European review of performance indicators towards sustainable road bridge management

Q2 Q3 Review of the next generation of performance indicators for sustainable road bridge management 1Ana MandićIvankovićPhD Q4 Civil Engineering Department, Faculty of Civil Engineering, University of Zagreb, Zagreb, Croatia (Orcid:0000-0001-9411-8621) 2 Q5 Alfred Strauss Dipl.-Ing., PhD Associate Professor, Institute of Structural Engineering, Department of Civil Engineering and Natural Hazards, University of Natural Resources and Life Sciences, Vienna, Austria (Orcid:0000-0002-1674-7083) 3Helder Sousa PhD Q6Research and Innovation, HS Consulting, Matosinhos, Portugal; BGI, Brisa Group, São Domingos de Rana, Portugal (corresponding author: [email protected]) (Orcid:0000-0001-8310-0119) 123 Within the core of the European transport infrastructure, most roadway bridges have been built as part of the postWorld War II reconstruction effort, meaning society is already facing the beginning of the end of their lifetime. Hence, bridge management is becoming more and more influenced by life-cycle multiobjective performance criteria that need to be balanced wisely from a sustainability point of view. This is in line with the 2030 Agenda for Sustainable Development promoted by the UN in 2015 towards a sustainable planet. Q7 In this context, a holistic review, at the European level, is given of the different performance levels, supported by national practice codes, guidelines and research accomplishments towards (a) homogenisation of concepts, (b) linking between performance and management and (c) strengthening of the links between costs, reliability and sustainability. Based on this, a holistic framework for performance indicators is proposed supported by hierarchical categorisation and benefiting from the increased utilisation of structural health monitoring. This framework defines the basis for European training on bridge management by addressing some of the UN Sustainable Development Goals defined in the 2030 Agenda for Sustainable Development. Q8 Notation 1. Introduction According to the Fédération Internationale du Béton (Q9 FIB, 2010), the current engineering practice of conservation management is typically based on minimisation of costs (i.e. design, construction and conservation) to achieve and maintain minimum performance/ quality requirements. Nevertheless, this is subjected and exposed to diverse phenomena, which are highly dependent on how this framework of asset management is defined in order to guarantee a satisfactory asset performance throughout the entire lifetime. In this context, and narrowing down to the specificcaseofbridges,a satisfactory management framework might be defined as a function of several factors, such as safety, stability, serviceability, functionality, durability, cost-effectiveness and impact on the environment. Q10 This is in line with the UN Sustainable Development Goals (SDGs) defined in the 2030 Agenda for Sustainable Development signed, in 2015, by all countries in the UN towards a sustainable planet (UN, 2015), more specifically, among the 17 SDGs, the ones related to industry, innovation and infrastructure (SDG 9) and partnerships for the goals (SDG 17). According to Sachs et al. (2017), Europe shows significant discrepancies in terms of levels of achievement on these SDGs, with the majority of northern countries showing green levels of accomplishment, whereas several countries from central and south Europe reveal critical levels of accomplishment. Hence, it becomes evident the necessity and urgency of having a holistic and homogenised bridge management framework across all Europe, which, in the authors’ opinion, can be efficiently attained only by means of a joint effort at the European level (i.e. partnerships) based on a learning process, experiences and know-how that each country holds and never forgetting the science progress, mainly new technologies related to structural health monitoring (SHM) applied to bridges (i.e. innovation and infrastructure). An overview of current measuring approaches and methods along with the most critical aspects of bridge performance is presented by the Federal Highway Administration in the report of the LongTerm Bridge Performance programme (Hooks and Frangopol, 2013). In addition, a project report from the University of Wisconsin (Adams and Kang, 2009) gives an overview of bridge performance measures. At the European level and since 1995, the Organisation for Economic Co-operation and Development (OECD) has been carrying out a research on performance ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 1 Cite this article MandićIvankovićA, Strauss A and Sousa H (2019) Review of the next generation of performance indicators for sustainable road bridge management. Proceedings of the Institution of Civil Engineers –Engineering Sustainability XXXX(XXXX):1–XX, https://doi.org/10.1680/jensu.18.00052 Research Article Paper 1800052 Received 16/10/2018; Accepted 21/06/2019 ICE Publishing: All rights reserved Keywords: Q1bridges/sustainability Engineering Sustainability indicators (PIs) for the roads sector. Moreover, 15 PIs have been identified among those used by road administrations throughout the world (OECD, 2001). Most of these are related to road users’ satisfaction and asset management and can be viewed as socioeconomic indicators and are not merely related to assets. Q11 Recently (mainly during the past 10 years), further studies have been carried out towards evaluation of the performance of infrastructures and bridges from a holistic perspective by taking into account complementary criteria related to assets, mainly from the (a) environmental, (b) economic and (c) social points of view (Gervásio and da Silva, 2013; Serpell, 2015; Ugwu et al., 2006). Q12 With particular focus on pavement performance, the setting of suitable PIs from a base-level approach considering the combination of different procedures by means of weighting factors can be found in the report by European Cooperation in Science and Technology (Cost) Action 354 (2008). The main concept starts from a specific PI (e.g. related to one characteristic) and goes through combined PIs (e.g. related to two or more characteristics) until it reaches the level of general PIs (e.g. related to different factors, such as safety, user comfort and environment). With 1 particular interest, a scientific understanding about lifetime engineering allied with science-based advancement of sustainable construction in Europe was promoted during Cost Action C25 (Bragança, 2010; Cost Action C25, 2011). Although most of the results gathered in this Cost Action were building oriented, some examples of the life-cycle assessment of bridges can also be found. More recently, PIs in the context of infrastructure networks have been introduced by Ghosn et al. (2016), who concluded, by observation, the lack of explicit system-level design and operation performance and restoration goals for most lifeline systems. It is worth noting that bridge performance in Europe is dominated by PIs supported by operators’database, which are set by surveying documents related to bridge maintenance. Nevertheless, collection and analyses of available research-based PIs are starting to become more competitive since they can offer more accurate and objective information, which indeed encourages further research to improve performance assessment methods, mainly those supported by monitoring techniques. Based on the aforementioned guidelines and a survey of evaluation and inspection documents from different European countries, which can be found elsewhere (Cost Action 1406, 2014), it became clear that discrepancies in terms of concepts and terminologies exist. Therefore, a comprehensive and holistic approach to this problem – that is, a sustainablebridge management approach supported by a unified PI database –remains an ongoing task. Recently, Cost Action 1406 (2014) addressed an integrated approach, based on the state of the art of bridge performance at the European level, by considering (a) technical, (b) sustainability and (c) socio-economic aspects at three complementary and linked levels, (a) component, (b)system and (c) network levels, whereas the Cost Action 1402 (2014) aims to enhance the benefit of SHM by novel utilisation of applied decision analysis of how to assess the value of SHM –even before it is implemented in civil engineering structures in general. In the context of a joint effort between experts from both Cost Action TU1402 and TU1406, this paper aims to offer a review, by means of (a)identification, (b) evaluation and (c)quantification of PIs for road bridges towards a unified database of PIs, by benefiting from the rapidly advancing evolution of SHM. Firstly, the performance goals (PGs) and PIs are introduced and discussed at different levels within bridge management, mainly at the (a)component,(b) system and (c) network levels. This follows the reversed order of the process recommended generally in Q13reliability, availability, maintainability and safety analysis (Mahboob and Zio, 2018), which defines the end functions by setting goals and subsequently developing more detailed indicators. This is often also combined with performance-based design, and inversed verifications are made during this process. Secondly, the European PI database is reviewed and presented by dividing it into (a)an operators’PI database and (b) a research-based PI database. Thirdly, a categorisation of PIs is presented and described, according to the outlined performance levels and linking them to monitoring, mainly by presenting and discussing monitoring-based PIs. Finally, a discussion is promoted towards the identification of the most plausible trends for the next generation of PIs. The most relevant summary points conclude this work. 2. Performance 2.1 Performance goals Management of road bridges comprises coordinated activities to support their optimal value, which involves costs, risks, opportunities and PGs. Regarding the last ones, theses can be defined as properties which are required to be considered during the lifetime of a bridge. Moreover, for this characterisation, as a part of an efficient maintenance strategy, different types of PGs need to be used and at different levels. Consider the following example for the sake of clarity: the bending capacity of a bridge span. The functionality of the span is a PG –that is, at the component level –that influences directly the seismic performance of Q14the whole bridge –that is, at the system level –which is also a PG. Moreover, this last PG can also be considered as an input to the resilience of the roadway network where this bridge is inserted –that is, at the network level –due to the consequences of its collapse in the network functionality, which in turn is also a PG. Whether the PG is achieved or not, it may be assessed through the evaluation of various PIs at the possible different levels –that is, component, system and network levels (Figure 1). 2.2 Performance indicators In order to assess the accomplishment of a PG, a PI can be defined as a property related to a bridge characteristic that gives information about the condition of a bridge. This can be expressed in the form of either a dimensional parameter or a dimensionless index. The former is a measurable/testable quantitative parameter describing a specific characteristic related to the bridge performance (e.g. crack width on the bridge span), whereas the latter is a qualitative representation (e.g. the importance of span in the bridge structure or importance of the ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 2 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa bridge in the roadway network). In addition, thresholds and/or criteria need to be set in advance in order to allow interpretation of the value given by a PI and the subsequent decision-making approach. The former is a boundary region for (a) monitoring (e.g. an effect is observed or not), (b) assessing (e.g. an effect is low or high) and (c) decision-making (e.g. an effect is critical or not). On the other hand, the latter is a characteristic that is relevant for the choice between processes, such as maintenance actions or others ( Q15 Strauss et al., 2016). Hence, and for both concepts of PG and PI, threshold boundaries and/or setting the characteristics of criteria must be properly defined and quantified at the mentioned three levels: (a) component level (e.g. a span of a bridge), (b) system level (e.g. a bridge) and (c) network level (e.g. a group of bridges within a roadway network). 2.3 Component level Generally, bridge inspections are carried out by inspecting different Q16 components, which are grouped into three main subsystems: (a) substructure, (b) superstructure and (c) roadway. At the component level, the first goal (or task to be performed) is normally to assess the damage (Figure 1). Again, and for the sake of clarity, the example of reinforcement corrosion on the bridge span is used (Figure 2). Supported by FIB’s Model Code 2010 (FIB, 2010), the following four steps are set for solving a damage related to a specific deterioration process ■damage detection: physical disruption or change in the condition of a structure or its components, caused by external actions ■damage identification: ascertaining the cause of damage and its consequences ■damage evaluation: degree and/or extent with respect to the set threshold value ■damage assessment: detection of damages, including their identification and evaluation with respect to the set thresholds. Although setting an upper limit is the most common approach (step 3 in Figure 2), an additional threshold in damage assessment may be the duration of the damage phase by means of additional tests/measurements (steps 4 and 5 in Figure 2), which in turn give an indication in which phase (i.e. low, moderate or high) of the damage progress the element is found (step 6 in Figure 2). For example, for the first level of the damage progress (i.e. low), one might require protection from further progression; then, for the second level (i.e. moderate), one might require a repair action; and finally, for the last level (i.e. high), one might need a more detailed inspection/testing, which in turn might result in a further special repair (step 7 in Figure 2). For this, categorisation at the component level needs to be conducted first because different components might not necessarily use the same assessment criteria. For example, crack detection can be assessed differently depending on where it is found (e.g. span, pier or pile –Figure 1) and its width, orientation and origin. On damage assessment of a specific component, the utilisation of the damage index (qualitative scale of grades) is an indicator – that is, a PI –for the PG –that is, evaluation of the component functionality (Figure 1). Accordingly, the functionality of a bridge component (Figure 1) can be evaluated as (a) in the best condition, (b) with unquestionable function, (c) with function that has not been compromised and (d) with questionable function or element that is out of function (Table 1). It is important to mention that socio-economic aspects must also be included at this PI PG Optimal bridge management (c) Network level (group of bridges) (weighting factors) (b) System level (single bridge) (a) Component level (pile, pier, span etc.) Bridge importance Component importance Repair ranking Network functionality System functionality Component functionality (weighting factors) PI PG PI PI PI PI PI PI PG PG PG Condition assessment Component condition assessment Damage assessment Damage degree and extension Cost repair against cost replacement Performance indicators Performance goals Figure 1. The three levels within bridge management based on the concept of PIs and PGs ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 3 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa level. For example, going back to the example of the bridge span, the ratio between the sum of costs for repair of individual damages and the price for its replacement is a socio-economic indicator in the context of condition/performance assessment. Hence, and in order to support the decision-making process, a threshold can be set based on a quantitative scale. In order to assess the accomplishment of a PG, a PI can be defined as a property related to a bridge. 2.4 System level The purpose of determining the functionality level of a component is to assess the impact of the associated damage in the entire structure –that is, at the system level. For this, the following three PGs are considered: (a) structural safety and serviceability –SSS sys ; (b)traffic safety –TS sys ;and(c) durability –D sys (DIN 1076:1999 (DIN, 1999)). More specifically, SSSsys is, from a technical point of view, the main PG, whereas TS sys is a PG in the socio-economic context, and D sys is a PG that relates to environmental sustainability. In addition, the importance of each component can be set by means of weight parameters that are considered at the system level (Figure 1). For illustration and clarity, again consider the bridge span. Table 2 illustrates how the collapse of this component can affect the functionality of the system (i.e. the functionality of the bridge) according to different levels of impact. The scale in Table 2, which is merely qualitative, allows quantifying how the collapse of that component (e.g. the span) affects the system (i.e. the bridge). In addition to Table 2, Figure 3 illustrates how this relationship – that is, between functionality (Table 1) with traffic safety criterion (Table 2) –can be implemented for the case of two different types of components, mainly (a) an expansion joint (solid line) and (b) a curb (dashed line). With this simple example, it becomes clear and straightforward on how the component and system levels can be related. For instance, the collapse of an expansion joint (grade 4 on the horizontal axis) can lead to a complete traffic disruption (grade 4 on the vertical axis), whereas the collapse of a curb (grade 4 on the horizontal axis) might lead only to a local traffic redirection (grade 3 on the vertical axis). Moreover, this type of relationship can be expressed by an equation of the type given in Figure 3, where f com stands for the grade value associated with the component functionality and TS sys,max for the maximum value related to traffic safety. 2.5 Network level At the top level –that is, at the network level, the main goal is to assure the functionality of the network (Figure 1) by means of rational prioritisation and ranking of the required repair actions in critical systems (i.e. bridges). For this, and based on the practical experience in bridge management (HAC, 2008), the condition assessment (75% weight) made on the bridge condition (i.e. at the component and system levels) is now allied with the importance Table 1. Functionality levels for bridge components Level Component functionality, f com Observation 1 In best condition When no damage is detected 2 With unquestionable function When damage is in initial phase 3 With function that has not been compromised When damaged is moderate 4 With questionable function or out of function When damage has high degree and/or wide extent Assessment (decision) Evaluation (thresholds) Identification (type) Detection (anomaly) Additional tests required Quantification of area affected Inspection routine or special repair Critical deterioration process Delamination + corrosion Visual inspection Measurements (chloride content) 47 36 2 15 Time Figure 2. Assessment at the component level –damage evaluation process (example for reinforcement corrosion in concrete) ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 4 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa in the network (25% weight) of that same bridge (Figure 4). The condition assessment is based on four complementary indicators with the following relative weights: (a) structural safety and serviceability –30%; (b) traffic safety –30%; (c) durability – 10%; and (d) general bridge condition –30% (Bleiziffer et al., 2012; HAC, 2008). The importance in the network is based on other five criteria: (a) road category –25%; (b) annual average daily traffic–25%; (c) detour distance –25%; (d) largest span – 12·5%; and (e) total length –12·5% (Kuvačićand Jurić, 2005). For the latter, the values are set on the basis that the first three criteria are mutually independent and equally important, and the criteria of largest span and total length describe the common demands on the construction and property value, and by that, their importance in total may be considered as equal to other criteria. Further to this, these criteria are subsequently normalised (Figure 4) by using adequate analytical models and thresholds of indifference and preference. In other words, those criteria are normalised to comparable values with the help of preference functions and adequate threshold of indifference and preference for each criterion (Brans and Mareschal, 2005), which then can be used as a PI for the PG expressing the network functionality (Figure 1) –that is, optimal management plan by using the decision ranking and based on the power and weakness of the decisions (Brans and Mareschal, 2005; HAC, 2008). It may be noticed that this categorisation can occur naturally – that is, a parameter that is a PG in one step of the assessment procedure can become a PI in a higher level (Figure 1). Nevertheless, their categorisation into technical, sustainable and socio-economic indicators through component, system and network levels, as presented here, allows a rational basis and a much more straightforward approach towards the identification of methods for their quantification. 3. PI database in Europe As aforementioned, several guidelines focusing on PIs have become available. However, discrepancies in terms of concepts and terminologies between them have been found. Mainly, some PIs suggest including safety and serviceability but combine them with other PIs. On the other hand, serviceability is sometimes combined with durability in the performance category ‘structural Table 2. Maximum levels of the impact of the collapse of components on the system functionality Maximum level Structural safety, SS sys Traffic safety, TS sys Durability, D sys 1Noinfluence on the bridge safety: railing, curb, embankment and so on No influence on the trafficflow: cornices and so on No influence on the durability of other components: railing, main girder, arch, pier, foundation and so on 2Influence on a part of the bridge structure: cornices, cross-girders, bearing, wing and so on Speed limitation: sidewalk with barrier and so on Reduction in the durability of other components: expansion joint, pavement, curb, drain and so on 3Influence on the complete bridge structure: main girders, arch, pier, foundation and so on Local traffic redirection: sidewalk, embankment, curb, drainage and so on 4 Complete traffic suspension: barriers, pavement, expansion joint, roadway slab and so on Traffic safety, TSsys (system level) TSsys = 1 + TSsys,max –1 Functionality, fcom (component level) 4 4 3 3 3 2 2 1 1 Expansion joint Curb × (fcom–1) Figure 3. Assessment at the system level –impact of the component functionality (i.e. damage severity) on the system (example for traffic safety (HAC, 2008)) Condition assessment (weight = 75%) (weight = 25%) Traffic safety Durability General bridge condition Structural safety and stability Importance in the network Road category Annual average daily traffic Detour distance Largest span Total length 22·5% 22·5% 22·5% 7·5% 6·25% 6·25% 6·25% 3·13% 3·13% Figure 4. Assessment at the network level –performance criteria for priority repair ranking (based on Croatian Highways Ltd (HAC, 2008)) ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 5 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa condition’, whereas safety is combined with stability to form the performance category ‘structural integrity’. In addition, the indicators reliability and availability seem to be overlapping (Cost Action 1406, 2014). At the European scale and considering the current state of the art, an effective strategy needs to be thought and outlined in advance. Hence, the most representative PIs, used among several countries in Europe, were identified and selected from a comprehensive survey on the basis of a positive answer to following questions: (a) Is it measurable? (b) Is it quantifiable? (c) Is a target value available? (d) Is it valid for ranking purposes? (e) Does it allow any decision with economic implications? An expert group, composed of practitioners and researchers directly involved in bridge maintenance and management, was asked to specify PIs according to the aforementioned questions. Their feedback was properly systemised, and further information can be found elsewhere (Strauss et al., 2017a). In addition, the European PI database has been split into two complementary databases. These have been set according to different concepts and sources of information: (a) operators’PI database and (b) research-based PI database (Cost Action 1406, 2014). 3.1 Operators’PI database The survey confirmed what was already expected –that is, bridge performance in Europe is dominated by PIs that have been mainly developed by roadway operators. In this context, a subsequent survey was performed based on inspection and evaluation documents related to bridge maintenance, assessment and management, also collected from different countries in Europe. The Austrian national document related to quality assurance for structural maintenance (BMVI, 2011) and the guidelines on bridge condition indicators from the UK (CSS, 2004) were used as the bottom line for the proposed structure. In addition, a glossary has also been prepared on the basis of the information from the German document ( Q17 BAST, 2015). Further information on this can be found elsewhere (Cost Action 1406, 2014). The information gained might be structured as presented in Figure 5, which is available within the database by Cost Action 1406 (2014); Q18 the figure shows that the results are partly heterogeneous with a number of overlaps. This mainly results from the vague interpretation leeway and different know-how of the experts in the different countries. Hence, clustering of the several PIs was adopted to overcome this and with the ultimate objective of more easily identifying methods and procedures for revealing and quantifying PIs, as well as defining levels of their contribution to a specific PG. For sake of clarify and simplicity, four main groups of information were set ( Q19Figure 5): (a) performance level, (b) damage, (c) performance indicator/ index and (d) performance assessment. A reduction from more than the Q20700 PIs surveyed to 385 PIs (i.e. ≅50%) was achieved. The associated cut-out list is shown in Table 4, which satisfies the homogenisation requirements towards a European PI database (Cost Action 1406, 2014). It is worth noting that a parameter called condition rating, condition index or deterioration index, depending on which country/operator is referred to, has been identified as the most widely used PI (in all surveyed countries) in the context of visual inspections. Table 3 shows the typical index scale associated with and used by several European countries (Strauss et al., 2017). Q21 3.2 Research-based PI database Even though condition rating is the PI mostly used in practice by bridge owners and operators, some countries in Europe (e.g. Denmark and the Netherlands) have already moved forward in the utilisation of other PIs, which are more robust and informative. For instance, (a) concepts such as remaining service life, safety index reliability, vulnerability and robustness are becoming commonly used in Denmark (DRD, 2004), and (b) reliability, availability, maintainability and safety/risk, among others, are already being explored in the Netherlands to assess performance (Bakker et al., 2010). The concept of risk also deserves to be highlighted due to the fact that it can be used to define several new indicators, such as a social indicators, environmental indicators, economic indicators and/or political indicators (Rijkswaterstaat, 2012). In this sense, it becomes clear that continuous collection and surveying of research-based PIs complements and improves the General data spreadsheet Country-related data spreadsheet Name spreadsheet Country Document 1 Responsible person Name Author Type Year Inspection Evaluation Research ... ... ... ... ... ... ... ... ... ... ... ... ... ... Glossary spreadsheet Glossary Index Name Definition Reference Chapters/ paragraphs (a) Performance level (a) Level (a) System (a) Component (a) Material (b) Type (b) Characteristics (d) Performance assessment (c) Performance indicator/index (b) Damage Network System Subsystem Simple span Multiple span Frame Substructure Bearings Main girder Concrete Steel Wood Condition Process Sudden events Cracking Corrosion Flooding (c) Indicator (c) Detection (c) Evaluation (c) Index (d) Threshold (d) Goal (d) Criteria Crack width Cover Rating Measurement Evaluation Inspection In situ testing Analysis Catalogue Figure 5. European operators’PI spreadsheet database (Cost Action TU 1406, 2016) ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 6 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa Table 3. Rating system Rating index Description 1 No or very slight damage, normal age-related wear and tear, aesthetic damage. No decrease in load-carrying capacity, serviceability and predicted lifetime. No measures required. 2 Slight damage, production defects with no signs of further deterioration. No decrease in load-carrying capacity and serviceability. If no suitable measures are taken, the predicted lifetime will decrease. Repair measures are required during the next maintenance action. 3 Moderate to severe damage with no decrease in load-carrying capacity and serviceability. Signs of deterioration regarding load-carrying capacity and serviceability. Mediumterm maintenance and repair actions are necessary to preserve the serviceability and expected lifetime of the structure. 4 Severe damage, with no decrease in load-carrying capacity. Deterioration in terms of serviceability and expected lifetime can already be observed. Maintenance measures are to be instigated as soon as possible to safeguard the serviceability and the expected lifetime. Such measures may be substituted by additional special inspections within a defined time frame. 5 Extreme damage with impact on the load-carrying capacity of the structure. Repair and maintenance measures must be performed immediately. Table 4. Cut-out list of the main PIs within the European operators’PI database (Cost Action 1406, 2014) (continued on next page) Number Defects Material properties Equipment and protection Geometry changes Bearing capacity, structural integrity and joints Original construction and design Dynamic behaviour Environmentbased Rating Cost and importance Loads Sudden events 1 Concrete cover insufficient a Carbonation depth a Absence (missing) of equipment component Leaning Absent (missing) structural component Carrying capacity factor Damping a Environmental exposure Advanced deterioration process Element functionality level Permanent loading Erosion 2 Crack form/pattern a Cathodic protection deficiency Approach slab settlement Misalignment Arch ring separation Concrete cover a Frequency a Freeze–thaw Condition rating Bridge length Traffic loading Extreme traffic load a 3 Crack formation stage Chloride content a Asphalt pavement cracking Sag/deformation/ denivelation a Bearing deformation Design load Noise a Humidity a Damage degree/ extension Bridge span Extreme wind a 4 Crack length a Chloride depth profile a Asphalt pavement wearing and tearing (rutting, ravelling) Differential displacement a Bearing displacement Ductility Vibration level a Temperature a Deterioration index Detour distance Impact (e.g. of vehicles or ships) 5 Crack orientation a Concrete strength deficiency a Asphalt pavement wheel tracking and wrinkling and undulation Grouting deficiency Excessive strain a Vibrations/oscillations a Importance of the bridge in the network Importance of bridge element Rockfall 6 Crack spacing a Contamination (agent content) Blistering of protective coating Insufficient height of railing (safety barrier) Stiffness Inadequate clearance Price of the new element Scour a ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 7 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa Table 4. Continued Number Defects Material properties Equipment and protection Geometry changes Bearing capacity, structural integrity and joints Original construction and design Dynamic behaviour Environmentbased Rating Cost and importance Loads Sudden events 7 Crack width a Corrosion a Deterioration of protective coatings (e.g. corrosion protection) Joint deterioration Priority repair ranking Sum of costs for repair of individual damages Seismic activity of the area a 8 Cracks related to the origin (e.g. due to loading, due to settlement) Corrosion related to prestressing steel a Waterproofing deterioration/loss Loss of section (reduced section, section area absence) a Probability of detection Traffic restriction 9 Fatigue cracking Corrosion related to protective coating (corrosion stains) a Number of failed connectors (screw, bolt, rivet, weld etc.) Probability of failure Traffic volume (annual average daily traffic) a 10 Settlement a Corrosion related to reinforcement steel a Prestressing cable failure a Redundancy 11 Water penetrability Corrosion related to structural steel a Reinforcement bar failure a Reliability index 12 Wetting/leaking Fatigue (remaining service life) a Resistance Remaining service life 13 Galvanisation deficiency Thermal expansion a Resilience 14 Material characteristics Risk 15 Pitted corrosion Road category (roadway width) 16 Prestressing steel ductility deficiency a Robustness 17 Prestressing steel strength deficiency a Safety index 18 Reinforcing steel ductility deficiency a 19 Reinforcing steel strength deficiency a 20 Structural steel ductility deficiency a 21 Structural steel strength deficiency a a PIs that are increasingly monitored ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 8 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa existing operators’PI database, with a clear benefit on the modernisation of the management framework applied on the European roadway bridges. A detailed description on researchbased PI may be found within numerous research topics presented and published elsewhere (Cost Action 1406, 2014). Among research-based PIs, reliability index is of particular interest because is one of the best known and widely accepted research-based PIs, already included in some code regulations (Bergmeister et al., 2015; DRD, 2004). According to Ghosn et al. (2016), Strauss et al. (2017b) and Zambon et al. (2017), the targeted safety levels for this PI are set based on experience with the performance of existing structures, the consequences of member failures and the cost of construction. In addition to natural changes in loads and hazard patterns over time, structural components suffering from degradation mechanisms affecting their performance over time may eventually become subject to reduced safety levels. Indeed, this is already considered by reliability-based codes and standards. Nevertheless, the actual implementation in engineering practice and codified design depends on the availability of data, the type of application and the engineering community and industry –that is, one of the biggest challenges in the implementation of research-based PI database, as a complement to the operators’PI database, is to make it accessible to users and engineers from a practical point of view, which is not always the case yet. It is important to understand that to use this research-based PI –that is, safety index reliability – an adequate level of knowledge is required regarding the most important/critical characteristics/properties of the bridge (i.e. data). For instance, picking again on the example of the bridge span, the adequate level of knowledge might be related to the stiffness changes and/or the pattern of the traffic that crosses that bridge span. Hence, it becomes evident that additional investments (i.e. additional costs) might be required, mainly in the form of inspection with possible tests (e.g. example given in Figure 2), monitoring and/or advanced modelling techniques, for acquiring new data, which then can be used to update the existing knowledge. Moreover, these improved levels of knowledge, which indeed might be periodically/ continuously updated over the bridge lifetime, clearly holds the singular benefit of contributing to better decisions supported by reliable information. The question of what the best approach is to collecting new data arises naturally. Indeed, a parallel, but complementary, movement has been progressively taking place in the field of SHM systems. One of the most common applications found in the literature, in the civil engineering domain, is precisely on bridges. They are becoming a competitive solution –that is, in terms of costs against benefits –to supply additional, diverse and accurate information about the performance of existing/new structures over their lifetime. Nevertheless Q22 , the quantification of the benefits of these SHM systems prior to their effective utilisation remains a challenge under discussion (Cost Action 1402, 2014). This is perhaps the missing piece in order to support infrastructure owners and operators to consider them, as a complement to all other approaches, on a rational basis. On the other hand, it is also necessary to identify and categorise those PIs (Table 3) that may benefit, in terms of accuracy, from these SHM systems (e.g. corrosion progress, crack evolution, deflection evolution, fatigue damage evolution, score criticality, traffic loading) towards better characterisation of the main PGs, either at the component level, system level or network level (Cost Action 1402, 2014; Cost Actions TU1406 and TU1402, 2017). In this context, research-based PIs are a continuous process over time, where their maturity is continuously evolving and Q23is in accordance to the parameter readiness level to be explored further and used in the real field. 4. Structural health monitoring 4.1 Bridge monitoring According to Cost Action 345 (2004), bridge monitoring comprises standard inspection techniques performed periodically, following a regular maintenance plan, and continuous/periodic long-term measurements of time-variant measures with sensors installed at the structure. Today, it is possible to continuously and remotely monitor highly instrumented structures with a high degree of automation. Present solutions are versatile enough to allow for surveillance tasks to be carried out remotely in a costeffective manner (Chang et al., 2009; Sousa et al., 2011; Xu, 2018). As an example of a proactive and cutting-edge approach on this matter, monitoring is already being included, from some years now, as a standard mechatronic system in the design and construction of most large-scale and multidisciplinary bridge projects in Hong Kong and China (CECS, 2012; Wong, 2007). Several experts claim that if bridge monitoring could be designed and implemented as a complement to visual inspection, to enhance its effectiveness and mitigate its shortcomings, bridge owners would decide to take advantage of this new paradigm during the whole lifetime of the bridge –that is, from construction to operation and/or to demolition (Bas et al., 2018; Enckell, 2011; Pines and Aktan, 2002; Thöns, 2018; Vardanega et al., 2016; Zonta et al., 2014). Q24In the context of the bridge life cycle, two approaches are currently in practice: (a) periodical/short-term monitoring by using high sampling rates (e.g. up to 500 Hz), focusing on the operational conditions of the bridge, mainly on the observation of the in situ traffic loading patterns that each bridge is effectively subjected to, and (b) permanent/long-term monitoring with a modus operandi set to low sampling rates (e.g. up to hourly measurements), focusing on the trends related to climateand weather-related inputs, changes in the ground and soil and the movements of the foundations and the superstructure. 4.2 Periodical/short-term monitoring The implementation of weight in motion ( Q25WIM) is one of the most common applications of SHM with the objective of better characterisation of traffic loading into multilevel bridge ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 9 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa Jacob B and Loo H (2008) Weigh-in-motion for enforcement in Europe. Proceedings of the 5th International Conference on Weigh-in-Motion, Paris, France, pp. 15–24. Jacob B and O’Brien EJ (2005) Weigh-in-motion: recent developments in Europe. Proceedings of the 4th International Conference on Weigh-inMotion –ICWIM4, Taipei, Taiwan Q47 . KuvačićB and JurićS(2005) Bridge management system –determining and monitoring of the bridge condition and defining priorities and maintenance costs. Ceste i Mostovi 51:24–30 (in Croatian). Mahboob Q and Zio E (2018) Handbook of RAMS in Railway Systems: Theory and Practice. CRC Press, Boca Raton, FL, USA. MandićIvankovićA, SkokandićD, ŽnidaričA and Kreslin M (2017) Bridge performance indicators based on traffic load monitoring. Structure and Infrastructure Engineering 15(7): 899–911, https://doi.org/10.1080/ 15732479.2017.1415941. NjirićE and Šiljeg J (2018) Performance Assessment of Roadway Bridges for Priority Repair Ranking. Student scientific work. University of Zagreb, Zagreb, Croatia (in Croatian). OECD (Organisation for Economic Co-operation and Development) (2001) Performance Indicators for the Road Sector Summary of the Field Tests. OECD, Paris, France. Pines D and Aktan AE (2002) Status of structural health monitoring of long-span bridges in the United States. Progress in Structural Engineering and Materials 4: 372–380. Rijkswaterstaat (2012) Leidraad RAMS –Sturen op Prestaties van Systemen. Ministerie van Verkeer en Waterstaat, Hague, the Netherlands (in Dutch). Sachs J, Schmidt-Traub G, Kroll C, Durand-Delacre D and Teksoz K (2017) SDG Index and Dashboards Report 2017. Bertelsmann Stiftung and Sustainable Development Solutions Network, New York, NY, USA. Serpell J (2015) Sustainability Assessment of Road Bridges: Final Year Project Report. University of Bradford, Bradford, UK. SkokandićD(2016) Application of Bridge Weigh-in-Motion measurements in assessment of existing road bridges. ( Q48 MISSION, S. R. O. T.-S. T. S. (ed.)). Slovenian National Building and Civil Engineering Institute, Ljubljana, Slovenia. Q49 SkokandićD, IvankovićAM, ŽnidaričA and Kreslin M (2017) Application of bridge weigh-in-motion measurements in assessment of existing road bridges. Proceedings of the Joint COST TU1402–COST TU1406– IABSE WC1 Workshop (MandićIvankovićA, Matos JC, Thöns S and Høj NP (eds)). Cost, Brussels, Belgium. Sousa H and Santos L (2016) Long-term performance of prestressed concrete bridges. Proceedings of the European Workshop on Structural Health Monitoring –EWSHM 2016, Bilbao, Spain Q50 . Sousa H, Félix C, Bento J and Figueiras J (2011) Design and implementation of a monitoring system applied to a long-span prestressed concrete bridge. Structural Concrete 12:82–93. Sousa H, Zavitsas K, Polak JW and Chryssanthopoulos MK (2014) Inferring asset live load distributions from trafficflow data: a new SHM opportunity? Proceedings of the 7th European Workshop on Structural Health Monitoring, SHM 2014 –2nd European Conference of the Prognostics and Health Management (PHM) Society 2014, Nantes, France, pp. 435–442. Q51Strauss A, IvankovićA, Matos J and JC (2017a) Performance indicators for road bridges –overview of findings and future progress. Proceedings of the Joint COST TU1402–COST TU1406–IABSE WC1 Workshop (MandićIvankovićA, Matos JC, Thöns S and Høj NP (eds)). Cost, Brussels, Belgium. Strauss A, Wan-Wendner R, Vidovic A et al. (2017b) Gamma prediction models for long-term creep deformations of prestressed concrete bridges. Journal of Civil Engineering and Management 23: 681–698. Thöns S (2018) On the value of monitoring information for the structural integrity and risk management. Computer-aided Civil and Infrastructure Engineering 33:79–94. Ugwu OO, Kumaraswamy MM, Wong A and Ng ST (2006) Sustainability appraisal in infrastructure projects (SUSAIP): part 1. development of indicators and computational methods. Automation in Construction 15: 239–251. UN (2015) About the Sustainable Development Goals. UN, New York, NY, USA. See https://www.un.org/sustainabledevelopment/sustainabledevelopment-goals/ (accessed 14/04/2019). Q52Vardanega PJ, Webb GT, Fidler PRA and Middleton CR (2016) Assessing the potential value of bridge monitoring systems. Proceedings of the Institution of Civil Engineers –Bridge Engineering 169: 126–138. Wong KY (2007) Design of a structural health monitoring system for longspan bridges. Structure and Infrastructure Engineering 3: 169–185. Xu YL (2018) Making good use of structural health monitoring systems of long-span cable-supported bridges. Journal of Civil Structural Health Monitoring 8: 477–497. Zambon I, Vidovic A, Strauss A, Matos J and Amado J (2017) Comparison of stochastic prediction models based on visual inspections of bridge decks. Journal of Civil Engineering and Management 23: 553–561. ŽnidaričA, Kreslin M, LavričI and Kalin J (2012) Simplified approach to modelling traffic loads on bridges. Procedia –Social and Behavioral Sciences 48: 2887–2896. Zonta D, Glisic B and Adriaenssens S (2014) Value of information: impact of monitoring on decision-making. Structural Control and Health Monitoring 21: 1043–1056. How can you contribute? To discuss this paper, please email up to 500 words to the editor at [email protected]. Your contribution will be forwarded to the author(s) for a reply and, if considered appropriate by the editorial board, it will be published as discussion in a future issue of the journal. Proceedings journals rely entirely on contributions from the civil engineering profession (and allied disciplines). Information about how to submit your paper online is available at www.icevirtuallibrary.com/page/authors, where you will also find detailed author guidelines. ensu1800052.pdf 07/01/2019 9:59pmManila Typesetting Company16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 30 31 32 33 34 35 36 37 38 39 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 50 51 52 53 54 55 16 Engineering Sustainability Volume XXXX Issue ESXXXX Review of the next generation of performance indicators for sustainable road bridge management MandićIvanković, Strauss and Sousa Author Queries Q1: ‘Bridges and ‘sustainability’are the only valid keywords. Please add one more from the ICE Proceedings agreed list (https:// www.icevirtuallibrary.com/pb-assets/for%20authors/Main%20keywords%20November%202018-1542295908930.pdf). Q2: Please shorten the article title to 90 or fewer characters, including spaces. Q3: Please check changes in the article title. Q4: Please provide the job title for author Ivanković. Q5: Please check that the post-nominal qualifications and job title of author Strauss are presented correctly. Q6: Please provide job titles for author Sousa. Q7: Please check that changes in the sentence "In this context, a holistic review, at the European level ..." have preserved your meaning. Q8: Please provide a notation list (or a list of variables used in the text, equations, figures and tables, as well as their corresponding descriptions). Q9: As per ICE style, abbreviations that are pronounced letter by letter should be rendered as all capitals and those pronounced as words should have an initial capital only. Please verify that “FIB”is pronounced as “F-I-B”. Q10: Please check that changes in the sentence "This is in line with the UN Sustainable Development Goals (SDGs) defined ..." have preserved your meaning. Q11: Please check that changes in the sentence "Recently (mainly during the past 10 years) ..." have preserved your meaning. Q12: Please check that changes in the sentence "With particular focus on pavement performance ..." have preserved your meaning. Q13: "RAMS" has been expanded to "reliability, availability, maintainability and safety". Please check that the definition is correct. Q14: Please check change to “of the whole bridge”. Q15: Please add Strauss et al., 2016 to the reference list. Q16: Please check change to “different components, which are grouped into three main subsystems”. Q17: Please verify that “BAST”is pronounced as “B-A-S-T”. Q18: Please check change to “the figure shows that the results”. Q19: Please note that there is no panel b in Figure 5. Please check change of citation to “Figure 5-b”to “Figure 5”. Q20: Please check change of “700 IPs surveyed to 385 IPs”to “700 PIs surveyed to 385 PIs”. Q21: There are 2 Strauss et al. (2017) entries in the reference list. Please check if year of citation here should be “2017a”or “2017b”. Q22: Please check that changes in the sentence "Nevertheless, the quantification of the benefits ..." have preserved your meaning. Q23: The meaning of “is in accordance to the parameter readiness level to be explored further and used in the real field”is unclear. Please confirm that it is correct or amend the sentence for clarity. Q24: Please check that changes in the sentence "In the context of the bridge life cycle ..." have preserved your meaning. Q25: Please verify that “WIM”is pronounced as “W-I-M”. Q26: “B-WIM”has been defined as “bridge WIM”. Please check. Q27: Please check change to “400 PIs”. Q28: Please check the definitions provided for LVDT, GNSS, and FBG. Q29: "LDV" has been expanded to "laser Doppler vibrometer". Please check that the definition is correct. Q30: "RTD" has been expanded to "resistance temperature detector". Please check that the definition is correct. Q31: In Figure 6, KPI SRS ,KPI AM ,KPI C ,KPI E and KPI HP were changed to r SRS ,r AM ,r C ,r E and r HP , respectively, to match the text. Please check. Q32: Please check that changes in the sentence "This allowed better understanding of what PIs ..." have preserved your meaning. Q33: Please check that changes in the sentence "Looking carefully at Figure 8 ..." have preserved your meaning. Q34: The meaning of “the PIs underlined in fit within the holistic vision on system performance”is unclear. Please amend the sentence for clarity. Q35: Please check that changes in the sentence "In addition to Tables 5 and 6, Figure 9 summarises ..." have preserved your meaning. Q36: Please check the definitions provided for MEMS, GPR, and AE, abbreviations found in Figure 8. Q37: Please check that changes in the sentence "Indeed, new technological solutions are becoming so powerful ..." have preserved your meaning. Q38: Please check that changes in the sentence "In such a scenario, it is highly recommended ..." have preserved your meaning. Q39: Please provide page nos. or paper no. for Andriejauskas et al. (2013). Q40: Publication title in Bakker et al. (2010) was modified. Please check. Q41: Please provide issue no. and DOI for Bas, Apaydin, Ilki and Catbas (2018), Pines and Aktan (2002), Sousa, Félix, Bento and Figueiras (2011) Strauss, Wan-Wendner, Vidovic et al. (2017b), Ugwu, Kumaraswamy, Wong and Ng (2006), Vardanega, Webb, Fidler and Middleton (2016), Wong (2007), Xu (2018), Zambon, Vidovic, Strauss, Matos and Amado (2017) and Zonta D, Glisic and Adriaenssens (2014). Q42: Please provide page nos. or paper no. for Castillo et al. (2016). Q43: Please provide DOI for Chang, Yee and Lee (2009), Gervásio and Da Silva (2013), Kuvačićand Jurić(2005). Q44: Please provide page nos. for Cost Action 345 (2004). Q45: Please provide page numbers for Cost Actions TU 1406 and TU 1402 (2017) and verify that the provided publisher details are correct. Q46: The author list for Gonzalez et al. (2009) (originally Arches (2009)) was changed. Please check. Q47: Please provide page nos. or paper no. for Jacob and O’Brien (2005). Q48: Please amend “MISSION, S. R. O. T.-S. T. S.”to the correct editor name/list and provide book title and page nos. for Skokandić(2016). Q49: Details for Skokandićet al. (2017) have been modified. Please check. Please provide also page nos. for this reference. Q50: Please provide page nos. or paper no. for Sousa and Santos (2016). Q51: Details for Strauss et al. (2017a) have been modified. Please check. Please provide also page nos. for this reference. Q52: The entry for Vejdirektoratet (2004) was deleted as it was the same as DRD (2004). Please check.