Seminário de conclusão do projeto FRPLongDur

Seminário de Conclusão do Projeto FRPLongDur FRPlongDur POCI-01-0145-FEDER-016900 (PTDC/ECM-EST/1282/2014) Authors José Sena Cruz Luís Correia Ricardo Cruz Susana Cabral-Fonseca (E-BOOK DAS APRESENTAÇÕES ) ISBN 978-989-8793-12-6 © Departamento de Engenharia Civil – Escola de Engenharia – Universidade do Minho Todos os direitos reservados. Não é permitida a reprodução total ou parcial deste documento, nem o registo em suporte informático, nem a transmissão através de qualquer processo, eletrónico ou mecânico, sem a prévia autorização por escrito dos titulares dos direitos da edição. ii Index Preface Project FRPLongDur: Motivation, objectives, execution Durability of materials Durability of bond with EBR and NSM strengthening techniques Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques iv 1 21 58 72 iii Preface The FRPLongDur research project (reference no. POCI-01-0145-FEDER-016900) was financed by national funds through FCT and co-financed by the European Regional Development Fund (FEDER) through the Competitiveness and Internationalization Operational Program (POCI), and Lisbon Regional Operational Program. This project had as participating institutions at the University of Minho and the National Civil Engineering Laboratory. It also had the participation of Empa - Swiss Federal Laboratories for Materials Science and Technology. FRPLongDur aimed at contributing to the knowledge on the long-term behavior and durability of reinforced concrete elements strengthened with CFRP (Carbon Fiber Reinforced Polymers) laminates according to the EBR (Externally Bonded Reinforcement) and NSM (Near Surface Mounted) reinforcement techniques, under the effect of aging in a real environments. The work involved: (i) an extended experimental program, with the creation of five experimental stations distributed throughout Portugal country, involving different environments (Elvas, Guimarães, Lisbon, Serra da Estrela and Viana do Castelo), where test specimens at three scales (material, connection and structure) were installed to evaluate its performance during the time; (ii) the development of numerical simulations, based on the results obtained in the monitoring carried out; and, (iii) making recommendations for the project. On the last 30th of October 2020, the seminar to conclude the FRPLongDur project took place in a Webinar mode, in which the main results were presented. The present eBook summarizes the presentations carried out. The organizing committee José Sena Cruz |Luís Correia |Ricardo Cruz |Susana Cabral-Fonseca iv Project FRPLongDur: Motivation, objectives, execution José Sena Cruz Seminário de Conclusão do Projeto FRPlongDur (POCI-01-0145-FEDER-016900(PTDC/ECM-EST/1282/2014) October 30th, 2020 José Sena Cruz Institute for Sustainability and Innovation in Structural Engineering 2 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Technical Data Title: FRPLongDur – Long-term structural and durability performances of reinforced concrete elements strengthened in flexure with CFRP laminates Main Institution: UMinho Other patterns: National Laboratory of Civil Engineering (LNEC) Empa - Swiss Federal Laboratories for Materials Science and Technology Coordinator: José Sena-Cruz Team: J. Sena Cruz, S. Cabral-Fonseca, J. Michels, P. Fernandes, J.R. Cruz, J. Gallelo Martin, M. Rezazadeh, L. Correia, C. Czaderski Financing Institution: FCT - Portuguese Foundation for Science and Technology Reference: PTDC/ECM-EST/1282/2014 Period: June 2016 to October 2020 Budget: 199.983,00€ (127.579,00 to ISISE/UM) 2 Institute for Sustainability and Innovation in Structural Engineering 3Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Outline Motivation Objectives General methodology Dissemination/Outputs Acknowledgments Motivation 3 Institute for Sustainability and Innovation in Structural Engineering 5Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Motivation > Strengthening - Why? I. To eliminate structural problems or distresses which result from: unusual loading or exposure conditions; inadequate design; or poor construction practices. Distresses may be caused by overloads, fire, flood, foundation settlement, DETERIORATION RESULTING FROM ABRASION, FATIGUE EFFECTS, CHEMICAL ATTACK, WEATHERING, INADEQUATE MAINTENANCE, etc. III. To allow the feasibility of changing the use of a structure to accommodate a different use from the present one. II. To be conform to current codes and standards. Institute for Sustainability and Innovation in Structural Engineering 6 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Climatic changes: Increase in atmospheric CO2 levels Increase in the temperature Increase water levels Trends in the Construction Industry 10.8B US$ (2017) 17.5B US$ (2030) GLOBAL INVESTMENT (+62%) Motivation > Increased need of rehabilitation China, US and India (57% of this investment) The need of rehabilitation Accelerated expansion of the construction Unfavorable economic situation Low quality control requirements from the market New policies/actions: Green deal Circular economy Low-carbon economy 4 Institute for Sustainability and Innovation in Structural Engineering 7Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Motivation > Increased need of rehabilitation €305bn on rehabilitation and maintenance in 2012 (EU27) (European Construction Industry Federation 2013) “The Federal Highway Administration (FHWA) estimates that to eliminate the US nation’s bridge deficient backlog by 2028, we would need to invest $20.5bn annually, while only $12.8bn is being spent currently.” (ASCE Infrastructure Report Card 2013) INE, CENSOS 2011 Estado de conservação dos edifícios 1 milhão de edifícios Institute for Sustainability and Innovation in Structural Engineering 8 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Motivation > FRP systems as strengthening solutions The FRP’s has been used in Civil Engineering applications due to: Lightweight Good mechanical properties (stiffness and strength) Corrosion-resistant Good fatigue behavior Easy application Virtually endless variety of shapes Fiber Reinforced Polymer (FRP) materials 5 Institute for Sustainability and Innovation in Structural Engineering 21Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Objectives The FRPLongDur aims at contributing for the knowledge on long-term structural behaviour and durability performance of RC elements strengthened in flexure with CFRP laminates according to the EBR and NSM techniques, under various REAL ENVIRONMENTS, and compared this performance with the ones obtained by using artificial accelerated ageing protocols. EXPERIMENTAL ASSESSMENT •Different techniques •Different scales •Different environmental conditions MODELLING •Multi-physics •Short and timedependent ARTIFICIAL vs. REAL AGEING General methodology 12 Institute for Sustainability and Innovation in Structural Engineering 23Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Techniques, scales, experimental stations TECHNIQUES •EBR •NSM •MA & GA SCALE •Material •Bond •RC slabs EXPERIMENTAL STATIONS (6) •Reference Specimens (E1, E2) – UMinho •Ageing induced by carbonation (E3) – Lisbon@LNEC •Ageing induced by freeze/thaw attack (E4) – Serra da Estrela@EDP •Ageing induced by elevated temperatures (E5) – Elvas@S&P •Ageing induced by chlorides from sea water (E6) – V.Castelo@APDL Experimental Station E1,E2 E4 E5 E3 E6 Institute for Sustainability and Innovation in Structural Engineering 24 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Techniques, scales, experimental stations COMPOSITION •Chemical composition •Chemical resistance •Density •SEM MORPHOLOGY •Microscopy THERMAL PROPERTIES •DSC •DMA MECHANICAL PROPERTIES •Tensile properties •Flexural properties HYDROTHERMAL PROPERTIES •Water absorption EPOXY & CFRP LAMINATE 13 Institute for Sustainability and Innovation in Structural Engineering 25Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Techniques, scales, experimental stations SLABS – Evolution of Deflection FRP strain Concrete strain Bond degradation Aging (LAB - CB - CH - FT - ET) Year 6 Year 1 Year 2 Year 3 Year 4 Year 8 Year 10 Month 1 Month … Institute for Sustainability and Innovation in Structural Engineering 26 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Specimens’ preparation & Installation Concrete specimens: Single concrete mixture batch of 12 m2 C30/37 XC4(P) dmax12.5 S4 140 cylinders 150/300 90 cubes 200 mm of edge 90 cubes 200/200/400 [mm] 30 slabs 120/600/2600 [mm] Laminates: 258: S&P 101.4 [mm] 86: S&P 501.4 [mm] Epoxy adhesive: 342 Epoxy S&P 342 Epoxy Sika 14 Institute for Sustainability and Innovation in Structural Engineering 27Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Specimens’ preparation & Installation 1. Installation of the slabs 2. Installation of the bond specimens 3. Installation of the materials 4. Installation of the fencing Institute for Sustainability and Innovation in Structural Engineering 28 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Specimens’ preparation & Installation Experimental Station E4 – Seia/Barragem da Lagoa Comprida (EDP) 15 Institute for Sustainability and Innovation in Structural Engineering 29Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | General methodology > Specimens’ preparation & Installation Laboratory environments Outdoor environments E1@UMinho E2@UMinho E3@LNEC E4@EDP E5@S&P E6@APDL Dissemination/Outputs 16 Institute for Sustainability and Innovation in Structural Engineering 31Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Dissemination/Outputs Advanced training: PhD theses (1): “Multi-scale investigation on durability and long-term behavior of concrete structures strengthening with CFRP laminates according to the EBR and NSM techniques.” PhD Thesis of José Ricardo Loureiro Cruz, PhD Program on Civil Engineering, University of Minho. Master theses (4): “Exploring the use of hybrid FRP Composites on retrofitting of RC beam-column joints.” MSc Thesis of Zahir Mohammad Emtair Namourah, Advanced Masters in Structural Analysis of Monuments and Historical Constructions (SAHC), University of Minho. September, 2019. “Elementos de betão reforçados com laminados de CFRP: aderência e comportamento à flexão.” MSc Thesis of João Nuno Ferros Boaventura, Integrated Master in Civil Engineering, University of Minho. December, 2018. [in Portuguese] “Numerical simulation of RC slabs strengthened with pre-stressed CFRP laminates.” MSc Thesis of Gao Hongchen Jacey, Advanced Masters in Structural Analysis of Monuments and Historical Constructions (SAHC), University of Minho. July 2016. “Estruturas de betão armado reforçadas com laminados de CFRP: caracterização da aderência e do comportamento em flexão.” MSc Thesis of João Nuno Ferros Boaventura, Integrated Master in Civil Engineering, University of Minho. December 2016. [in Portuguese] Institute for Sustainability and Innovation in Structural Engineering 32 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Dissemination/Outputs ISI Papers in International Journals: (10) 1. Cruz, J.R.; Seręga, S.; Sena-Cruz, J.; Pereira, E.; Kwiecień, A.; Zając, B. (2020) “Flexural behaviour of NSM CFRP laminate strip systems in concrete using stiff and flexible adhesives” Composites Part B: Engineering, 195: 108042 1-18. DOI: https://doi.org/10.1016/j.compositesb.2020.108042 2. Cruz, J.R.; Sena-Cruz, J.; Rezazadeh, M.; Seręga, S.; Pereira, E.; Kwiecień, A.; Zając, B. (2020) “Bond behaviour of NSM CFRP laminate strip systems in concrete using stiff and flexible adhesives” Composite Structures, 250: 112369 1-18. DOI: https://doi.org/10.1016/j.compstruct.2020.112369 3. Correia, L.; Barris, C.; França, P.; Sena-Cruz, J. (2019) “Effect of Temperature on Bond Behavior of Externally Bonded FRP Laminates with Mechanical End Anchorage.” Journal of Composites for Construction, 23(5): 04019036-1 - 04019036-12. DOI: https://doi.org/10.1061/(ASCE)CC.1943-5614.0000961 4. Ribeiro, F.; Sena-Cruz, J.; Branco, F.; Júlio, E. (2019) “3D finite element model for hybrid FRP-confined concrete in compression using modified CDPM.” Engineering Structures, 190: 459–479. DOI: https://doi.org/10.1016/j.engstruct.2019.04.027 5. Soares, S.; Sena-Cruz, J.; Cruz, J.R.; Fernandes, P. (2019) “Influence of Surface Preparation Method on the Bond Behavior of Externally Bonded CFRP Reinforcements in Concrete.” Materials, 12(3) 414: 1–20. DOI: https://doi.org/10.3390/ma12030414 6. Ribeiro, F.; Sena-Cruz, J.; Branco, F.; Júlio, E. (2018) “Hybrid FRP jacketing for enhanced confinement of circular concrete columns in compression.” Construction & Building Materials, 184: 681–704. DOI: https://doi.org/10.1016/j.conbuildmat.2018.06.229 7. Barris, C.; Correia, L.; Sena-Cruz, J. (2018) “Experimental study on the bond behaviour of a transversely compressed mechanical anchorage system for externally bonded reinforcement.” Composite Structures, 200:871–890. DOI: https://doi.org/10.1016/j.compstruct.2018.05.084 8. Ribeiro, F.; Sena-Cruz, J.; Branco, F.G.; Júlio, E. (2018) “Hybrid effect and pseudo-ductile behaviour of unidirectional interlayer hybrid FRP composites for civil engineering applications.” Construction & Building Materials, 171:871–890. DOI: https://doi.org/10.1016/j.conbuildmat.2018.03.144 9. Coelho, M.; Neves, L.; Sena-Cruz, J. (2018) “Designing NSM FRP systems in concrete using partial safety factors.” Composites Part B: Engineering, 139:12-23. DOI: https://doi.org/10.1016/j.compositesb.2017.11.031 10. Fernandes, P.; Sena-Cruz, J.; Xavier, J.; Silva, P.; Pereira, E.; Cruz, J.R. (2018) “Durability of bond in NSM CFRP-concrete systems under different environmental conditions.” Composites Part B: Engineering, 138: 19–34. DOI: https://doi.org/j.compositesb.2017.11.022 17 Institute for Sustainability and Innovation in Structural Engineering 33Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Dissemination/Outputs Papers/Presentations in International Conferences: (12) Sena-Cruz, J.; Cruz, J.C.; Correia, L.; Cabral-Fonseca, S; Michels, J.; Czaderski, C. (2019) “Long-term structural and durability performances of reinforced concrete elements strengthened in flexure with CFRP laminates: a research project”, IABSE Symposium Guimarães 2019 - Towards a Resilient Built Environment Risk and Asset Management, March 27-29, Guimarães, 1006-1014 pp. URI: http://hdl.handle.net/1822/60198 Correia, L.; Sena-Cruz, J.; França, P. (2019) “Behaviour of RC structures strengthened with prestressed CFRP laminates: a numerical study”, IABSE Symposium Guimarães 2019 - Towards a Resilient Built Environment Risk and Asset Management, March 27-29, Guimarães, 276-283 pp. URI: http://hdl.handle.net/1822/60194 Cruz, J.R.; Sena-Cruz, J.; Borojevic, A.; Kwiecień, A.; Zając, B. (2018) “Influence of adhesive type on the flexural behaviour of RC slabs strengthened with NSM-CFRP systems”, 9th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE2018), July 17-19, Paris, 8 pp. URI: http://hdl.handle.net/1822/55647 Correia, L.; Barris, C.; Sena-Cruz, J. (2018) “Temperature effect on the bond behaviour of a transversely compressed mechanical anchorage system”, 9th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE2018), July 17-19, Paris, 8 pp. URI: http://hdl.handle.net/1822/55669 Sena-Cruz, J.; Correia, L.; Barris, C. (2018) “Behaviour of Metallic Anchorage Plates for Prestressing CFRP Laminates Under Room and Elevated Temperatures”, 40th IABSE Conference – Engineering the Developing World, April 25-27, Kuala Lumpur, 111-118. URI: http://hdl.handle.net/1822/55708 Sena-Cruz, J.; Correia, L.; França, P.; Michels, J.; (2017) “Short and long-term behaviour of RC slabs strengthened with prestressed CFRP laminate strips”, 39th IABSE Symposium – Engineering the Future, September 21-23, Vancouver, 8 pp. URI: http://hdl.handle.net/1822/50508 Sena-Cruz, J.; Michels, J.; Correia, L.; Harmanci, Y.; Silva, P.; Gallego, J.; Fernandes, P.; Czaderski, C.; França, P. (2017) “Recent contributions from UMinho and Empa on durability issues of flexural strengthening of RC slab with EB CFRP laminates”, 4th Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures (SMAR2017), September 13-15, Zurich, 8 pp. URI: http://hdl.handle.net/1822/50505 Soares, S.; Cruz, J.R.; Fernandes, P.; Sena-Cruz, J. (2017) “Bond behavior of EBR CFRP systems in concrete: influence of surface preparation”, 6th Asia-Pacific Conference on FRP in Structures (APFIS2017), 19 a 21 de julho, Singapura, 5 pp. URI: http://hdl.handle.net/1822/50502 Barris, C.; Correia, L.; Sena-Cruz, J. (2017) “Experimental study on the bond behaviour of a transversely compressed mechanical anchorage system for externally bonded reinforcement”, 6th Asia-Pacific Conference on FRP in Structures (APFIS2017), Singapore 19-21, Singapura, 4 pp. URI: http://hdl.handle.net/1822/50499 Sena-Cruz, J.; Fernandes, P.; Coelho, M.; Silva, P.; Granja, J.; Benedetti, A.; Azenha, M.; Neves, L. (2016) “Bond on NSM CFRP systems: recent contributions of UMinho on durability, quality control and design”, Eighth International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE2016), December 14-16, Hong Kong, 912-917 pp. URI: http://hdl.handle.net/1822/43901 Cruz, J.R.; Borojevic, A.; Sena-Cruz, J.; Pereira, E.; Fernandes, P.; Silva, P.; Kwiecien, A. (2016) “Bond behaviour of NSM CFRP-concrete systems: adhesive and CFRP cross-section influences”, Eighth International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE2016), December 14-16, Hong Kong, 930-935 pp. URI: http://hdl.handle.net/1822/43903 Silva, P.; Escusa, G.; Sena-Cruz, J.; Azenha, M. (2016) “Experimental investigation of RC slabs strengthened with NSM CFRP system subjected to elevated temperatures up to 80 C”, Eighth International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE2016), December 14-16, Hong Kong, 936-942 pp. URI: http://hdl.handle.net/1822/43902 Institute for Sustainability and Innovation in Structural Engineering 34 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Dissemination/Outputs Papers/Presentations in National Conferences: (10) Correia, L.; Sena-Cruz, J.; França, P. (2018) “Estudos numéricos de lajes de betão armado reforçadas à flexão com laminados de CFRP pré-esforçados.” Encontro Nacional Betão Estrutural - BE2018, 7 a 9 de novembro, Laboratório Nacional de Engenharia Civil, Lisboa, 10 pp. URI: http://hdl.handle.net/1822/58387 Ribeiro, F.; Sena-Cruz, J.; Branco, F.G.; Júlio, E. (2018) “Comportamento à compressão de pilares circulares de betão confinados por sistemas compósitos de FRP híbridos.” Encontro Nacional Betão Estrutural - BE2018, 7 a 9 de novembro, Laboratório Nacional de Engenharia Civil, Lisboa, 10 pp. URI: http://hdl.handle.net/1822/58385 Ribeiro, F.; Sena-Cruz, J.; Branco, F.G.; Júlio, E. (2018) “Comportamento à compressão de pilares circulares de betão confinados por sistemas compósitos de FRP híbridos.” Encontro Nacional Betão Estrutural - BE2018, 7 a 9 de novembro, Laboratório Nacional de Engenharia Civil, Lisboa, 10 pp. URI: http://hdl.handle.net/1822/58385 Coelho, M.; Caggiano, A.; Sena-Cruz, J.; Neves, L. (2016) “Lei Constitutiva para a Simulação da Ligação de Sistemas NSM FRP no Betão.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 10 pp. URI: http://hdl.handle.net/1822/43501 Fernandes, P.; Sena-Cruz, J.; Xavier, J.; Silva, P.; Soares, S. (2016) “Durabilidade da ligação entre o betão e laminados de CFRP aplicados de acordo com a técnica NSM.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 8 pp. URI: http://hdl.handle.net/1822/43549 Correia, L.; Sena-Cruz, J.; França, P.; Michels, J.; Pereira, E.; Escusa, G. (2016) “Efeito de distintas condições ambientes na durabilidade de lajes de betão armado reforçadas com laminados de CFRP préesforçados.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 10 pp. URI: http://hdl.handle.net/1822/43506 Coelho, M.; Sena-Cruz, J.; Neves, L. (2016) “Coeficientes parciais de segurança para o dimensionamento da ligação de sistemas NSM FRP no betão.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 9 pp. URI: http://hdl.handle.net/1822/43493 Silva, P.; Escusa, G.; Sena-Cruz, J.; Azenha, M. (2016) “Investigação experimental de lajes reforçadas com sistemas NSM CFRP submetidas a temperaturas até 80 °C.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 8 pp. URI: http://hdl.handle.net/1822/43548 Cruz, R.; Borojevic, A.; Sena-Cruz, J.; Pereira, E.; Fernandes, P.; Silva, P.; Kwiecien, A. (2016) “Comportamento da aderência de sistema de reforço NSM-CFRP na presença de diferentes tipos de adesivos.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 9 pp. URI: http://hdl.handle.net/1822/43511 Cruz, R.; Borojevic, A.; Sena-Cruz, J.; Silva, P.; Fernandes, P.; Kwiecien, A. (2016) “Influência do tipo de adesivo no comportamento à flexão de faixas de laje reforçadas com sistemas NSM-CFRP.” Encontro Nacional Betão Estrutural - BE2016, 2 a 4 de novembro, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Coimbra, 10 pp. URI: http://hdl.handle.net/1822/43541 18 Acknowledgments Institute for Sustainability and Innovation in Structural Engineering 36 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Acknowledgments > Companies 19 Institute for Sustainability and Innovation in Structural Engineering 37Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | This work was supported by FEDER funds through the Operational Program for Competitiveness Factors – COMPETE and National Funds through FCT (Portuguese Foundation for Science and Technology) under the project FRPLongDur POCI-01-0145-FEDER-016900 and partly financed by the project POCI-01-0145-FEDER 007633SFRH/BD/80682/2011. Acknowledgments > Funding agencies/programs Institute for Sustainability and Innovation in Structural Engineering 38 Project FRPLongDur: Motivation, objectives, execution J. Sena-Cruz | Many Thanks/Muito obrigado! 20 Durability of materials Susana Cabral-Fonseca LNEC | 13 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T0 @ Concrete T0: Initial characterisation T1 & T2: one and two years of ageing in different experimental stations LNEC | 14 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T0 @ Concrete Compressive properties of concrete (28 days) Compressive strength [MPa] (CoV [%]) Modulus of elasticity [GPa] (CoV [%]) 41.5 (4.4) 29.1 (4.7) 28 LNEC | 15 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T0 @ Concrete Tensile strength, by Pull-off [MPa] (CoV [%]) 3.4 (13.3) LNEC | 16 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations 29 LNEC | 17 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations Compressive properties LNEC | 18 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete 30 LNEC | 19 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete LNEC | 20 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 4.9 + 8.2 + 8.4 + 4.9 + 10.0 T2 - 10.9 + 6.2 + 16.2 + 11.3 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 + 0.7 + 5.0 + 2.1 + 2.1 + 7.9 T2 - 3.5 - 5.9 + 3.5 + 1.4 Variation (%) 31 LNEC | 21 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 4.9 + 8.2 + 8.4 + 4.9 + 10.0 T2 - 10.9 + 6.2 + 16.2 + 11.3 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 + 0.7 + 5.0 + 2.1 + 2.1 + 7.9 T2 - 3.5 - 5.9 + 3.5 + 1.4 Variation (%)   Retention 1.21 0.93 Retention 0.93 1.04 LNEC | 22 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations Tensile properties 32 LNEC | 23 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete LNEC | 24 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete 33 LNEC | 25 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 13.1 + 10.0 + 11.2 + 8.1 - 7.9 T2 - 26.3 - 11.8 - 4.3 - 3.2 Variation (%) LNEC | 26 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 13.1 + 10.0 + 11.2 + 8.1 - 7.9 T2 - 26.3 - 11.8 - 4.3 - 3.2 Variation (%)  Retention 0.96 0.70 34 LNEC | 27 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations Deep of carbonation LNEC | 28 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete 35 LNEC | 29 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 2.7 + 37.4 + 6.7 + 6.0 + 8.7 T2 - 28.0 + 20.6 + 9.4 + 4.3 Variation (%) LNEC | 30 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Concrete E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 2.7 + 37.4 + 6.7 + 6.0 + 8.7 T2 - 28.0 + 20.6 + 9.4 + 4.3 Variation (%) 36 LNEC | 31 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T0 @ Adhesives T0: Initial characterisation T1 & T2: one and two years of ageing in different experimental stations LNEC | 32 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Chemical composition 459,19 610,26 636,19 693,83 778,40 796,86 828,10 1083,48 1181,26 1362,35 1459,10 1509,87 1608,12 2870,19 2925,50 2963,61 3405,57 -0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 Absorbance 500 1000 1500 2000 2500 3000 3500 Wavenumbers (cm-1) 460,92 510,16 692,19 779,50 795,43 876,23 1083,50 1175,83 1454,56 1510,36 1610,24 1795,93 1877,94 2869,37 2926,21 2959,25 3425,76 -0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 Absorbance 500 1000 1500 2000 2500 3000 3500 Wavenumbers (cm-1) Epoxy based resins with silica fillers 28 days of cure at 23 ºC ADH1 ADH2 T0 @ Adhesives 37 LNEC | 45 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives ADH1 ADH2 Tg  with time [outdoor] LNEC | 46 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives ADH1 ADH2 Tg  with time [immersion in water] 44 LNEC | 47 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 7.5 + 2.9 + 2.2 + 1.6 - 0.9 T2 - 14.6 + 7.0 + 8.7 + 11.3 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 6.2 + 0.4 - 1.3 - 2.1 + 0.7 T2 - 16.3 + 1.0 + 2.9 + 6.6 Variation (%) Retention Retention 0.94 1.22 0.96 1.22 LNEC | 48 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations TENSILE PROPERTIES 45 LNEC | 49 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives LNEC | 50 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 62.8 + 1.9 + 3.3 + 12.5 - 9.0 T2 - 63.5 - 4.5 - 5.6 - 1.5 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 71.9 + 2.0 + 9.2 + 13.8 - 6.7 T2 - 73.3 - 1.7 - 10.6 + 0.7 Variation (%) 46 LNEC | 51 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 62.8 + 1.9 + 3.3 + 12.5 - 9.0 T2 - 63,5 - 4.5 - 5.6 - 1.5 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 71.9 + 2.0 + 9.2 + 13.8 - 6.7 T2 - 73.3 - 1.7 - 10.6 + 0.7 Variation (%)     Retention Retention 0.33 1.09 0.25 1.16 LNEC | 52 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 52.3 + 13.0 + 8.1 + 12.1 + 16.5 T2 - 58.2 + 5.6 - 2.1 + 9.0 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 60.5 + 10.0 + 5.5 + 8.3 + 22.6 T2 - 63.2 + 4.7 - 2.8 + 7.3 Variation (%) 47 LNEC | 53 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ Adhesives E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 52.3 + 13.0 + 8.1 + 12.1 + 16.5 T2 - 58.2 + 5.6 - 2.1 + 9.0 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 60.5 + 10.0 + 5.5 + 8.3 + 22.6 T2 - 63.2 + 4.7 - 2.8 + 7.3 Variation (%)      Retention 0.44 1.36 0.39 1.48 Retention LNEC | 54 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T0 @ CFRP T0: Initial characterisation T1 & T2: one and two years of ageing in different experimental stations 48 LNEC | 55 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions CFRP Tensile properties Tensile strength [MPa] (CoV [%]) Modulus of elasticity [GPa] (CoV [%]) Strain at break [×10-3] (CoV [%]) L10 2.40 x 103(3.9) 164 (1.2) 15 (4) L50 2.53 x 103(10.1) 190 (9.3) 13 (14) T0 @ CFRP LNEC | 56 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ CFRP T0: initial characterisation T1 & T2: one and two years of ageing in different experimental stations 49 LNEC | 57 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ CFRP LNEC | 58 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ CFRP E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 + 0.5 + 4.4 + 3.1 - 2.3 - 0.2 T2 + 3.4 + 2.5 + 3.5 + 3.6 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 - 3.1 - 1.3 - 2.4 - 3.2 - 4.7 T2 - 1,0 + 4,1 + 5.5 + 6.7 Variation (%) Retention Retention 1.05 1.16 1.01 1.09 50 LNEC | 59 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions T1 & T2 @ CFRP E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 + 0.1 + 1.1 + 0.4 - 1.0 - 3.0 T2 + 3.9 + 9.5 + 8.2 + 4.8 Variation (%) E2/E1 E3/E1 E4/E1 E5/E1 E6/E1 T1 + 1.8 + 0.2 + 1.4 + 2.5 - 2.6 T2 + 3.3 + 7.0 + 7.0 + 7.0 Variation (%) Retention 0.99 1.10 0.86 0.94 LNEC | 60 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Initial characterization > Concrete Compressive strength: 41.5 MPa Modulus of elasticity: 29.1 GPa Tensile strength, by Pull-off: 3.4 MPa 51 LNEC | 61 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Initial characterization > Adhesives ADH1 ADH2 Composition Epoxy based resins with silica fillers Water absorption 20 ºC +++ (5%) + (1%) 40 ºC +++ (5%) + (2%) 60 ºC +++ (5%) + (5%) Tg (ºC) E’ onset 46.2 44.3 Tan 57.0 55.3 Tensile properties Tensile strength (MPa) 19.9 24.8 Modulus of elasticity (GPa) 6.50 7.99 Strain at break (%) 4.0 4.5 LNEC | 62 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Initial characterization > CFRP laminates Tensile strength (GPa): 2.40 – 2.53 Tensile modulus (GPa): 164 – 190 52 LNEC | 63 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Durability > Concrete Ei @ E1: • Compressive strength immersion in water [E2] outdoor [E3, E4, E5, E6] • Tensile strength (pull-off) [E2,E3,E4,E5,E6] Retention (@ 28 days): • Compressive strength: Min: [E2@T2] = 0.93 Max: [E4@T2] = 1.21 • Compressive modulus of elasticity: Min: [E3@T2] = 0.93 Max: [E6@T1] = 1.04 • Tensile strength: Min: [E3@T2] = 0.93 Max: [E6@T1] = 1.04 LNEC | 64 1. Introduction 2. Materials 3. Methods 4. Results 5. Conclusions Durability > Adhesives > Glass Transition Temperature Ei @ E1: For both adhesives: • Tg immersion in water [E2] outdoor [E3, E4, E5, E6] Retention (@ 28 days): ADH1 Min: [E2@T2] = 0.94 Max: [E5@T2] = 1.22 ADH2 Min: [E2@T2] = 0.96 Max: [E5@T2] = 1.22 53 Institute for Sustainability and Innovation in Structural Engineering 3Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Introduction/Motivation/Objectives Objective: to evaluate de durability of bond between CFRP laminates and concrete under real outdoor conditions by comparing with reference environments. Materials (Concrete, epoxy, and CFRP) Bond Specimens (EBR and NSM) Exposure to outdoor environmental actions E1: Reference (indoor) E2: Immersion in water E3: Outdoor - carbonatation E4: Outdoor - freeze-thaw attack E5: Outdoor - elevated temperatures E6: Outdoor - chloride exposure Comparison with accelerated ageing studies performed in laboratory Numerical and Analytical Simulations Design Recommendations Slabs under sustained load (EBR and NSM) Institute for Sustainability and Innovation in Structural Engineering 4Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Main objective: to determine along the time and depending on the type of environment of exposure condition, mainly, the evolution of specimen’s stiffness,bond strength and failure modes. Main steps: •Specimens production • Casting • EBR sand blasting / NSM groove’s opening • Strengthening • Storage before installation •T0 tests •Installation •Visits to Experimental Stations •T1 Collecting – T1 Tests •Visits to Experimental Stations •T2 Collecting – T2 Tests T0 T1 T2 After the production of the specimens to determine it’s initial mechanical properties After 1 (T1) and 2 (T2) years of exposure to the environments (E1 – E6) 60 Institute for Sustainability and Innovation in Structural Engineering 5Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Specimen’s production Casting EBR – Sandblasting NSM – Groove’s opening CFRP placement EBR NSM Storage inside the laboratory until the installation Institute for Sustainability and Innovation in Structural Engineering 6 Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Installation Reference environments E1@UMinho E2@UMinho 20 °C / 55% RH Immersion in water at 20 °C 61 Institute for Sustainability and Innovation in Structural Engineering 7Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Installation Real outdoor environments Orientation of exposure: Sunrise-sunset E3@LNEC in Lisbon E6@Viana do Castelo E4@Serra da Estrela E5@Elvas Specimens placed together side by side to avoid the risk of tipping Placement of a grid between the specimens and the ground Institute for Sustainability and Innovation in Structural Engineering 8Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Collecting and storage before test – T1 and T2 Collecting E3-E6 Storage during two weeks for humidity control E3-E6 Test immediately after removing from water E2 62 Institute for Sustainability and Innovation in Structural Engineering 9Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Experimental program Properties to be evaluated: •Force versus slip •Maximum Force (Fmax) •Slip at Fmax •Bond strength τmax •Local bond slip law τ – s •Failure modes EBR Concrete prism: 200×200×400 mm3 CFRP laminate: 50×1.2 mm2 Bond length: 220 mm Specimen geometry and test configuration Institute for Sustainability and Innovation in Structural Engineering 10Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | NSM Concrete cube: 200×200×200 mm3 CFRP laminate: 10×1.4 mm2 Bond length: 60 mm Experimental program Properties to evaluate: •Force versus slip •Maximum Force (Fmax) •Slip at Fmax •Bond strength τmax •Local bond slip law τ – s •Failure modes Specimen geometry and test configuration 63 Institute for Sustainability and Innovation in Structural Engineering 11Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | 0.0 0.2 0.4 0.6 0.8 0 10 20 30 40 Force, F [kN] Loaded end slip, sl [mm] BT_EBR_T0_1 BT_EBR_T0_2 BT_EBR_T0_3 BT_EBR_T0_4 Results at T0 Curves pullout force versus slip EBR NSM Fmax = 28.4 kN 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 10 20 30 40 Force, F [kN] Loaded end slip, sl [mm] BT_NSM_T0_1 BT_NSM_T0_2 BT_NSM_T0_3 BT_NSM_T0_4 Fmax = 28.2 kN T0 Institute for Sustainability and Innovation in Structural Engineering 12 Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | E1 E2 E3 E4 E5 E6 0 10 20 30 40 Maximum force [KN] Environment T0 Average 28.4 kN Results during the time EBR - Fmax T1 Maximum force Variation of Fmax in relation to E1 -0.8 14.5 5.1 4.1 6.7 E2 E3 E4 E5 E6 -30 -20 -10 0 10 20 30 Strength variation [%] Environment Fmax increased in relation to E1, specially in E3 64 Institute for Sustainability and Innovation in Structural Engineering 13Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | E1 E2 E3 E4 E5 E6 0 10 20 30 40 Maximum force [KN] Environment T0 Average 28.4 kN Results during the time EBR - Fmax T2 15.9 25.9 26.1 7 E2 E3 E4 E5 E6 -30 -20 -10 0 10 20 30 Strength variation [%] Environment .0 Fmax increased in relation to E1 in environments, mainly in E3 and E4 Maximum force Variation of Fmax in relation to E1 Institute for Sustainability and Innovation in Structural Engineering 14Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Results during the time E1 E2 E3 E4 E5 E6 0 5 10 15 20 25 30 35 40 Maximum force [KN] T1 T2 T0 0.1 17 10.1 20 2.8 E1 E2 E3 E4 E5 E6 -25 -20 -15 -10 -5 0 5 10 15 20 25 .0 Environment T1-T2 Fmax variation T1-T2 [%] .0 •In E1, the Fmax is similar in T1 and T2 •Fmax increased in all environments mainly in E2 and E4 T1 T2 EBR - Fmax Maximum force Variation of Fmax from T1 to T2 65 Institute for Sustainability and Innovation in Structural Engineering 15Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Results during the time EBR – Failure modes in each environment E1 – E6 C Cohesive failure of concrete T1 T2 Institute for Sustainability and Innovation in Structural Engineering 16 Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | -12.6 -3.7 -3.8 3 6 E2 E3 E4 E5 E6 -15 -10 -5 0 5 10 15 .0 Strength variation [%] Environment .0 E1 E2 E3 E4 E5 E6 0 10 20 30 40 Maximum force [KN] Environment T0 Average 28.2 kN Results during the time NSM - Fmax •Fmax reduced in E2 (mainly), E3 and E4 •Fmax slightly increased in E5 and in E6 T1 Maximum force Variation of Fmax in relation to E1 66 Institute for Sustainability and Innovation in Structural Engineering 17Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | -12.2 -3.8 -8.4 0.3 E2 E3 E4 E5 E6 -15 -10 -5 0 5 10 15 Strength variation [%] Environment E1 E2 E3 E4 E5 E6 0 10 20 30 40 Maximum force [KN] Environment T0 Average 28.2 kN Results during the time NSM - Fmax •Fmax reduced E2 (mainly), E3 and E4 •In E5, Fmax is similar to E1 T2 Maximum force Variation of Fmax in relation to E1 Institute for Sustainability and Innovation in Structural Engineering 18Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | -2.7 -2.3 -2.8 -7.3 -5.3 E1 E2 E3 E4 E5 E6 -15 -10 -5 0 5 10 15 Environment T1-T2 Fmax variation T1-T2 [%] E1 E2 E3 E4 E5 E6 0 5 10 15 20 25 30 35 40 Maximum force [KN] T1 T2 T0 Results during the time NSM - Fmax •A slightly decrease of Fmax was observed in E1, E2 and E3 environments and a higher reduction was observed in E4 and in E5 T1 T2 Maximum force Variation of Fmax from T1 to T2 67 Institute for Sustainability and Innovation in Structural Engineering 19Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Results during the time NSM – Failure modes in each environment E1 E3 I-FA Debonding at CFRPAdhesive interface E4 I-FA + CC Debonding at CFRPAdhesive interface with concrete cracking E5 I-FA + CS Debonding at CFRPAdhesive interface with concrete splitting T1 T2 Institute for Sustainability and Innovation in Structural Engineering 20Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Results during the time NSM – Failure modes in each environment E2 I-AC + CS Debonding at AdhesiveConcrete interface with concrete splitting I-FA + C-C + CS Debonding at CFRPAdhesive interface and cohesive failure of concrete with concrete splitting C-A + CS Cohesive failure of adhesive with concrete splitting T1 T2 68 Institute for Sustainability and Innovation in Structural Engineering 21Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Environmental retention factors Retention factors based on de evolution of Fmax from T0 to T1 and T2 Environment RF_T1 RF_T2 E1 0.90 0.90 E2 0.90 1.05 E3 1.04 1.14 E4 0.95 1.14 E5 0.94 0.97 E6 0.96 - EBR Environment RF_T1 RF_T2 E1 1.02 0.99 E2 0.89 0.87 E3 0.98 0.96 E4 0.98 0.91 E5 1.05 1.00 E6 1.08 NSM Institute for Sustainability and Innovation in Structural Engineering 22Durability of bond with EBR and NSM strengthening techniques Ricardo Cruz | Conclusions From T0 to T1, Fmax decreased in EBR technique and remains almost constant in the case of NSM technique. The bond strength tends to slightly increase in the case of EBR technique with the environmental exposure conditions, while in the case of NSM technique, the bond strength tends to decrease. The water immersion affects more the NSM specimens than EBR specimens. The dominant failure mode in EBR technique remained the same regardless the type of environmental exposure condition. The several failure modes characterize the NSM technique, being the debonding at CFRP/adhesive dominant failure. Up to 2 years of exposure, retention factors of strength still remain higher than ~0.9. 69 Institute for Sustainability and Innovation in Structural Engineering 7Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Specimens definition > Reinforced Concrete Slabs Geometry Real scale Concrete fcm = 41.5 MPa (@ time T0) Ecm = 29.1 GPa (@ time T0) Steel ( ∅𝟖/∅𝟔) fy= (528 / 581) MPa (@ time T0) ft= (687 / 698) MPa (@ time T0) Es= (241 / 228) GPa (@ time T0) 3f6 5f8 Institute for Sustainability and Innovation in Structural Engineering 8 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Specimens definition > Reinforced Concrete Slabs Ultimate Load ≈30 kN Double the Ultimate Load ≈60 kN CUT PLANE 600 120 20 5?8 3?6 [email protected] m f6@ 300 mm 3f6 5f8 600 mm 120 mm 20 mm Cross Section 76 Institute for Sustainability and Innovation in Structural Engineering 9Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Cross Section Cross Section Cross Section Cross Section Specimens definition > Reinforced Concrete Slabs Non-prestressed NSM Solution Non-prestressed EBR Solution Prestressed EBR Solution (MA System) Prestressed EBR Solution (GA System) Cross Section 120 75 150 75150150 CFRP Non-prestressed NSM Solution CFRP (𝟏𝟎 × 𝟏.𝟒 [𝒎𝒎]) Cross Section 120 300 300 CFRP Non-prestressed EBR Solution CFRP (𝟏𝟎𝟎 × 𝟏. 𝟐 [𝒎𝒎]) Cross Section 120 300 300 CFRP Prestressed EBR Solution (MA System) CFRP (5𝟎 × 𝟏.𝟐 [𝒎𝒎]) (𝛆𝒇,𝒑 = 𝟎. 𝟒%) Cross Section 120 300 300 CFRP Prestressed EBR Solution (GA System) CFRP (5𝟎 × 𝟏.𝟐 [𝒎𝒎]) (𝛆𝒇,𝒑 = 𝟎. 𝟒%) Institute for Sustainability and Innovation in Structural Engineering 10 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Specimens definition > Reinforced Concrete Slabs CFRP (𝟏𝟎 × 𝟏.𝟒 [𝒎𝒎]) ff= 2005 MPa (@ time T0) Ef= 164 GPa (@ time T0) (𝟏𝟎𝟎 × 𝟏. 𝟐 [𝒎𝒎]) ff= 2620 MPa (@ time T0) Ef= 188 GPa (@ time T0) (𝟓𝟎 × 𝟏.𝟐 [𝒎𝒎]) ff= 2526 MPa (@ time T0) Ef= 190 GPa (@ time T0) 77 Experimental Program Institute for Sustainability and Innovation in Structural Engineering 12 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Experimental Program > Short and Long-term study T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 START 10 years (time) NSM MA GAEBRREF Short-term Flexural tests up to failure NSM MA GAEBR6 × Long-term Creep tests in 6 different environments 78 Institute for Sustainability and Innovation in Structural Engineering 13Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 100450450300 2600 CFRP LVDT LVDT CENTRELINE F/2 SG 100 450 450 300 F/2 LVDTLVDT LVDT NSM MA GAEBRREF Short-term Flexural tests up to failure Experimental Program > Short-term study (test set-up) Institute for Sustainability and Innovation in Structural Engineering 14 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Experimental Program > Short-term study (test set-up) NSM MA GAEBRREF Short-term Flexural tests up to failure 79 Institute for Sustainability and Innovation in Structural Engineering 15Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Experimental Program > Long-term study (test set-up) Long-term Creep tests in 6 different environments NSM MA GAEBR6 × 100900300 2600 CFRP 100 900 300 CREEP LOAD MECHANICAL DIAL Institute for Sustainability and Innovation in Structural Engineering 16 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Experimental Program > Long-term study (test set-up) Long-term Creep tests in 6 different environments NSM MA GAEBR6 × 80 Institute for Sustainability and Innovation in Structural Engineering 17Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Experimental Program > Long-term study (test set-up) Long-term Creep tests in 6 different environments NSM MA GAEBR6 × NSM MA GAEBR NSM MA GAEBRE2 NSM MA GAEBRE3 NSM MA GAEBRE4 NSM MA GAEBRE5 NSM MA GAEBRE6 E1 Lab. (20ºC & 55% RH) E1 Lab. (20ºC & 100% RH)E2 E2 Outdoor (Lisbon)E3 E3 Outdoor (Serra da Estrela)E4 E4 Outdoor (Elvas)E5 E5 Outdoor (Viana do Castelo)E6 E6 Short-term study 81 NSM MA GAEBRREF Flexural tests up to failure Institute for Sustainability and Innovation in Structural Engineering 20 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Short-term study > Force / Mid-span displacement 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 Mid-span displacement, d[mm] Force, F [kN] REF LEGEND KI KII C Y Steel Yielding Concrete Cracking F Failure KIII (Concrete cracking) 82 Institute for Sustainability and Innovation in Structural Engineering 21Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 Short-term study > Force / Mid-span displacement Mid-span displacement, d[mm] Force, F [kN] REF LEGEND C Y Steel Yielding Concrete Cracking F Failure Y F C NSM NSM CFRP ruptureF Higher loadY Similar LoadC Institute for Sustainability and Innovation in Structural Engineering 22 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 Short-term study > Force / Mid-span displacement Mid-span displacement, d[mm] Force, F [kN] REF LEGEND C YF Y F C NSM EBR CFRP debondingF Higher loadY Similar LoadC NSM CFRP ruptureF Higher loadY Similar LoadC EBR 83 Institute for Sustainability and Innovation in Structural Engineering 23Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 Short-term study > Force / Mid-span displacement Mid-span displacement, d[mm] Force, F [kN] REF LEGEND C YF Y F C NSM EBR CFRP debondingF Higher loadY Similar LoadC NSM CFRP ruptureF Higher loadY Similar LoadC MA CFRP ruptureF Higher loadY Higher LoadC CFRP DebondingD EBR MA Institute for Sustainability and Innovation in Structural Engineering 24 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 Short-term study > Force / Mid-span displacement Mid-span displacement, d[mm] Force, F [kN] REF LEGEND C YF Y F C NSM EBR CFRP debondingF Higher loadY Similar LoadC NSM CFRP ruptureF Higher loadY Similar LoadC MA CFRP ruptureF Higher loadY Higher LoadC EBR MA GA GA GA GA 84 Institute for Sustainability and Innovation in Structural Engineering 25Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | 0.0 0.1 0.2 0.3 0.4 0 10 20 30 40 50 60 70 80 0.0 0.4 0.8 1.2 1.6 2.0 0 10 20 30 40 50 60 70 80 Short-term study > Force / Mid-span Strain NSM EBR MA GA Mid-span CFRP strain, ef[%] Force, F [kN] NSM EBR MA GA Mid-span Concrete strain variation, Dec[%] REF LEGEND LEGEND 16.2% 14.1% D DD CFRP Debonding 0.4% Institute for Sustainability and Innovation in Structural Engineering 26 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Short-term study > Numeric Simulations (Model geometry and Mesh) Support Load Point Concrete Longitudinal Reinforcement Transverse Reinforcement Mid-span 30 120 30 50 200 300 300100 30050 Slabs were simulated as a plane state problem Different FE meshes were used Slab: REF 85 Institute for Sustainability and Innovation in Structural Engineering 39Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 Institute for Sustainability and Innovation in Structural Engineering 40 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 92 Institute for Sustainability and Innovation in Structural Engineering 41Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 Institute for Sustainability and Innovation in Structural Engineering 42 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 93 Institute for Sustainability and Innovation in Structural Engineering 43Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC1 0 f10 del d10 dC1 0 f10 del d10 dC1 0 f10 del d10 dC1 0 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 Institute for Sustainability and Innovation in Structural Engineering 44 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC1 0 f10 del d10 dC1 0 f10 del d10 dC1 0 f10 del d10 dC1 0 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 ≈ ≈ 94 Institute for Sustainability and Innovation in Structural Engineering 45Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 8.32 12.8 4.51 0.54 11.3 18.0 6.67 0.60 4.78 10.0 5.25 1.10 5.09 9.20 4.11 0.81 E3 8.42 16.2 7.79 0.93 11.0 20.2 9.16 0.83 4.78 11.8 7.06 1.48 4.58 12.0 7.39 1.61 E4 8.54 16.0 7.44 0.87 12.1 20.7 8.55 0.71 5.11 12.7 7.06 1.49 5.33 12.8 4.46 1.40 E5 7.89 15.1 7.17 0.91 12.1 21.8 9.67 0.80 5.65 13.3 7.68 1.36 4.83 12.2 7.35 1.52 E6 8.50 14.6 6.08 0.72 10.4 18.4 8.01 0.77 5.13 11.3 6.17 1.26 3.41 10.4 7.01 2.06 Institute for Sustainability and Innovation in Structural Engineering 46 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 ↓ -31% 0.54 ↓ -20% 0.60 ↑ 6% 1.10 ↓ -33% 0.81 E3 ↑ 19% 0.93 ↑ 11% 0.83 ↑ 42% 1.48 ↑ 34% 1.61 E4 ↑ 12 0.87 ↓ -5% 0.71 ↑ 43% 1.49 ↑ 17% 1.40 E5 ↑ 17 0.91 ↑ 7% 0.80 ↑ 31% 1.36 ↑ 27% 1.52 E6 ↓ -8% 0.72 ↑ 3% 0.77 ↑ 21% 1.26 ↑ 72% 2.06 95 Institute for Sustainability and Innovation in Structural Engineering 47Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Long-term study > Main Results EBR NSM MA GA del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 del d10 dC10 f10 [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] [mm] [mm] [mm] [-] E1 7.33 13.1 5.74 0.78 10.3 18.1 7.78 0.75 4.67 9.54 4.87 1.04 4.44 9.77 5.33 1.20 E2 ↓ -31% 0.54 ↓ -20% 0.60 ↑ 6% 1.10 ↓ -33% 0.81 E3 ↑ 19% 0.93 ↑ 11% 0.83 ↑ 42% 1.48 ↑ 34% 1.61 E4 ↑ 12 0.87 ↓ -5% 0.71 ↑ 43% 1.49 ↑ 17% 1.40 E5 ↑ 17 0.91 ↑ 7% 0.80 ↑ 31% 1.36 ↑ 27% 1.52 E6 ↓ -8% 0.72 ↑ 3% 0.77 ↑ 21% 1.26 ↑ 72% 2.06 Conclusions 96 Institute for Sustainability and Innovation in Structural Engineering 49Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Conclusions Short-term study All the four strengthening solutions led to higher ultimate load. From the non-prestressed solutions, the NSM technique allowed the strengthening goal (double the ultimate load) with the lowest amount of CFRP. Similar response was observed in both anchorage techniques. Yet, the metallic anchors composing the MA system prevented a premature failure. Prestress allowed a more efficient use of the materials: (i) achied the strengthening goal with lower amount of CFRP; and (ii) higher CFRP strains at failure. Short-term study All the four strengthening solutions led to higher ultimate load. From the non-prestressed solutions, the NSM technique allowed the strengthening goal (double the ultimate load) with the lowest amount of CFRP. Similar response was observed in both anchorage techniques. Yet, the metallic anchors composing the MA system prevented a premature failure. Prestress allowed a more efficient use of the materials: (i) achied the strengthening goal with lower amount of CFRP; and (ii) higher CFRP strains at failure. Institute for Sustainability and Innovation in Structural Engineering 50 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Conclusions Long-term study Instantaneous mid-span displacement after the placement of the gravity load is similar to values registered in the short-term flexural tests up to failure. Good correlation between the test results from the FRPlondDur project and previous results. Laboratory environments lead to the lowest creep developments, regardless of the strengthening solution. Specimens exposed to the outdoor environments show higher creep developments, and higher creep coefficients: Average creep coefficient in outdoor environments after 10 000h : 0.78, 0.86, 1.40, and 1.65 for NSM, EBR, MA and GA, respectively. Long-term study Instantaneous mid-span displacement after the placement of the gravity load is similar to values registered in the short-term flexural tests up to failure. Good correlation between the test results from the FRPlondDur project and previous results. Laboratory environments lead to the lowest creep developments, regardless of the strengthening solution. Specimens exposed to the outdoor environments show higher creep developments, and higher creep coefficients: Average creep coefficient in outdoor environments after 10 000h : 0.78, 0.86, 1.40, and 1.65 for NSM, EBR, MA and GA, respectively. 97 Acknowledgments Institute for Sustainability and Innovation in Structural Engineering 52 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Acknowledgments > Companies 98 Institute for Sustainability and Innovation in Structural Engineering 53Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | This work was supported by FEDER funds through the Operational Program for Competitiveness Factors – COMPETE and National Funds through FCT (Portuguese Foundation for Science and Technology) under the project FRPLongDur POCI-01-0145-FEDER-016900 and partly financed by the project POCI-01-0145-FEDER 007633SFRH/BD/80682/2011. Acknowledgments > Funding agencies/programs Institute for Sustainability and Innovation in Structural Engineering 54 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Institute for Sustainability and Innovation in Structural Engineering 54 Durability and long-term behaviour of slabs strengthened according to EBR and NSM techniques L. Correia | Use mask! I’m not using because I’m very young. 99