TY - JOUR

T1 - Development of prestressed unbonded and bonded CFRP strengthening solutions for tensile metallic members

AU - Hosseini, Ardalan

AU - Ghafoori, Elyas

AU - Motavalli, Masoud

AU - Nussbaumer, Alain

AU - Zhao, Xiao Ling

AU - Al-Mahaidi, Riadh

AU - Terrasi, Giovanni

N1 - Funding Information: This paper is an extended version of the authors’ paper presented in SMAR 2017 conference, 13–15 September 2017, ETH Zurich, Switzerland. The authors gratefully acknowledge the financial support provided by the Swiss National Science Foundation (SNSF Project No. 200021–153609) and the Australian Research Council (ARC) Linkage Grant ( LP140100543 ). The authors would like to thank the technicians of the Structural Engineering Research Laboratory, Mechanical Systems Engineering Laboratory, and the Central Workshop of Empa for their exceptional cooperation in manufacturing the mechanical parts and performing the experiments. Special thanks also go to Robin Pauer at the Electron Microscopy Center of Empa for his kind assistance with scanning electron microscopy. Finally, the support of S&P Clever Reinforcement Company AG, Switzerland, who provided the materials for the current study, is acknowledged. Publisher Copyright: © 2018 Elsevier Ltd

PY - 2019/2/15

Y1 - 2019/2/15

N2 - In this study, a novel unbonded mechanical clamping system was developed for the strengthening of tensile metallic members using prestressed carbon fiber reinforced polymer (CFRP) plates. The system clamps a pair of prestressed CFRP reinforcement to a metallic substrate and provides an almost uniform contact pressure over the CFRP plate along the anchorage length. A finite element simulation was used to optimize the design of the mechanical components of the system. Subsequently, a set of static and fatigue tests was performed to evaluate the performance of the optimized design. Experimental results revealed that the proposed mechanical clamping system is capable of transferring the entire tensile capacity of the CFRP plates to the steel substrate, even after experiencing 10 million fatigue cycles. The comparative performance of the developed clamps was further investigated by a set of static tests on steel plate specimens strengthened with the prestressed bonded reinforcement (PBR) and the newly developed prestressed unbonded reinforcement (PUR) systems. Furthermore, simple analytical models are proposed to formulate the stress state in prestressed unbonded and bonded CFRP-strengthened tensile metallic members. The accuracy of the proposed analytical formulations was verified by the experimental results obtained during the current study. Experimental results revealed that the efficacy of having relatively high prestressing forces in the normal modulus (NM) CFRP reinforcements is much higher than the stiffness improvement obtained by using ultra-high modulus (UHM) CFRPs. However, the available capacity of the PBR system before debonding failure is far lower than that of the developed PUR solution.

AB - In this study, a novel unbonded mechanical clamping system was developed for the strengthening of tensile metallic members using prestressed carbon fiber reinforced polymer (CFRP) plates. The system clamps a pair of prestressed CFRP reinforcement to a metallic substrate and provides an almost uniform contact pressure over the CFRP plate along the anchorage length. A finite element simulation was used to optimize the design of the mechanical components of the system. Subsequently, a set of static and fatigue tests was performed to evaluate the performance of the optimized design. Experimental results revealed that the proposed mechanical clamping system is capable of transferring the entire tensile capacity of the CFRP plates to the steel substrate, even after experiencing 10 million fatigue cycles. The comparative performance of the developed clamps was further investigated by a set of static tests on steel plate specimens strengthened with the prestressed bonded reinforcement (PBR) and the newly developed prestressed unbonded reinforcement (PUR) systems. Furthermore, simple analytical models are proposed to formulate the stress state in prestressed unbonded and bonded CFRP-strengthened tensile metallic members. The accuracy of the proposed analytical formulations was verified by the experimental results obtained during the current study. Experimental results revealed that the efficacy of having relatively high prestressing forces in the normal modulus (NM) CFRP reinforcements is much higher than the stiffness improvement obtained by using ultra-high modulus (UHM) CFRPs. However, the available capacity of the PBR system before debonding failure is far lower than that of the developed PUR solution.

KW - Analytical solution

KW - Carbon fiber reinforced polymer (CFRP)

KW - Fatigue strengthening

KW - Prestressed bonded reinforcement (PBR)

KW - Prestressed unbonded reinforcement (PUR)

KW - Steel structure

KW - Ultra-high modulus (UHM) CFRP

UR - http://www.scopus.com/inward/record.url?scp=85058806534&partnerID=8YFLogxK

U2 - 10.1016/j.engstruct.2018.12.020

DO - 10.1016/j.engstruct.2018.12.020

M3 - Article

AN - SCOPUS:85058806534

VL - 181

SP - 550

EP - 561

JO - Engineering structures

JF - Engineering structures

SN - 0141-0296

ER -