion-induced damage on a reinforced concrete marine structure (Alexander and Nganga, 2014) Despite the challenges identified, it is possible to make construction more productive without compromising on sustainability through a few simple principles (World Economic Forum, 2018). The first basic principle relies on optimising the construction materials by changing its constituents and selecting more durable materials and minimising steel reinforcing, by using better structural shapes such as shell structures. The second principle consists of using modular or precast construction systems thereby making the construction process faster and more efficient. The third principle relies on shifting from on-site construction to off-site prefabrication and controlled sequential construction. Finally, the fourth principle is based on incorporating digitalisation, automation and robotics and embracing related technologies such as BIM, 3D printing and Digital Twin technologies. In this regard, the present thesis has been inspired by, and developed within the framework of the ongoing research project called "Perpectum". Perpectum combines the Latin words “Perpectuum” meaning everlasting and “tectum” meaning shelter (Azenha, 2019). The concept of Perpectum aims to follow the four principles just mentioned as will be shown in the following chapters. This chapter reviews the current state-of-the art of shell structures, their sustainable design and how various authors are incorporating BIM digital processes in their design. It is therefore organized as follows. Section 2.2 outlines the Perpectum project. Shell structures are the basis of the Perpectum project due to their efficiency and the main structural system being researched and so Section 2.3 presents and discusses the main principles on which shell structures rely on. Section 2.4 focuses on modular construction systems for reasons discussed in this introduction. Sections 2.5 and 2.6 combine the topics presented and look at ways that they can be further optimised with computational design and BIM-based workflows applied to shell structures. 2.2. The principle of Perpectum Perpectum is a research proposal that addresses the various challenges that will be highlighted in the literature review including steel leading to reduced durability and the expenses related to use of Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 21 formwork when constructing shells and free-form structures. Perpectum results in a more efficient and cost-effective construction by using i) sustainable concrete with no rebar thereby avoiding corrosion and leading to indefinite durability ii) customisable moulds for concrete structural panels iii) permanent prestressing cables, and iv) Integrated Project Delivery (Azenha, 2019). Perpectum proposes the use of prefabricated concrete panels without rebar which are produced from customisable moulds. The panels can then be constructed sequentially using pre-stressed cables to produce compression-only free form shell structures – refer to Figure 5. Figure 5 – Perpectum panel concept and 3D printed proofs of concept (Azenha, 2019) The member connection is partly inspired by Dallinger & Kollegger (2008) who proposed precast textile reinforced concrete panels constructed using post-tensioning cables that pass-through ducts in the panels. The pre-stressing ensures stability during construction without the need for extensive and complex formwork or construction supports. Theoretically, this pre-loading would result in the structure being in compression with minimal deformation that acts like a single monolithic structure despite being made up of separate panels. Emphasis has also been placed on having enough pre-stress such that there is no tension at the interface between the panels which would cause instability of the structure (Dallinger and Kollegger, 2008). Additionally, the pre-stressing cables are not steel but rather maritime cables that are non-corrodible and will therefore be highly durable (Azenha, 2019). These principles will be expanded on further in the chapters that follow. 2.3. Shell structures 2.3.1. Definition, advantages and disadvantages Shell structures are large with a thickness much smaller than their other dimensions. They transmit forces primarily through a membrane action rather than bending moments. The advantages of shell structures are that, first, they are aesthetically pleasing, natural looking forms. Secondly, large open spaces and areas can be created without the need to use supports in between them. Third, due to their thinness, use of the membrane action and the high strength to weight ratio, the design is more efficient, and less material can be used, thereby making them more environmentally friendly (Adriaenssens et al., 2014; Zingoni and Enoma, 2020). Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 22 However, shell structures, particularly concrete ones, have some disadvantages which have led to their decline in use and popularity. The main reason for this is, the cost of the formwork which can be as much as a third of the total concrete cost on the project or 15% of the total construction cost. This cost is usually due to the difficulty and complexity in setting up and dismantling the intricate formwork and scaffolding (Nassar and Aly, 2012; Zingoni and Enoma, 2020) and is therefore significantly increased when it comes to shapes from form-finding processes (Tomás and Martí, 2010; Kontovourkis, Phocas and Katsambas, 2019) as shown in Figure 6. Figure 6 – Under construction and completed shell structure at the entrance of the Universal Oceanographic Park in Valencia, Spain (Tomás and Martí, 2010) Nonetheless, nowadays, innovative options for customisable formwork are being considered with the help of technology, computational design and inspired by the textile industry, but these are yet to become mainstream (Borg Costanzi et al., 2018; Popescu et al., 2021). Alternatively, there are suggestions to have dual purpose shell structures to justify the cost of the formwork (Zingoni and Enoma, 2020). Another disadvantage is that if the shell is too thin, buckling problems can arise. Studies suggest that this issue can be overcome by increasing the shell thickness, using a material with a higher elastic modulus or increasing the geometric curvatures (Tomás and Martí, 2010). The other challenge is how to produce the geometry of a shell structure that ensures optimal structural behaviour. This is where form-finding comes in. 2.3.2. Form-finding methods for obtaining shell geometry There are two main methods to design a shell structure with a funicular shape. The first concerns the use of mathematical formulas that lead to the definition of geometries based on parabolas, spheres etc. However, if these “unnatural” shapes are used, extra reinforcement or edge beams are required to overcome the hoop stresses experienced in some areas and avoid excessive cracking during the life of the structure. The second method uses form-finding processes either from numerical means or by physical models as was popularised by Heinz Isler and Antoni Gaudí. The latter method creates tensiononly geometries which can be inverted to create compression-only geometries inspired by Richard Waller’s statement “As hangs the flexible line, so but inverted will stand the rigid arch” and Hooke’s law of inversion. However, although useful for visualisation and conceptual design purposes, physical models have the limitation that the forces on the structure depend on the material and this cannot be easily factored into the process and therefore numerical calculations are required for verification. The alternative would be to create a scale replica of the structure, but this would be expensive. Advantages Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 23 of form-finding using numerical means are that it allows the consideration of material properties, computational design can be used, and more shapes can be found (Veenendaal and Block, 2012; Adriaenssens et al., 2014; Zingoni and Enoma, 2020). Form-finding can be described as an iterative process used to find the optimal shape (no bending moments, axial forces only) in an initial usually flat system (shell or grid) of particles, connected by springs, with certain boundary conditions and characteristics, by applying loads to the particles (refer to Figure 7). Essentially, the goal is to use the forces to find the form as opposed to traditional design methods that first start with the shape and then find the forces on the shape. Form-finding can be achieved traditionally, using methods such as the Particle Spring system, Dynamic Relaxation Method and Force Density Method (Adriaenssens et al., 2014; Congiu, Fenu and Briseghella, 2021). Figure 7 – Top and axonometric views for Form-finding example starting with a flat mesh/grid & supports at two opposite corners (Veenendaal and Block, 2012) The Particle Spring Method is a dynamic equilibrium problem where the particles are given a mass while the springs have a stiffness and length. Thereafter, loads are applied onto the particles which cause displacements of the particles and elongation or reduction of the springs. The goal is to iterate until equilibrium is achieved i.e. the sum of applied loads equates the sum of internal forces. Despite being a dynamic equilibrium method which are the most efficient in terms of CPU usage, the method is seen as being overly complex with its use of multiple parameters (Veenendaal and Block, 2012; Adriaenssens et al., 2014; Congiu, Fenu and Briseghella, 2021). Particle Spring Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 24 The Force Density Method is a geometric stiffness method whose underlying principle is the force density or tension coefficient which equates to force divided by the length of a bar. The method makes use of a linear system of equations. It initially involves the definition of the boundary conditions and the typology; this is followed by the definition of the force densities and the loads. These inputs are then used to calculate the displacements. The process is iterated until equilibrium is found. The method has the advantage that the material stiffnesses and properties considered are only considered at the end which makes it easier to compute. Nevertheless, the method has been criticised as not being constructable and being only suitable for preliminary purposes. Another criticism is that the “force density” coefficient is not an intuitive parameter compared to other well-known parameters such as forces (Veenendaal and Block, 2012; Adriaenssens et al., 2014). The Dynamic Relaxation Method was invented by Alistair Day. It is also a dynamic equilibrium method that makes use of nonlinear equations and the principle of Kinetic Energy (KE) with the nodes initially at rest (velocity, v = 0) and the KE = 0. Then a load is introduced to the system which leads to residual forces which depend on the axial forces and shear forces and leads to a new velocity and kinetic energy for each node. This is then used to calculate the new KE in the system and the process is repeated until convergence occurs where the new and old KE are the same i.e. equilibrium (Veenendaal and Block, 2012; Adriaenssens et al., 2014). Other form-finding methods exist in the literature such as graphic statics diagram subdivision (Akbarzadeh, Van Mele and Block, 2014), the Thrust Network Analysis (Rippmann and Block, 2013) which is a type of graphic statics, as well as shell structures topology design all of which focus on generating funicular structural shapes by using axial diagrams. Veenendaal & Block (2012) and Adriaenssens et al. (2014) provide a comprehensive study on the topic of form-finding. 2.3.3. Structural analysis Once the form (geometry) has been obtained, as explained in Section 2.3.2, the next step is to conduct the structural analysis. Structural analysis involves the determination of the internal forces in the structure due to the applied loads. The goal is to determine whether the structure has the capacity to support the loads based on the structure’s material strength and stiffness, supports and boundary conditions. For static structures this is done by satisfying equations of i) equilibrium of applied loads and internal forces ii) compatibility of displacements between elements iii) constitutive relations to satisfy the principles of stress and strain of the elements (Adriaenssens et al., 2014). The Finite Element Method (FEM) of structural analysis is most used due to its applicability to structures of different boundary conditions, shapes and sizes. It simplifies complex problems by focussing on a small part of the structure at a time. Basically, once the problem is identified in terms of the knowns and unknowns, the FEM procedure (refer to Figure 8) requires the structure under analysis to be idealised and split into small (finite) elements. Then the three equations described in the previous paragraph, are solved based on the loads on each element and its support and boundary conditions. Thereafter, the equations for each element are summed up to find the solution for the whole structure. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 31 Figure 14 - Result of form-finding using RhinoVAULT & Panelisation of shell (Hadilou, 2014) 2.5.2. Prefabricated sequential construction In recent years, many prefabricated sequential construction methods have been proposed. As an example, Bao & Li (2020) propose the use of LEGO-inspired sustainable structures that can be assembled or disassembled as per the structural requirements and most importantly, in a sequential way. The authors are advocating for precast and using the LEGO method to i) make the connection between elements quicker with dry joints, and ii) reuse structures by disassembling the elements and assembling them elsewhere (refer to Figure 15). Figure 15 - Illustration of LEGO-inspired blocks and assembled structure (Bao & Li, 2020) In contrast to wet joints, the use of dry joints means there is no need to wait for concrete to dry on site. What is more, the method makes the blocks re-usable and therefore more sustainable and cost effective. In this case they use what they call “bendable concrete” which resists tension rather than rebar for improved durability and increased structural efficiency. They also use post tensioned (PT) cables to reduce cracking and bolts for the connections (Bao and Li, 2020). The system seems to have some restrictions and flaws such as the cost of production of the concrete, applicability only to certain structures that have an overall rectilinear shape and the need for complex Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 32 algorithms to establish the correct assembly and disassembly procedure. The need for having customised moulds for each block also significantly increases the time required to produce the blocks. But the authors argue that the production time can be reduced in future with the use of 3D printing (Bao and Li, 2020). Companies like Lock Block Ltd and Shay Murtagh Ltd are at the forefront of the precast construction industry in Canada and Ireland & UK respectively. Lock Block Ltd is committed to sustainability and claim to use “100% recycled aggregates and sand”. They use block units with connection keys at the interface to ensure robustness which can be further strengthened by connecting them with rods. The panels apply to various structural types, such as retaining walls, tunnels, overpasses etc. They are also easily assembled and disassembled; are reusable and have the advantage that no expensive scaffolding is required for construction (Lock Block, 2021). Regardless, their panels and construction systems are limited to specific structural types and would not be suitable for the free-form structural types being discussed in this thesis. Figure 16 - Lock Block Products (Lock Block, 2021) In comparison, Shay Murtagh Ltd has a wider applicability than the Lock Block system. They focus on larger elements consisting of precast beams, box culverts, precast tanks, or bespoke precast concrete and buildings by defining the individual precast panels that will form the building. Moreover, they consider a holistic view and design optimisation, addressing some of the challenges mentioned in Section 2.4 such as space on site, cost, constructability, sustainability. For instance, they plan and optimise the sequence of construction based on panel manufacture time at the factory, transportation to site, space on site and installation time (Gomes, 2021; Shay Murtagh, 2021). However, the construction system sometimes involves grouting or wet connection and propping of panels that requires waiting for hardening before constructing the next levels. Figure 17 - Large precast concrete panels on a truck (Shay Murtagh, 2021) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 33 2.6. Collaborative BIM based workflows A collaborative BIM based workflow uses an integrated approach whereby multiple stakeholders in the AEC industry collaborate with digital tools and processes to design and construct a structure. This is particularly useful for complex shell structures as explained in this literature review. 2.6.1. Digitalisation Digitalisation is the integration of digital technologies in processes that were previously analogue mediabased processes. It is imperative for the AEC industry to embrace digitalisation to be more productive and increase innovation. It can be achieved with the use of BIM which will encourage collaboration and integration of multidisciplinary teams (World Economic Forum, 2018). For example, construction drawings in the past were drawn by hand and physically handed to the contractor to conduct the construction. Nowadays, the situation is completely different with the use of either Computer-Aided Design (CAD) or Building Information Modelling (BIM) processes to perform the same task, thereby optimising and making the process quicker and more efficient and minimising mistakes. In the same way, engineers used to design on paper. While this is still the case sometimes, often, the design is conducted on a computer using computer programs that automate and quicken the design process. Similarly, the prefabrication can be automated, as is done in the automotive industry, rather than done manually (Bertram et al., 2019). During construction, automation can also be achieved using technologies such as 3D printing. This will become important particularly in the construction industry is afflicted by labour shortages (Turner & Townsend, 2018) a gap which can be covered by digital manufacturing processes. Digitalisation is relevant because it also allows the concept of “building it twice” which reduces the possibility that mistakes are made that will affect the construction process. Chuck Eastman in his prescient work (Eastman, 1974) describes a Building Description System (BDS) which is a large digital database of objects and their properties and their relationships with each other representing objects in a real building. The BDS has the following properties (Eastman, 1974): • Change of item properties in one part of the drawing leads to automatic updates in all the other elevations, plans etc. ensuring efficiency and reducing redundancy found in paper drawings • Object-oriented (borrowed from programming with properties such as inheritance and abstraction) database rather than line-based with construction item libraries to choose from • Embedded metadata about the object provided by the manufactures for design, construction and facility management purposes • Numerical analysis of the building’s properties • No obsolete information, information is always available and current • Automation of quantity take-offs, building code checks and clash detection This is the basis for what is called BIM today. For instance, 3-dimensional models can be set up with object libraries available in proprietary modelling platforms like Autodesk Revit as well as online with manufacturers details. It is possible to include geometrical and metadata of objects and functionalities that dwarf the capabilities of CAD. The 3D model can have BIM uses such as MEP modelling, Structural Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 34 modelling, and analysis as well as Energy analysis and Facility Management. The goal of BIM is to bridge the islands or silos of automation of AEC disciplines and enable accurate and consistent communication and flow of information through all the phases of a project using a digital 3-dimensional model (World Economic Forum, 2018). 2.6.2. Computational Design, Formwork development and physical prototyping Kontovourkis et al., (2019) propose a computational design and optimisation framework linked to a customisable modular formwork and automated fabrication of shell structures. The goal is to minimise material waste, consequently reducing cost and the environmental impact of construction. The construction automation also leads to decreased material and energy consumption, as well as increased construction quality and accuracy. Their BIM-based workflow involving architects, engineers and contractors is presented in the form of the framework shown in Figure 18. Figure 18 – Overall framework and details of computational design optimisation steps (Kontovourkis et al., 2019) In their framework, the first part is the computational design optimization where the architect performs the form-finding of the structure. Secondly, the linear static structural analysis is conducted by the structural engineer in tandem with the topology optimisation and the parametric design by the architect. Third, once the geometry is finalised, the detailed design is carried out. Figure 19 - 3D printed shell prototype with hexagonal tessellation (Adriaenssens et al., 2014) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 35 This part also includes the tessellation process where the structure is subdivided into segments like the partitions of the shell of a tortoise. Though in this case the designer can select the type of shape of the units e.g. rectangular, hexagonal, isosceles triangles, etc. as seen in Figure 14 and Figure 19 (Kontovourkis, Phocas and Katsambas, 2019). In the study, the surface obtained from form-finding is tessellated into square cells that are then offset to form a 3D structure. Through topological optimisation, the square cell becomes a Y-shaped unit which is defined as reinforced concrete for the structural analysis. The next part is the development of the semiautomatic formwork mechanism that can adjust its shape according to the tessellated unit. Nonetheless, the mechanism that was developed for the formwork is limited to the Y-shaped concrete components in their study and is not configurable for other tessellated shapes (Kontovourkis, Phocas and Katsambas, 2019). A more sophisticated method presented by Borg Costanzi et al. (2018) uses 3D printing and allows the production of structures of any shape by casting its constituent concrete panels onto a flexible and adaptable mould rather than a flat plane – refer to Figure 20. Figure 20 - Schematic of adaptable mould (Borg Costanzi et al., 2018) The authors also make use of Grasshopper 3D to create the geometry and a custom workflow from design to production and assembly to create the structure. However, in the study the authors neglect to address the complexity of the required construction supports for shell or free-form structures. They also neither discuss the structural robustness of the solution nor the type of connection between the panels in detail (Borg Costanzi et al., 2018). The last part of the work by Kontovourkis et al. (2019) is the physical prototyping where each unit of the structure is brought to life through adjusting the shape of the formwork, casting the concrete then removing the unit from the mould, before assembling the units to form the structure. The authors envision that the units will be precast. Once on site, sequential construction of the units will occur with bracing and supports to hold the structure in place until is completed (Kontovourkis, Phocas and Katsambas, 2019). The main advantage of the proposed workflow is the form-finding and topology optimisation which ensures material optimisation. Another advantage is the semi-automated nature of the formwork for the Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 36 concrete casting and the use of precast panels to save on time and cost. Despite this, the paper contains a glaring omission which is that the complexity and expense of construction supports for shell structures is not addressed (Kontovourkis, Phocas and Katsambas, 2019). 2.6.3. An integrated framework for multi-criteria optimization of thin concrete shells In their work, Gomes et al. (2018) propose an integrated framework for collaboration of the architect and engineer to produce a conceptual design of a shell structure. The framework allows for a quick generation and structural assessment of different 3D shell geometries, including cost and safety considerations to assist in accelerated decision making – refer to Figure 21. Figure 21 - Interactive and iterative thin shell pre-design process (Gomes et al., 2018) The paper proposes a methodology composed of three interlinked and iterative processes. In the first process, the boundary conditions and other requirements are defined, and a form-finding process is carried out to obtain the first shell shape. In the second process, a parametric model is created that allows the first shape to be changed easily to assess how these changes affect the defined requirements. The third and final process is computational design, which allows the computer to come up with unique solutions that are structurally optimal (Gomes et al., 2018). This last process uses a genetic algorithm that is provided with an initial population of possible solutions to iterate through and mutate based on provided goals and constraints to output the most optimal solutions. In the study, the goals were optimal structural performance and minimisation of cost. The Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 37 final part of this process is selection of a final structural shape based on a structural analysis that meets all design requirements (Gomes et al., 2018). The study shows that custom tools are sometimes necessary to perform certain tasks that go beyond the capabilities of proprietary software. This can be achieved by accessing the proprietary software’s API and/or using programming languages such as C# and Python. In the study, a component was created in C# that can obtain geometry information from the modelling software and transfer it to the structural analysis FEM software automatically setting up and running the analysis then reverting the results back to the modelling software for optimisation. This interoperability is a key feature in a BIM workflow to prevent information loss and latency as well as quicken decision making (Gomes et al., 2018). The proposed framework emphasises the importance of communication between the architect and engineer throughout the process, to ensure that any potential problems are highlighted and dealt with timeously. The automation resolves some of the most tedious and repetitive tasks that are invariably a part of the design process so that architects and engineers can focus on conceptual design, engineering thinking and analyses of results. Nonetheless, the study is limited to the conceptual design stage only and it remains to be seen whether or how it would work in practise with other considerations such as formwork for construction of the shell structure (Gomes et al., 2018). Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 38 This page is intentionally left blank Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 39 3. PARAMETRIC MODELLING AND COMPUTATIONAL DESIGN TOWARDS MODEL GENERATION 3.1. Introduction Based on the Perpectum research proposal by Azenha (2019), this work proposes compression-only structures tessellated into precast panels cast on a flexible mould, with in-situ self-sensing prestressing cables. The panel size can be approximately 1m x 1m with 200mm to enable easy lifting without complex machinery required. A thickness of 300mm is selected preliminarily to assess structural performance. As seen in the literature review presented in Chapter 2, the technological aspect and modular fabrication could be available with the current technology (refer to Figure 20). Ideally, the prestressing cables employed in Perpectum, are low stress, non-metallic and cost-effective members made up of multiple layered and braided cables similar to those used in the marine industry. However, in this thesis, 20mm diameter steel cables are used to evaluate the validity of the proposed system. The construction system proposes sequential assembly of the concrete panels to maintain robustness during construction, similar to masonry construction (refer to Figure 11). Each concrete panel is prestressed in two directions as it is added to the structure to maintain stability. The idea is to have technology that allows the concrete panels to have external anchor heads for the post tensioning that are decoupled after stressing to allow the next concrete panel to be placed. In the age of BIM, the integration of parametric modelling and computational design processes is becoming a fundamental part of the design process and so it is with the proposed construction system. Thus, the objectives of this section are to explain the use of parametric modelling and computational design processes to create the structural shape, thicken and tessellate the structure and add the cable geometry; assign an assembly sequence to each panel using cellular automata and generate the BIM model. A regular, simple geometry is used for the description of the processes to simplify and focus on the explanation of the procedures. However, it is possible to define more complex geometries provided they have width of at least 4m, at least four sides and either line or point supports. The structure’s height depends on functional and architectural requirements. The chapter starts with an explanation of the vault design system (Section 3.2) followed by a general overview of the design procedure (Section 3.3). This is followed by Section 3.4 that explicitly describes the step by step implementation of the algorithm for the design, including the procedure for obtaining the construction sequence using cellular automata principles. The chapter ends with a description of the connection from the model generation software to the BIM platform (Section 3.5). 3.2. Geometrical concept for vault system A compression-only structural shape with supports on the ground or on walls can be achieved using parametric modelling and computation design from a form-finding process. Starting with an arbitrary planar geometry, it is possible to use point or line supports to constrain the shape - refer to Figure 22. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 40 Figure 22 - Parameters and constraints for form-finding for a generic rectangular shape - Top view Then, an upward load can be applied to the points restrained by lines with an assigned stiffness (springs), and through iterations to obtain static equilibrium and a compression-only structure. Using the generic rectangular shape shown in Figure 22, the main concepts, parameters, and constraints essential for the form-finding process are explained as follows: 1) The length, a and width, b can be increased or decreased. In fact, the curves representing these lengths can be linear or curved. 2) The size of x and y can be changed by changing the number of divisions in any one of the directions, as required. 3) Consequently, this leads to changes in the lengths of the springs and positions of the nodes. 4) Any of the points can be selected as supports; any of the lines can be selected as support lines. The supports do not change position whilst all other points can shift once the load is applied. 5) The loads are applied on the points. 6) The lines are assigned a spring stiffness that can be adjusted as required. Therefore, depending on the boundary conditions, an infinite number of structural forms is possible. As described in Chapter 2, the resulting structure can be divided into panels which can be post tensioned during construction to reduce the formwork required. The resulting structure from form-finding is more efficient in terms of the force distribution in the system. 3.3. Overview of parametric modelling and computational design workflow This section describes the parametric modelling and computational design workflow. The form-finding and construction sequencing procedures of the project were carried out through the Visual Programming Language (VPL) Grasshopper 3D that is executed within the Rhinoceros 3D version 7 (Rhino) Computer-Aided Design (CAD) software. Parameters a - Width b - Length x - Dimension y - Dimension Point Line b a x x x x y y y Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 47 The cable curves were further divided into four lists to separate the top and bottom (Figure 33) and, left and right cable curves (Figure 34) in each panel. The reason for this was to have labelling consistent with the labelling of the panels (see Figure 29). Figure 33 and Figure 34 depict the Top view of the example for easier visualisation. The panel in the left bottom corner is numbered “0” (see Figure 29) while the cables in the “0” panel will also be numbered “0” (refer to Figure 33 and Figure 34). 3.4.4. Creating the assembly sequence using a cellular automata algorithm The panels and cables presented in the previous sections were assigned an assembly sequence. Controlling the assembly sequence of the panels means they can be brought onto site in the order in which they are needed thereby saving time and money. Additionally, it also allows designers to generate multiple solutions and consequently optimize the forces on the structure during construction. The assembly sequence algorithm in this study was defined using principles from cellular automata algorithms. The method was selected for automating the assembly sequence because it was successfully used previously for a similar application on dam construction sequences (Fernandes, 2015) and for its use of decision-making based on previous information. Generally, cellular automata algorithms make use of a network of cells and their neighbours to change the status of the cell i.e. dead or alive, alternatively active or inactive, depending on simple rules based on how many of its neighbours have the same status (Herr and Kvan, 2007). In this case, the cells were related to the panels and the status refers to whether the panel has been placed on the structure during construction. The cellular automata algorithm was defined in Grasshopper 3D and run using the Anemone Plug-in which allows users to run loops. The Loop Start component has some input data which is then connected to and updated with data from the Loop End component. The user can specify the number of repetitions then use the reset button to run the loops. Once completed, the user can obtain the final data from the Loop End component as explained in Table 1 and illustrated in Figure 35. Table 1 – Grasshopper Cellular automata algorithm task description Task Description 1. Inputs The initial layout is defined and each cell is entered initially as “dead”. The number of iterations is set and the reset button is used to start the loop. 2. Loop Start Received inputs and exchanges information with the Loop End. 3. Find Neighbours Proximity component is used to find the number of neighbours based on the initial layout. 4. No. of live neighbours Used to calculate how many neighbours that each cell has. 5. Separate dead/live cells Sift component is used to separate the dead and live cells in each loop. 6. Dead cell test Checks whether a particular cell is dead depending on how many live neighbouring cells it has. 7. Live cell test Checks whether a particular cell is alive depending on how many live neighbouring cells it has and whether it was alive before. 8. Combine next gen. dead and live cells Combines information from Task 6 and 7 and inputs back into the system. 9. Merge old and new information Records information during each loop and enters that information back into the new loop. 10. Loop End Data can be obtained after the number of iterations specified have been run Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 48 Figure 35 – Grasshopper cellular automata algorithm using the Anemone Plug-in Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 49 The algorithm starts with a block of rectangular cells with the same number as the panels and the same sequential order. First, the neighbours of each cell is identified using the Proximity component in Grasshopper (Task 3 in Table 1) with example shown in Figure 36. This was setup by establishing the number of neighbours required and the radius which should be checked by the Proximity component. On the one hand, in the case of a maximum of 8 neighbours chosen within a radius of 1.5 a) Cell 0 has corner Cell 6 and adjacent Cells 1 and 5 as neighbours; b) Cell 17 has corner Cells 11, 21, 23, 13 and adjacent Cells 12, 16, 18 and 22 as neighbours; c) while Cell 14 has corner Cells 8, 18 and adjacent Cells, 9 13 and 19 as neighbours as depicted in Figure 36a, b and c respectively. a) Neighbours for Cell 0 b) Neighbours for Cell 17 c) Neighbours for Cell 14 Figure 36 - Neighbours for cells based on maximum 8 neighbours and radius 1.5 On the other hand, in the case of a setting with a maximum of 4 neighbours instead of 8 and within a reduced radius of 1.0, the results are completly different. Cell 0 will now have only adjacent cells 1 and 5 as neighbours; Cell 17 has adjacent Cells 12, 16, 18 and 22 as neighbours while Cell 14 has adjacent Cells 9, 13 and 19 as neighbours as illustrated in Figure 37. a) Neighbours for cell 0 b) Neighbours for cell 17 c) Neighbours for cell 14 Figure 37 - Neighbours for cells based on maximum 4 neighbours and radius 1.0 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 50 A lower number of neighbours was used for the purposes of this study to reduce and control the number of cells activated in each loop. The assembly sequence in this case requires connection with adjacent panels only and not corner cells for connection with the PT cables see Figure 5. The cellular automata algorithm was caried out by first setting all the cells as “dead” by assigning them a value of zero. Then for the following generation, selected cells were set as “alive” by assigning them a value of one. For subsequent generations, the algorithm checked the current status i.e. dead or alive (zero or one), of each cell for that generation and then decided whether to change its status or keep it the same. This was done by first establishing a particular cell’s neighbours (see Figure 37) and then checking the value of each neighbour (zero or one). Then the sum of the values of all neighbouring cells determined whether the cell in question would live (be assigned a value of one) or stay dead (value zero) in the subsequent generation. Dead cells only became alive once they were in the proximity of between one and three live cells. Once activated, live cells stayed alive for all subsequent generations. The activated (live) cells during each loop/run were recorded to form the assembly sequence. Changing the assembly sequence leads to changes in the forces on the structure during construction. The sequence of activation and hence the assembly sequence can be changed by adjusting which cells are activated or set alive first. For instance, starting with all dead (green) cells (see Generation 0 in Figure 38a) then activating (red) the innermost bottom and top cells at either end i.e. Cells 1, 2 and 3; 31, 32 and 34, results in generation 2, 3 and 4 shown in Figure 38b, c and d, respectively: a) b) c) d) Figure 38 - Cell automata activation sequence – inner panels activated first Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 51 This assembly sequence was then applied to the order of the panels and cables as seen in Figure 39. a) b) Figure 39 - 3D and Plan View labelled with Assembly Sequence (1) Alternatively, starting with all dead cells (Figure 40a) then activating the outermost live cells at the four corners i.e. Cells 0, 5, 4 and 9; 30, 25, 29 and 34, results in the sequence shown in Figure 40b), c) and d) as follows. a) b) c) d) Figure 40 - Cell automata activation sequence – outer panels activated first Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 52 This assembly sequence was then applied to the order of the panels and cables as seen in Figure 41. a) b) Figure 41 – Axonometric and Top View labelled with Assembly Sequence (2) 3.4.5. Connection and interoperability with BIM platform including level of information need An important part of the workflow is the connection of the geometry to BIM platform. While ArchiCAD or Tekla are possible candidates, Revit was the BIM platform used in the study partly because the “Rhino.Inside.Revit” plug-in provides bi-directional interoperability between Rhino and Autodesk Revit. After the modelling stage, the geometry defined in Rhino was “baked” to Autodesk Revit geometry using the “Rhino.Inside.Revit” plug-in. The advantage of using it is that any changes that are made in Rhino can be immediately updated in Revit without the need to re-do any work. The results before and after baking are seen in Figure 42 and Figure 43 respectively. Figure 42 - Rhino geometry in Revit before baking, axonometric view Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 53 a) Shaded graphic display with single panel displaced and highlighted b) Wireframe graphic display to show cables Figure 43 - Revit geometry low level of detail, axonometric view Depending on the project phase and level of information need required, the geometry can be updated, and more information added to the model accordingly for the purposes of BIM. The cable curves would be sufficient for a lower level of detail but for a higher one, openings and the thickened cables would have to be represented. The operation can be carried out in Grasshopper and transmitted to Revit via the same procedure described earlier in this section. For the example presented in this section, the results are depicted in Figure 44. a) Consistent Colors Visual Style with single panel displaced b) Wireframe Visual Style showing cable thickness Figure 44 - Revit geometry with higher level of detail, axonometric view Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 54 Metadata can also be added either using the Grasshopper interface Rhino.Inside.Revit plug-in or using the Revit interface to assign native Revit families, set materials etc. Other tools such as Geometry Gym’s Rhino-Revit IFC and Hummingbird can be used for converting Rhino geometry to Revit geometry. However, Hummingbird is only compatible with specific versions of Rhino and Revit and is not currently supported by the latest version of these programs. Similarly, Geometry Gym’s IFC conversion procedure from Rhino to Revit requires a license and does not provide direct bidirectionality like the Rhino.Inside.Revit plug-in which accesses the Revit API. Nevertheless, Grevit, a free Grasshopper 3D Plug-in is just as effective as the Rhino.Inside.Revit plug-in and also allows a workflow suitable for BIM but the component exchanges are limited to certain Revit family types such as beams, columns and slabs. 3.5. 3D printing The proposed construction system was assessed by 3D printing the blocks from the form-finding process described in this chapter (refer to Figure 45). Each block consisted of 4 openings, two in each direction, slightly offset from the centre to prevent them from clashing. A keystone was placed on the topmost blocks to accommodate the assembly sequence which started from the supports on either side of the structure to the keystone. The blocks were connected by elastic wire passing through the openings in place of the PT cables. Tensioning the blocks using the wires adjusts the structural shape into position as shown in Figure 46 and Figure 47 Figure 45 - 3D printed blocks before assembly Figure 46 - 3D printed blocks after assembly - Front view Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 55 Figure 47 - 3D printed blocks after assembly – axonometric view Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 56 This page is intentionally left blank Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 63 a) Stage 1 axonometric view b) Stage 1 Active parts information c) Stage 2 axonometric view d) Stage 2 Active parts information Figure 52 - DIANA Stages of construction 1 to 2 for four-panel example In Construction Stage 1 (Figure 52a and b), Block 1 and all its corresponding cables (Cables 1) are added to start the assembly sequence. Then in Construction Stage 2 (Figure 52c and d), Block 2 and its corresponding cables (Cables 2) are also added to the system. Afterwards, in Construction Stage 3 (Figure 53a and b), Block 3 and all its corresponding cables (Cables 3) are added to continue the assembly sequence. Finally in Construction Stage 4 (Figure 53and d), Block 4 and its corresponding cables (Cables 4) are also added to complete the construction of the four blocks. The PT cables ensures the connection and stability of the panels during construction. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 64 a) Stage 3 axonometric view b) Stage 3 Active parts information c) Stage 4 axonometric view d) Stage 4 Active parts information Figure 53 - DIANA Stages of construction 3 to 4 for four-block example As illustrated the process of manually adding a construction stage and activating each the blocks and cables is a laborious process. For this reason, an interoperability tool was designed to automatically perform the phased analysis with the assembly sequence related to the cellular automata algorithm. 4.5.2. Python scripting for DIANA The DIANA FEA User’s manual provides specific Python commands that are readable and executable by the DIANA API and can be used to automate certain tasks. Alternatively, the command console inside DIANA displays the Python commands for each action carried out in DIANA. For example, a Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 65 1m length, 1m height and 0.3m breadth block was defined and assigned the material concrete with Young’s modulus 30 MPa and mass density of 2500kg/m3 as per Figure 54. Figure 54 - DIANA single panel size 1m x 1m x 0.3m, axonometric view and properties The resulting Python commands are shown in Figure 55. Figure 55 - DIANA Example block properties and Python commands Moreover, for any model that is created, DIANA automatically creates a Python script showing the commands that can be used to create/alter a model. From these options, Python’s built-in capability to iterate and automate processes can be exploited through creating custom scripts to be run in DIANA. 4.6. Script for property assignment and construction phasing A Python script was created that automatically assigns properties to the geometry as well as specifies the sequence for the proposed construction system. The Python script created from the C# program described in Section 4.3, is run in DIANA and the geometry from Revit is reproduced. For simpler geometry, it would be relatively quick to manually define and assign materials, loads, and supports and then set up an analysis. However, as illustrated in Section 4.4 and Appendix 2, the process is tedious and time-consuming for increased number of blocks with multiple construction phases. In order to speed up the structural analysis process and simplify making changes, further textual programming to Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 66 automate some of the pre-processing including defining the material, supports and loading properties and assigning them to the curves and blocks is carried out as part of this work (refer to Figure 56). For instance, a script was created where the material “Concrete” is defined and assigned properties such as the compressive strength and then assigned to each block. Similarly, the material “Steel” is defined and assigned properties such as the Young’s Modulus of Elasticity and then assigned to each cable. The post tensioning load and the anchor positions is also assigned for each cable. By using textual programming, these values can easily be adjusted if required without too much difficulty. This is particularly useful in an AEC design environment where changes are bound to occur. Figure 56 – Part of Python script setting up properties The last part of the Python script involves relating the cables to the blocks such that the cables would be activated when the corresponding block is activated in the assembly sequence. Because of the way the assembly sequence was set up in the Chapter 3, the numbering is in the order required and the desired cable can easily be recalled as needed. This is done using iterations and the “for” loop. A single analysis is defined consisting only of the first block in the assembly sequence and its cables. The following analysis duplicates the previous analysis with the difference that the next block in the specified sequence (see Section 3.4.4) is activated and so on until the last block and its cables have been added. The full Python script is available in Appendix 1. #Set units setUnit( "LENGTH", "MM" ) setUnit( "FORCE", "N" ) #Create materials addMaterial( "Concrete", "CONCR", "LEI", [] ) setParameter( "MATERIAL", "Concrete", "LINEAR/ELASTI/YOUNG", 30000 ) setParameter( "MATERIAL", "Concrete", "LINEAR/MASS/DENSIT", 2.5e-09 ) setParameter( "MATERIAL", "Concrete", "LINEAR/ELASTI/POISON", 0.2 ) addMaterial( "Steel", "REINFO", "LINEAR", [ "FRLGTH", "NOBOND" ] ) setParameter( "MATERIAL", "Steel", "LINEAR/ELASTI/YOUNG", 200000 ) setParameter( "MATERIAL", "Steel", "FREELE/FRLGTH", 1 ) #add Selfweight addSet( "GEOMETRYLOADSET", "Dead load" ) createModelLoad( "Global Load 1", "Dead load" ) #add PT loads addSet( "GEOMETRYLOADSET", "PT load" ) createBodyLoad( "PT load", "PT load" ) setParameter( "GEOMETRYLOAD", "PT load", "LODTYP", "POSTEN" ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/TENTYP", "ONEEND" ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/FORCE1", 40000 ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/SHEAR", 0 ) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 67 5. FRAMEWORK DEFINITION AND CASE STUDY 5.1. Introduction As part of a typical BIM process and generally required in a BIM Execution Plan (BEP), it is important to know who does what, when and how i.e. roles, timelines and responsibilities for each team member involved in the project. This ensures that before the project starts, each project stakeholder is informed of the scope of work, standards, modelling requirements, what is expected of them and the timeline for the deliverables. Another important aspect is the Data Exchange process between disciplines encompassing the software being used, how the information is transferred between them and the useability of the information (interoperability). It is important to be aware of all this information before the beginning of the project. This is where a process map or workflow comes in. In this chapter, a workflow with a case study is presented with the aim of representing how the compression-only shell design and structural analysis of the proposed construction system would occur in an actual project. For the sake of simplification, the workflow is limited to a simple project where the client, an architect and a structural engineer are the only role players. It is assumed that there are no Mechanical, Electrical and Plumbing (MEP) requirements in the project and responsibilities such as detailing are performed by the architect rather than a draughtsperson. The starting point is a client brief describing the project requirements, which results in a completed BIM model with enough details to be handed over to the contractor for construction. Throughout the workflow, it is important that the structural engineering and architectural disciplines collaborate and provide continuous feedback to each other to prevent information latency. Similarly, the interoperability tools presented will prevent errors and information loss during the data exchanges. Consequently, this chapter firstly presents a collaborative framework definition whereby the processes described in Chapters 3 and 4 are incorporated into a design workflow in Section 5.2. Section 5.3 presents the realisation of the parametric design and structural analysis of a free-form compression-only shell structure based on the framework. Finally, further applications of the framework are presented in Section 5.4. 5.2. Framework for workflow with architect and structural engineer Preliminary concept sketches of the shell structure by the architect can be turned into a viable constructable structural shape through analysis and design performed by the structural engineer. The following is a presentation of a practical methodology or framework encompassing the work as described in Chapters 3 and 4 for how the actual processes and workflow can be achieved. The framework used for the case study in this chapter is shown in Figure 57. The figure makes use of Business Process Model and Notation (BPMN) and is inspired by the work of Gomes (2018) to describe the workflow for a compression-only form-finding design and structural analysis of the construction system. The main themes of Processes 1, 2 and 3 are the Geometry Definition, BIM modelling and Structural Analysis respectively. Each of the processes are presented in greater detail forthwith. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 68 Figure 57 – Framework for case study workflow Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 69 A zoom in of the first process i.e. Geometry Definition is shown in Figure 58. This is the most important process as its implementation affects the downstream processes. Figure 58 - Process 1: Geometry definition Initially, it requires the architect to obtain a brief from the client and produce the project scope (Process 1a) and preliminary concept sketch (Process 1b). Process 1b specifies Revit as the software of choice but since the sketch is only for discussion purposes, any suitable software can be used. This information is shared with the engineer (Process 1c) who then defines the preliminary parametric model by using Grasshopper 3D and performs form-finding in Kangaroo (Process 1d). Process 1 concludes with an agreed upon structural shape in Rhino and Revit (Process 1h) which relies on the collaborative effort from both the structural engineer and the architect (Process 1e-g). Due to the Rhino.Inside.Revit plug in, the Rhino geometric shape is then immediately available in Revit (Process 1h). Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 70 A zoomed in version of the BIM process is depicted in Figure 59. This process serves as the starting point for the construction model which is finalised in the third process. Figure 59 - Process 2: BIM The process involves the development of the Revit model by the architect (Process 2a) including defining the non-geometrical information and increasing the level of detail where required. This is based on information provided by the structural engineer and the project requirements (Process 2b). The result of Process 2 is a preliminary 3D BIM model in Revit (Process 2c). Finally, a zoomed in version of the third process namely Structural Analysis is shown in Figure 60. The function of this process is to evaluate the construction viability of the geometry defined in Process 2 with the proposed construction system. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 71 Figure 60 - Process 3: Structural Analysis The process makes use of the Revit model from Process 2c and the custom interoperable tools described in Chapter 4 (Process 3a) to recreate the geometry for the structural analysis (Process 3b). If only minor changes are required to the model, they are communicated to the architect (Process 3d) who produces the final BIM model to be used for construction (Process 3e). Otherwise, there would be a need to return to Process 1. The framework is flexible and adaptable hence the engineer is also free to amend the model if required such as changing support conditions including adding temporary supports or other loads during Process 3b. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 72 5.3. Case study of a new sustainable compression-only structural block construction system A case study is carried out to assess the theory and the proposed framework. The idea is to use the framework to create a compression-only structural shape from form-finding and asses the structural viability of the proposed construction system as mentioned before. An outdoor shading space at Parque da Cidade, in Guimarães, Portugal is proposed, similar to the one in Venice (Figure 11). The shell is expected to experience wind and snow loading. Preliminary sketches from the architect produce the Revit rendering in Figure 61 as a result of the client brief (Process 1c in Figure 58). Figure 61 – Preliminary sketch of Case Study from Process 1c 5.3.1. Parametric modelling Parametric modelling and computational design as described in Chapter 3, are conducted as part of Process 1. The starting surface is made up of two parallel long curves joined to two parallel short curves as shown in Figure 62. As explained in Section 3.4.1, support positions are chosen to be along the two short curves, then the surface is divided into springs and nodes where the force is applied – refer to Figure 63a and Figure 63b respectively. a) b) Figure 62 – Case study starting curves and resulting surface – Top view 14m 10m Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 79 A uniform snow load is also applied based on an estimated snow load of 2kPa as presented in Figure 73, assuming a persistent situation and non-drifted snow. The point of this is to assess how the structure responds to an increase in a uniform gravity load. Figure 73 – Uniform Snow load added to structure in DIANA 5.3.2.4. Load combinations The structure was checked for the load combinations shown in Table 3 based on the Eurocode with a load combination factor of 1 being used for the self-weight as the focus is on the variable loads wind and snow (load combination 1.5). All losses are assumed to already be accounted for and so the load combination for the PT load is also 1. Additional load combinations can be considered in future. Table 3 - Load combinations Combination Description Type C1 1.0*Self-weight + 1.0*PT Load Serviceability limit state C2 1.0*Self-weight + 1.0*PT Load + 1.5*Wind load Ultimate limit state C3 1.0*Self-weight + 1.0*PT Load + 1.5*Snow load Ultimate limit state 5.3.2.5. Construction scenarios considered Once the geometry, boundary conditions, loads and material properties and have been defined, the next step is to set up the analysis. Since there are 140 blocks, 140 stages are added for the staged construction analysis in DIANA with the first stage being the addition of the first block and Stage 140 representing the addition of the final block. Thereafter, the structural analysis is carried out as follows. The five checks performed to investigate the structure response to the construction sequence and loading with the self-weight included in all cases are presented in Table 4. The purpose of the first check is a general stability and baseline check of the structure. Neither construction phasing, temporary construction supports nor loads other than the self-weight of the structure are considered. The rest of the checks all take into consideration the construction phasing. Check 2 considers construction phasing but not construction supports. Checks 3, 4 and 5 consider the use of temporary supports during construction. 2kPa 2kPa 2kPa 2kPa Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 80 Table 4 – Construction scenarios No. Description Selfweight Wind Load Snow Load Construction Phasing Construction supports 1 Self-weight (SW) only Yes No No No No 2 SW + Construction Phasing (CP) Yes No No Yes No 3 SW + CP + Temp. Supports (TS) Yes No No Yes Yes 4 SW + CP + TS + Wind Yes Yes No Yes Yes 5 SW + CP + TS + Snow Yes No Yes Yes Yes The construction supports are removed after the final block has been added (Stage 141). Thereafter, two stages are added for the wind (Stage 142) and snow load (Stage 143). The first three checks are during construction and therefore are restricted to load combination C1 with only the self-weight and the PT load applied. The last two checks are preliminary Ultimate Limit State checks for load combinations C2 and C3 with wind and snow respectively. 5.3.3. FEA modelling and analysis In the FEA conducted (see Section 4.4), the structural materials are assumed to be linearly elastic and a staged construction analysis is performed. Equilibrium should be maintained, throughout the construction stages. A simplified model is being used rather than having anchor plates for the prestressing cables or interface elements to observe the stresses between the panels. However, there should be no tensile stresses at the interfaces to guarantee construction stability. With more sophisticated models (e.g. with interface elements added), tension could be acceptable if it is small and the equilibrium is maintained. Consequently, the results will focus on the tensile stresses and two checks will be performed. Firstly, whether the stresses will lead to concrete cracking and secondly whether the interface stresses will cause instability and loss of equilibrium during construction. According to the Eurocode 2 (EN 1992-1-1:2004, Design of concrete structures - Part 1-1: General rules and rules for buildings), given a concrete grade C30/37 the characteristic cylinder compressive strength is 30 MPa. For a fractile of 5%, the design tensile strength can be estimated as in Equation 1. fctd, 0.05 = 0.7 x 0.30 x 𝑓 ck 2/3 𝛾 = 1.35 MPa Equation 1 A quadrilateral mesh of size 75 mm was selected to reduce computational time. Although a smaller mesh size can be used, the results were judged to be sufficiently close to those of the smaller 50mm mesh using a small model. The mesh can be further refined in future to investigate these preliminary results. 5.3.4. Results for Check 1: Self-weight only, no construction support and no phasing The principal stresses S1 for self-weight of the structure only and no construction supports or phasing are displayed in Figure 74. The maximum tensile stress is 0.004 MPa and the maximum compressive stress is 0.046 MPa. Although not plotted here for the sake of brevity, Principal Stresses S2 and S3 are in the range -0.447 MPa to 0 MPa and the deflections are less than 0.05mm in all directions. The results are to be expected based on the optimised nature of the structure. However, this system would require extensive construction supports that would significantly increase the project cost as Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 81 discussed in Chapter 2. Therefore, the proposed construction system is investigated including construction phasing, supports and loading in the following Sections with Checks 2 to 5 (see Table 4). Figure 74 - Principal Stresses S1 - Self-weight only, no construction supports or phasing 5.3.5. Results for Check 2: Construction phasing but no construction supports The next check is with the self-weight and construction phasing but with no construction supports. The assembly sequence from the cellular automata is used to consider the effect of adding one panel at a time. The tension stresses on the structure increase as the number of blocks in the system increase. It is highest at the top surface, gradually decreasing with depth to the bottom surface. The maximum tensile stress is 2.04 MPa at construction Stage 140, in the region where assembly commences (Figure 75). Figure 75 - Principal Stresses S1 for Construction Stage 140 with no provisional supports Top surface Bottom surface > 1.35 MPa Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 82 The stresses on the structure appear as soon as a block is added and are therefore caused by both the construction sequence as well as the post tensioning in the added block. Although, there is tension on both the bottom and top surfaces of the blocks, the tension is higher on the top surface as would be expected for this type of structure. The highest tension is for principal stresses S1. Although, the stresses are still generally less than 0.1 MPa, there is more tension in the structure with the introduction of construction phasing than before (Figure 74) and some areas of tension are greater than 1.35 MPa and will likely cause cracking. Therefore, it is necessary to add provisional construction supports to the system. 5.3.6. Results for Check 3: Construction phasing and construction supports The third check is for load combination C1, with construction supports, and construction phasing added. This is the most important check as it evaluates how the structure behaves during construction of the proposed system. The construction supports are added along the middle centre of the structure as shown in Figure 70 and the structure is checked for possibility of cracking, interface stresses, deflections and bending moments. 5.3.6.1. Possibility of cracks during construction This check is to determine if the tension on the structure is enough to cause cracks i.e. are the tensions greater than the design tensile strength of 1.35 MPa? With the use of construction supports, there is a reduction in tension throughout the construction phases as seen in Figure 76 compared to Figure 75. Parts of the system are in compression, but most parts are in tension. From the early stages of the construction (Figure 76), the tension in the system is at a maximum of 0.41 MPa. The tension increases steadily with the addition of each block until the tension is at a maximum of 0.78 MPa in Stage 140 (Figure 77) as opposed to the Check 2 where it was more than twice as high at 2 MPa. Figure 76 – Principal Stresses S1 for Check 3 during early construction (1) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 83 Figure 77 – Principal Stresses S1 for Check 3 during construction (2) The maximum tension is generally less than 0.34 MPa in most areas from Construction Stage 1 to Stage 140 when the last panel is placed. However, there are points in the centre of the system at the corners of the panels that have higher tension (> 0.68 MPa) that are due to the provisional supports and in the regions where the cable anchors would be - anchor plates were not added to make the model lighter (Figure 77). These tensions will not be transmitted to the structure and will be taken up by the provisional support system and anchor plates. Nonetheless, it is evident that the tensions on the structure will not cause cracking as they are less than 1.35 MPa. 5.3.6.2. Possibility of instability due to interface tensions during construction The interface refers to the surface-to-surface connection between panels (refer to Section 4.2.2). This to evaluate the stability in the structure during construction and check the validity of the model. Since the structure is symmetric in two directions, the stresses will be similar for each half of the structure. The interface principal stresses S1 during Construction Stage 140 are shown in Figure 79 and Figure 80 with the former showing the long side and the latter showing the short side of the centre of the structure. In both cases, the level of tension increases steadily from outward to inward blocks of the slice. (In the construction sequence, the inner blocks were added first and therefore have higher tensile stresses). In reference to Figure 79 and Figure 80, generally, the outer block stresses are more than 90 percent less than 0.15 MPa. In the middle blocks, although they are less than ten percent of the cross-sectional area, the regions of tension with higher stresses increase to between 0.15 MPa and 0.29 MPa. Similarly, on the top blocks, less than ten percent of the area have tensions greater than 0.29 MPa. ≥ 0.68 MPa Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 84 Figure 78 – Central Interface stresses during Construction Stage 140 (1) Figure 79 – Central Interface stresses during Construction Stage 140 (2) Figure 80 – Block A Interface stresses at Construction Stage 140 Block A ≤ 0 MPa ≤ 0.15 MPa ≤ 0.44MPa 300mm ≤ 0.29 MPa Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 85 Overall, the interfaces have parts in compression and parts in tension during Construction Stage 140 as shown in Figure 78 and Figure 79. The tensile stresses along the vertical Block A (refer to Figure 78), are further illustrated in Figure 80 to demonstrate the tension force calculation procedure. Eighty percent of the interface area has tension of 0.15 MPa or less, while 5% has tension of 0.29 MPa or less and another 5% of the area has 0.44 MPa of tension. The most critical interface areas for other construction stages were selected by inspection. The interface surface area is approximately A = 1.1 m * 0.3 m = 0.33 m2. The tensile forces at the interfaces for the construction Stages 97, 106, 132, 135 and 140 are as shown in Table 5. Table 5 - Interface tensile stresses and forces at 5 Construction Stages Stage Tensile stress (MPa) Area Percentage (%) Fi = σ * A * % (kN) Total Tensile Force F (kN) 97 0.12 90 35.64 0.25 10 8.25 43.89 106 0.12 50 19.8 19.8 132 0.16 50 26.4 0.3 10 9.9 0.6 5 10 46.4 135 0.16 90 47.52 0.3 10 9.9 57.42 140 0.44 5 7.3 0.29 5 4.8 0.15 80 39.6 51.7 For Construction Stage 97 which occurs after the two parts of the structure have been connected, more than 90% of the interface area are in tension with tensile stresses of 0.12 MPa or less and 10% of the interface area having regions of tension greater than 0.25 MPa. As more panels are added in Construction stage 106, the area of tension is 50% with tensile stresses of 0.12 MPa or less while the rest of the interface is in compression. For the later construction stages 132 and 135, about 50 to 90 % of the interface areas are in tension of 0.16 MPa or less. Less than 10% of the interface area have tensions exceeding 0.3 MPa. The rest of the regions (about 40%) are in compression. To summarise this section, multiplying the tension stresses and their percentage of area on the interface gives the tensile force at the given interface for that construction stage. Generally, the tensile forces at the interface increase with increase in construction stage. The highest tensile force occurs at construction stage 135 with an approximate value of 58 kN. This is less than the force provided by the PT cables (2*40 kN = 80kN) at each interface. Therefore, the PT cables provide a counter force that is more than the tension at the interface and so no loss of equilibrium would be expected during construction. 5.3.6.3. Deflections and Bending moments The deflections were checked and found to be steadily increasing during construction but remained less than 0.5mm in all directions and all construction stages. A quick calculation based on the stresses and moment of inertia of the cross section (M= σ x I /y) suggest that the bending moment is less than 5 kNm. This is well below the moment capacity (Mun) of a 300mm thick unreinforced C30/37 slab as per the calculation results of Equations 2 and 3. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 86 fctd, fl = fctm x (1.6 - ℎ 1000 ) / γ Equation 2 Mun = fctd,fl x ( ℎ2 6 ) Equation 3 Mean axial tensile strength; fctm = 2.9 MPa Design flexural tensile strength of concrete; f'ctd,fl = 2.51 MPa Moment capacity per m of unreinforced slab; Mun = 38 kNm 5.3.7. Results for Check 4: Wind Load The fourth check is for load combination C2, which considers wind loading after construction. The principal stresses for S1 and S2 of the overall structure for this check are displayed in Figure 81 and Figure 82 respectively. Note that this is after the removal of the temporary construction supports. Figure 81 – Principal stresses S1 for Wind Load after construction Figure 82 - Principal stresses S2 for Wind Load after construction Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 87 The tensile stresses S1 (Figure 81) and S2 (Figure 82) are less than 0.34 MPa except in regions of the temporary supports where they are higher (0.67 MPa). This is much less than the design tensile stress of 1.35 MPa showing the unlikelihood of the structure cracking due to the loading. Principal stresses S3 for Check 4 are all in compression and between -2.14 MPa and -0.0 MPa. 5.3.8. Results for Check 5: Snow load The fifth check is for load combination C3, which considers snow loading after construction. The principal stresses of the overall structure for this check are displayed for S1 and S2 in Figure 83 and Figure 84 respectively. Note that this is after the removal of the temporary construction supports as well. Figure 83 – Principal stresses S1 for Snow Load after construction Figure 84 - Principal stresses S2 for Snow Load after construction Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 88 Similar to the wind load results, the tensile stresses S1 (Figure 83) and S2 (Figure 84) are less than 0.34 MPa except in regions of the temporary supports where they are higher (0.67 MPa). This is much less than the design tensile stress of 1.35 MPa so it is unlikely that the structure will crack due to the loading. Principal stresses S3 for Check 5 are all in compression and between -2.15 MPa and -0.05 MPa. 5.3.9. Photo montage of case study The photo montage shown in Figure 85 can be a real-life application of the case study presented in this chapter. The construction system is visible with the approximately 1 m x 1 m x 0.3 m concrete panels joined by PT cables in each direction. This illustrates the aesthetically pleasing aspect of the construction system. Figure 85 - Photo montage of case study, Parque da Cidade, Guimarães 5.4. Other applications of framework Three further structural shapes are presented to illustrate the versatility and variety of structural shapes that can be produced using the framework described in this chapter. 5.4.1. Exhibit A The first application (Exhibit A), results in an igloo-like structure (refer to Figure 86). Referring to Process 1, starting with an arbitrary planar surface and selecting some supports, the form-finding method can be carried out. The cables can then be added to the structure corresponding to the appropriate panel using the cellular automata algorithm and then the structure can be tessellated and thickened as desired (refer to Figure 86c and d). Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 95 6. CONCLUSION This work presented a collaborative BIM-based framework for a new sustainable compression-only structural block construction system. The introduction also included a description of the Perpectum concept (Azenha, 2019) which had been theorized in 2019, but never really implemented. It was followed by a literature review of sustainability and optimisation in construction and how this relates to shell structures and their sustainable design, including their incorporation into BIM processes. Subsequently, there was a description of the parametric modelling and computational design processes that were carried out. A simple geometry was used to explain the procedures, including the one for obtaining the construction sequence using customised cellular automata principles and a description of the connection tool from the CAD to BIM platform. Next, the interoperability tools defined for structural analysis connection with the BIM platform and the one for automating the construction phasing were described. Finally, there was a description of the proposed framework for collaborative BIM-based workflows for the compression-only structural block construction system. A case study was used to perform the procedures proposed in the framework including carrying out the computational design and form-finding (Process 1), producing the BIM model (Process 2) and carrying out FEA (Process 3). With the 3D printing of the case study, Technology Readiness Level (TRL) 2 and 3 could be said to have been achieved, with the technological concept ormulated, and an experimental proof of concept provided. The results based on the objectives in the introduction are as follows: • Using the visual programming software Grasshopper 3D in Rhino 3D, simplified Process 1. An understanding of the list system and nomenclature of the Rhino 3D platform is necessary to optimise the process. The “Food for Rhino” plug-ins can be used to further assist in carrying out the tasks required such as the form-finding (Kangaroo) and cellular automata algorithm (Anemone). Once the program has been set up, only minor adjustments are required to quickly make changes due to the parametric nature of the model. • In Process 2, Rhino.Inside.Revit provided direct interoperability from Rhino 3D to Autodesk Revit. Due to the requirements of the structural analysis software, it was necessary to first have the cables as lines. Thereafter, further computational modelling could be carried out to add openings and have the cable lines thickened for BIM modelling purposes. After that, metadata can be added to the model as required. • An interoperability tool was used which accessed the Autodesk Revit API via C# for Process 3. It automated the creation of a Python script that transformed the geometry from Revit nomenclature to structural analysis software DIANA nomenclature. Then, another Python script was created which automated the materials property assignment and construction phasing analysis in DIANA. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 96 • The structural analysis was performed for models with no construction supports, with construction supports, once the construction supports are removed and with wind, then with snow loading. The results show that: i) It is challenging to erect a precast structure without it having excessive tensile stresses likely to cause cracking, unless there are some provisional construction supports. But with the proposed construction system, very few supports are required when compared to the normal construction of a shell structure and more importantly, no in-situ complex formwork is necessary. ii) The construction sequence influences the tensile stresses that develop on the structure; hence the careful analysis of different scenarios is important. iii) The construction system results in tensile and compressive stresses generally less than 0.5 MPa meaning material mechanical property requirements are minimal, raising the possibility of using recycled material for concrete. iv) Tensile stress regions at the interface resulted in tensile force of up to 58 kN which is less than 75% of the applied PT load (combined 80 kN). Therefore, the structure is stable during construction. v) Adding non-symmetric loads onto the structure did not result in adverse effects and only slightly increase (<0.01 MPa) the total stresses on the structure. It is a structure with much higher tolerance to unpredicted loads that standard thin shells. It was also shown that the framework works for varying shapes and sizes and therefore can be used for a variety of structures and applications. For further work, more disciplines could be included in the framework such as the mechanical engineer and contractor. In addition, a more in depth look at the BIM modelling in Process 2 can be investigated including preparation of the documents for construction and how these would be linked to a factory for modular construction. Additionally, it would be prudent to include earthquake loading as well as more load combinations to test robustness of the structural shapes produced. Although the resulting stresses at the interfaces were relatively low, there were not expected at all due to the addition of the prestress. For this reason, further investigation into the connection or interface between panels would be required to ensure stability. Moreover, it would also be worth investigating if increasing the number of cables in each direction may reduce the tension at the interface. Furthermore, there is the need for technological developments to make the proposed system really viable especially related to the challenges in terms of the moulds and cable positioning in the prefabrication plant. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 97 REFERENCES Abdelmageed, S. and Zayed, T. (2020) ‘A study of literature in modular integrated construction - Critical review and future directions’, Journal of Cleaner Production, 277, p. 124044. doi: 10.1016/j.jclepro.2020.124044. Adriaenssens, S. et al. 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Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 100 Zingoni, A. and Enoma, N. (2020) ‘Dual-purpose concrete domes: A strategy for the revival of thin concrete shell roofs’, Structures, 28(November), pp. 2686–2703. doi: 10.1016/j.istruc.2020.10.067. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 101 LIST OF ACRONYMS AND ABBREVIATIONS AEC Architecture Engineering, and Construction API Application Programming Interface BEP BIM Execution Plan BIM Building Information Modelling CAD Computer-Aided Design DIANA FEA Displacement Analyzer Finite Element Analysis FEA Finite Element Analysis FEM Finite Element Method Grasshopper Grasshopper® 3D IFC Industry Foundation Class IGA Iso-Geometric Analysis KE Kinetic Energy MEP Mechanical, Electrical, Plumbing NURBS Non-Uniform Rational B-Spline PT Post-Tensioning Revit Autodesk Revit® Rhino Rhinoceros® 3D Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 102 This page is intentionally left blank Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 103 APPENDICES APPENDIX 1: PYTHON SCRIPT FOR DIANA AUTOMATIC PROPERTY ASSIGNMENT AND CONSTRUCTION PHASING ############################################################################## # Program to automate assignment of properties in DIANA # Python 3.7.3 # By Lombe Mutale with input from Prof. MA, Prof. BF & CG ############################################################################## setUnit( "LENGTH", "MM" ) setUnit( "FORCE", "N" ) #Create materials addMaterial( "Concrete", "CONCR", "LEI", [] ) setParameter( "MATERIAL", "Concrete", "LINEAR/ELASTI/YOUNG", 30000 ) setParameter( "MATERIAL", "Concrete", "LINEAR/MASS/DENSIT", 2.5e-09 ) setParameter( "MATERIAL", "Concrete", "LINEAR/ELASTI/POISON", 0.2 ) addMaterial( "Steel", "REINFO", "LINEAR", [ "FRLGTH", "NOBOND" ] ) setParameter( "MATERIAL", "Steel", "LINEAR/ELASTI/YOUNG", 200000 ) setParameter( "MATERIAL", "Steel", "FREELE/FRLGTH", 1 ) #add Selfweight addSet( "GEOMETRYLOADSET", "Dead load" ) createModelLoad( "Global Load 1", "Dead load" ) #add PT loads addSet( "GEOMETRYLOADSET", "PT load" ) createBodyLoad( "PT load", "PT load" ) setParameter( "GEOMETRYLOAD", "PT load", "LODTYP", "POSTEN" ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/TENTYP", "ONEEND" ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/FORCE1", 40000 ) setParameter( "GEOMETRYLOAD", "PT load", "POSTEN/SHEAR", 0 ) nB = 140 #ENTER NUMBER OF BLOCKS nC = nB*4 noOfBlocks = range(1,nB+1) noOfCables = range(1,nC+1) #noOfSupports = [1, 2, 3, 5, 9, 10, 19, 20, 21, 22, 35, 36, 37, 38, 55, 56, 57, 58, 79, 80] #ENTER BLOCKS WITH SUPPORTS or add manually in DIANA listSizeCables = len(noOfCables) noOfCablesInBlocks = range(1, nC, 4) rename( "SHAPESET", "Shapes", "Blocks" ) #ASSIGN CABLE PROPERTIES for Cn in noOfCables: setShapeType( "REINFORCEMENTSHAPE", [ "Cable"+str(Cn)] ) addGeometry( "Cable"+str(Cn), "RELINE", "REBAR", [] ) setParameter( "GEOMET", "Cable"+str(Cn), "REIEMB/CROSSE", 140 ) setReinforcementType( "REINFORCEMENTSHAPE", ["Cable"+str(Cn) ], "BAR" ) assignMaterial( "Steel", "REINFORCEMENTSHAPE", [ "Cable"+str(Cn) ] ) assignGeometry( "Cable"+str(Cn), "REINFORCEMENTSHAPE", [ "Cable"+str(Cn)] ) #ASSIGN BLOCK PROPERTIES for Bn in noOfBlocks: setElementClassType( "SHAPE", [ "Block"+str(Bn)], "STRSOL" ) assignMaterial( "Concrete", "SHAPE", [ "Block"+str(Bn) ] ) #add Blocks to set moveToShapeSet( [ "Block"+str(Bn)], "Blocks" ) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 104 #ASSIGN BLOCK PROPERTIES for Bn in noOfBlocks: setElementClassType( "SHAPE", [ "Block"+str(Bn)], "STRSOL" ) assignMaterial( "Concrete", "SHAPE", [ "Block"+str(Bn) ] ) #add Blocks to set moveToShapeSet( [ "Block"+str(Bn)], "Blocks" ) #Relate cables to Blocks addSet( "GEOMETRYREINFOSET", "Reinforcements"+str(Bn) ) rename( "SHAPESET", "Reinforcements"+str(Bn), "Cables Block"+str(Bn) ) ASSIGN REBAR PROPERTIES for CBn in noOfCablesInBlocks: moveToShapeSet( [ "Cable"+str(CBn), "Cable"+str(CBn+1), "Cable"+str(CBn+2), "Cable"+str(CBn+3)], "Cables Block"+str(int(CBn/4+1)) ) #add loads - VERTICAL CABLES attachTo( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/PNTS1", "Cable"+str(CBn), [[ 4367.39, -1948.74, 11.7079 ]] ) #ADD COODINATES OF FIRST END attach( "GEOMETRYLOAD", "PT load", [ "Cable"+str(CBn) ] ) attachTo( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/PNTS1", "Cable"+str(CBn+1), [[ 4683.85, -1974.12, 11.7364 ]] ) #ADD COODINATES OF FIRST END attach( "GEOMETRYLOAD", "PT load", [ "Cable"+str(CBn+1) ] ) #add loads - HORIZONTAL CABLES attachTo( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/PNTS1", "Cable"+str(CBn+2), [[ 4074.08, -1703.99, 322.817 ]] ) #ADD COODINATES OF FIRST END attach( "GEOMETRYLOAD", "PT load", [ "Cable"+str(CBn+2) ] ) attachTo( "GEOMETRYLOAD", "PT load", "POSTEN/ONEEND/PNTS1", "Cable"+str(CBn+3), [[ 4093.40, -1453.85, 654.538 ]] ) #ADD COODINATES OF FIRST END attach( "GEOMETRYLOAD", "PT load", [ "Cable"+str(CBn+3) ] ) #Add supports addSet( "GEOMETRYSUPPORTSET", "Geometry support set 1") createSurfaceSupport( "Support 1", "Geometry support set 1") setParameter( "GEOMETRYSUPPORT", "Support 1", "AXES", [ 1, 2 ] ) setParameter( "GEOMETRYSUPPORT", "Support 1", "TRANSL", [ 1, 1, 1 ] ) setParameter( "GEOMETRYSUPPORT", "Support 1", "ROTATI", [ 0, 0, 0 ] ) #for nS in noOfSupports:#ADD MANUALLY IF NOT WORKING #attach( "GEOMETRYSUPPORT", "Support 1", "Block"+str(nS), [[1000, - 1000, -12.941931]] ) #setViewPoint( "ISO1" ) for Bn in noOfBlocks: #Generate MESH setElementSize( [ "Block"+str(Bn)], 100, -1, True ) setMesherType( [ "Block"+str(Bn)], "HEXQUAD" ) clearMidSideNodeLocation( [ "Block"+str(Bn)] ) #RUN ANALYSIS generateMesh( [] ) #runSolver( [] ) #showView( "RESULT" ) Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 111 6. Adding loads to the shapes Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 112 7. Adding supports Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 113 8. Adding analysis Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 114 9. Assigning mesh properties Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 115 The PT load, assigned to the post tensioning cables, is to be added to each analysis stage after generating the mesh. Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 116 APPENDIX 3: PART GRASSHOPPER CODE FOR FORMFINDING AND SHAPE GENERATION Cable lines generation procedure Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 117 Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 118