Study On Durability Of Steel/CFRP Bonding Interface Of Fatigue Damage And Erosion Under Cyclic Temperature And Humid Environment

Using CFRP material to repair defected steel structure can make full use of the advantage of CFRP, including high strength, good at resistance to corrosion and fatigue, and it is also convenient to use. Because of these, repairing steel structure using CFRP is well-known in repaired field. Attach CFRP plate to the surface of tension region of the flange of the steel beam is used to improve the bearing capacity of steel structure, corrosion fatigue repair and brittleness repair, etc. In order to make this method get more extensive application in engineering, good cohesiveness between CFRP plate and the surface of steel must be ensured. The structures in practical engineering often suffer from fatigue load and the influence of damp and hot environment. Therefore, in this article, the CFRP reinforcing steel plate bonding interface, and overload damage and tensile bearing capacity of the structure under hot and humid environment erosion is studied. The mean research contents and conclusions are as follow:(1) Experimental research on the durability of the joint steel plate and CFRP lap. Consider overload damage and heat cycle, overload injury is achieved by 300 times reciprocating load, the magnitude 0.1 to 0.7 times the ultimate bearing capacity; heat is circulated through a large dry-wet cycle test system to achieve a period of 24h, the drying time is 14h, water environment is 10h, temperature is 40℃, by the addition of 3.5% sodium chloride in water to simulate the marine environment. Static load tensile test results show: heat cycle 90 times and 180 times the maximum interface damp heat cycles after the specimen principal stress at failure decreased by 32.4% and 31.9%, indicating that the wet and dry cycles have a significant influence on the bonding interface performance, but three months later stabilized; after 180 heat cycles role, there is no overload damage and overload damage specimen maximum interface principal stress decreased by 31.9% and 33.0%, indicating that after the heat cycle overload injury on bond performance little effect.(2) Experimental Research on Durability of CFRP plate with reinforced steel beams defect. Consider overload damage and heat cycle. Overload damage by 400 times reciprocating load is achieved, the magnitude of 0.1 to 0.5 times the layer cracking load; four-point bending static load test results show:No heat cycle,90 times heat cycles and 180 heat cycles overload damage specimens defect layer cracking load than the undamaged specimen decreased by 8.6%,4.0% and 4.5%, indicating an overload injury have a certain influence on the cracking load; No heat cycle,90 times heat cycles and 180 heat cycles damage the specimen ultimate load than the undamaged specimen decreased by 2.2%-0.8% and 3.6%, indicating that excessive impact on the ultimate load carrying damage is not obvious. No damage of the specimen after 90 times heat cycles and 180 heat cycles, ultimate load decreased by 7.4% and 9.9%; and damage the specimen after 90 times heat cycles and 180 heat cycles ultimate load decreased by 6.7% and 13.1%. The above test results show that heat cycle and overload injuries have reduced defects CFRP plate reinforcement steel beams carrying capacity, but the impact is greater than the heat cycle overload damage.