Study On The Degradation Of Bonding Properties Of Corroded Steel Plate Strengthened By CFRP Under Alternate Dry-Wet Environment

At present,a large number of existing steel structures are often corroded due to the erosion of the surrounding environment.Both the bearing capacity and fatigue performance of corroded steel structures will decrease due to the weakening of the cross section and the stress concentration effect caused by the uneven surface.As a new type of material,carbon fiber reinforced polymer（CFRP）has been widely used in the field of the strengthening of existing steel structures due to its advantages of high strength to weight ratio and the resistance to the fatigue load and the environmental erosion.The reinforcement of the steel structures with the CFRP bonding method can effectively restore its local stiffness lost due to corrosion and reduce the stress concentration at the erosion pits,thereby improving its load bearing capacity.Since CFRP materials are mostly used to reinforce existing steel structures,it is necessary to consider the effect of steel corrosion on the reinforcement effect.In addition,since the steel structure reinforced with CFRP material will continue to be eroded by the surrounding environment,it is necessary to study the long-term performance of the CFRP reinforced steel structure system under environmental erosion.Based on the above background,this paper studied the effect of the corrosion on the bond strength between CFRP plate and steel plate,the degradation law of the bond behavior under alternate dry-wet environment was also studied.The main content of this paper included the following aspects:（1）The environmental erosion experiments were conducted by a dry and wet alternate test device.The tensile tests of the steel and the CFRP plate,adhesive and adhesive-steel specimens with the duration of 0,1,3,6 weeks were conducted to acquire the material degradation.Using the self-made load device and the non-contact displacement measuring technology,the interfacial shearing tests of the CFRP plate-corroded steel plate single lap specimens with duration of 0,1,3,6 weeks were also conducted and the corresponding bond behavior were obtained.（2）Using the non-contact surface scanning technology,the surfaces of the corroded steel plates composing the CFRP plate-corroded steel plate single lap specimens were tested and the 3D models of the surfaces were obtained.Based on the scanning results,the corrosion parameters such as the non-uniform volume loss ratioξ_s,the root mean square height S_q,the developed interfacial area ratio S_dr,the factual dimension D,the pit depth h,the pit depth-to width ratio Ar and the pit density P_d were acquired.To analysis the effect of the corrosion on the bond strength,the relationships between these corrosion parameters and the bond strength of the CFRP plate-corroded steel plate single lap specimens were established.（3）By comparing the results of the tensile tests of the CFRP plate,adhesive and adhesive-steel specimen with different durations,the degradation laws of these materials were obtained.By analyzing the results of the interfacial shear tests of the CFRP plate-corroded steel plate single lap specimens,the bond behavior containing the load-displacement relationship,the interfacial shear stress distribution and the bond-slip behavior was obtained,its degradation law under alternate dry-wet environment and the corresponding mechanism were also studied.