TY - JOUR

T1 - Mode I fatigue crack arrest in tensile steel members using prestressed CFRP plates

AU - Hosseini, Ardalan

AU - Ghafoori, Elyas

AU - Motavalli, Masoud

AU - Nussbaumer, Alain

AU - Zhao, Xiao Ling

N1 - Funding Information: The authors gratefully acknowledge the financial support provided by the Swiss National Science Foundation (Project No: 5211.00892.100.01) and the Australian Research Council (ARC) Linkage Grant (LP140100543). The authors also 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. Finally, support from S&P Clever Reinforcement Company AG, Switzerland, by providing the materials for the current study is acknowledged.

PY - 2017/6/29

Y1 - 2017/6/29

N2 - Numerous studies in the literature have shown that the strengthening of steel members using carbon fiber reinforced polymer (CFRP) composites can significantly extend the fatigue life of these structures. However, not enough attention has been focused on the potential of prestressed CFRP reinforcements for fatigue crack arrest in such members. In the current study, a simple analytical model is proposed to calculate the required prestressing level in the CFRP reinforcements in order to arrest the propagation of an existing fatigue crack in tensile steel members. Furthermore, a novel mechanical unbonded system is developed to anchor the high prestressing forces in CFRP reinforcements to the steel substrate using friction. A set of fatigue tests are performed on unstrengthened and strengthened precracked steel plates to verify the proposed model. The experimental results of the current study showed that the application of nonprestressed ultra-high modulus CFRP plates as externally bonded reinforcements can increase the fatigue life of precracked steel plates by a factor of 4.3. However, fatigue crack arrest is only possible when prestressed CFRPs of a certain prestressing level are used. Based on the analytical, numerical, and experimental results of the current study, it can be concluded that existing fatigue cracks in tensile steel members can be arrested using the proposed prestressed unbonded reinforcement system with the initial prestressing level calculated using the proposed model. In addition, some design recommendations are provided for fatigue crack arrest in practical cases.

AB - Numerous studies in the literature have shown that the strengthening of steel members using carbon fiber reinforced polymer (CFRP) composites can significantly extend the fatigue life of these structures. However, not enough attention has been focused on the potential of prestressed CFRP reinforcements for fatigue crack arrest in such members. In the current study, a simple analytical model is proposed to calculate the required prestressing level in the CFRP reinforcements in order to arrest the propagation of an existing fatigue crack in tensile steel members. Furthermore, a novel mechanical unbonded system is developed to anchor the high prestressing forces in CFRP reinforcements to the steel substrate using friction. A set of fatigue tests are performed on unstrengthened and strengthened precracked steel plates to verify the proposed model. The experimental results of the current study showed that the application of nonprestressed ultra-high modulus CFRP plates as externally bonded reinforcements can increase the fatigue life of precracked steel plates by a factor of 4.3. However, fatigue crack arrest is only possible when prestressed CFRPs of a certain prestressing level are used. Based on the analytical, numerical, and experimental results of the current study, it can be concluded that existing fatigue cracks in tensile steel members can be arrested using the proposed prestressed unbonded reinforcement system with the initial prestressing level calculated using the proposed model. In addition, some design recommendations are provided for fatigue crack arrest in practical cases.

KW - Carbon fiber reinforced polymer (CFRP)

KW - Crack arrest

KW - Fatigue strengthening

KW - Prestressed unbonded reinforcement (PUR)

KW - Steel structures

UR - http://www.scopus.com/inward/record.url?scp=85023647288&partnerID=8YFLogxK

U2 - 10.1016/j.compstruct.2017.06.056

DO - 10.1016/j.compstruct.2017.06.056

M3 - Article

AN - SCOPUS:85023647288

VL - 178

SP - 119

EP - 134

JO - Composite structures

JF - Composite structures

SN - 0263-8223

ER -