TY - JOUR

T1 - Experimental investigation on the CFRP strengthening efficiency of steel plates with inclined cracks under fatigue loading

AU - Aljabar, N. J.

AU - Zhao, X. L.

AU - Al-Mahaidi, R.

AU - Ghafoori, E.

AU - Motavalli, M.

AU - Koay, Y. C.

N1 - Funding Information: In the present paper, the fatigue performance and the fatigue behaviour were investigated first for steel plates with inclined cracks strengthened with composite materials with different mechanical properties. In this study, the results of experiments on specimens with damage levels ranging between 2% and 40%, which were strengthened with two different configurations, were presented. Furthermore, strengthening systems with different fibre orientation were suggested for steel plates with inclined cracks, and a recommendation was made for the best fibre angle relative to the initial crack line. This study is a part of a large research program on the CFRP strengthening of metallic bridges subjected to mixed-mode (I + II) loading at Monash University in collaboration with Swinburne University of Technology, and the Swiss Federal Laboratories for Materials Science and Technology (Empa), which is sponsored by the Australian Research Council, VicRoads and S&P Clever Reinforcement Company AG. This project is funded by the Australian Research Council through an ARC Linkage Grant ( LP140100543 ) with VicRoads and S&P Clever Reinforcement Company AG as industry partners. The first author wishes to thank the Higher Committee for Education Development in Iraq for sponsoring his research at Monash University. Thanks are given to all the technical staff in the Civil engineering laboratory at Monash University for their support.

PY - 2018/10/1

Y1 - 2018/10/1

N2 - Employing advanced material such as carbon‐fibre‐reinforced‐polymer (CFRP) in tension fatigue strengthening of aged roads and railway bridges have shown a great capability of arresting or delaying crack initiation and/or propagation in steel structures. However, it is not clear whether the fatigue behaviour and the CFRP strengthening efficiency is the same when the cracked-steel elements exhibit a state of complex loading. The aim of this paper is to investigate the fatigue behaviour of the CFRP strengthening of steel plates with central initial inclined cracks with a focus on the effect of the CFRP properties. The initial slit-like cracks were oriented to introduce a state of combined action of tension (mode-I) and shear (mode II) stresses at the crack tips. The key parameters in this study are the mixed‐mode (shear to tension stresses) ratio, the crack-starter length ratio (initial crack length to the plate width), patching configurations, and mechanical properties of the composite material. All the test specimens were artificially notched with central cracks of different damage levels. This study covered the fatigue performance of steel plates strengthened with two configurations of composite materials of different tensile stiffness (high modulus CFRP sheets, and normal modulus CFRP plates). Furthermore, the efficiency of strengthening systems of different fibre orientation relative to the initial crack angle was investigated. The outcomes of this study are extending the current knowledge of the CFRP strengthening to its applications on metal plates contain defects subjected to mixed-mode fatigue loading.

AB - Employing advanced material such as carbon‐fibre‐reinforced‐polymer (CFRP) in tension fatigue strengthening of aged roads and railway bridges have shown a great capability of arresting or delaying crack initiation and/or propagation in steel structures. However, it is not clear whether the fatigue behaviour and the CFRP strengthening efficiency is the same when the cracked-steel elements exhibit a state of complex loading. The aim of this paper is to investigate the fatigue behaviour of the CFRP strengthening of steel plates with central initial inclined cracks with a focus on the effect of the CFRP properties. The initial slit-like cracks were oriented to introduce a state of combined action of tension (mode-I) and shear (mode II) stresses at the crack tips. The key parameters in this study are the mixed‐mode (shear to tension stresses) ratio, the crack-starter length ratio (initial crack length to the plate width), patching configurations, and mechanical properties of the composite material. All the test specimens were artificially notched with central cracks of different damage levels. This study covered the fatigue performance of steel plates strengthened with two configurations of composite materials of different tensile stiffness (high modulus CFRP sheets, and normal modulus CFRP plates). Furthermore, the efficiency of strengthening systems of different fibre orientation relative to the initial crack angle was investigated. The outcomes of this study are extending the current knowledge of the CFRP strengthening to its applications on metal plates contain defects subjected to mixed-mode fatigue loading.

KW - CFRP properties

KW - CFRP strengthening

KW - Damage degree

KW - Fatigue life

KW - Fatigue test

KW - Inclined crack

KW - Initial crack length

KW - Mixed-mode (I + II)

KW - Steel plate

UR - http://www.scopus.com/inward/record.url?scp=85049045673&partnerID=8YFLogxK

U2 - 10.1016/j.engstruct.2018.06.074

DO - 10.1016/j.engstruct.2018.06.074

M3 - Article

AN - SCOPUS:85049045673

VL - 172

SP - 877

EP - 890

JO - Engineering structures

JF - Engineering structures

SN - 0141-0296

ER -