| Steel bridges have suffered heavy traffic load and environmental medium erosion for a long time in service,which made a large number of steel bridges appear fatigue cracks or corrosion damage,and greatly weakened the bearing capacity,seriously affecting the safe operation of bridges.Although the traditional repair method can achieve the reinforcement effect,it will bring new problems at the same time.What’s more,it is impossible to avoid the corrosion of the steel bridge caused by environmental.However,carbon fiber reinforced polymer(CFRP)can not only effectively avoid the shortcomings of traditional reinforcement methods,but also achieve better reinforcement effect,because of the advantages of light weight,high strength,good fatigue performance,corrosion resistance and easy construction,which was widely used in the field of reinforced concrete and has a perfect theoretical system.However,the research on improving the fatigue performance of steel bridges with CFRP is still in its early stage.In service,steel bridges will inevitably be affected by fatigue load and severe environment,which further aggravates the corrosion fatigue damage of steel bridges.Existing research shows that interface bonding performance is the key to the cooperation between CFRP-steel,and it is also the weakest part in the whole reinforcement system.Therefore,this paper has carried out an experimental study on fatigue performance of steel structures strengthened with CFRP under accelerated corrosion environment.The main research contents are as follows:(1)The fatigue performance test of CFRP-steel double strap joints under accelerated corrosion environment was carried out.The steel plates strengthed by CFRP with 75mm and 125mm in length were subjected to electric accelerated corrosion in 5%sodium chloride solution for 0h,24h,48h and 72h,and then fatigue tests with stress ratio of 0.1 were conducted until failure.The results show that in the first 48 hours of corrosion,the fatigue life decreases rapidly,when the corrosion time increases to 72 hours,the fatigue life decreases slowly.(2)The effects of corrosion time and CFRP bond length on fatigue life and stiffness reduction of steel structures strengthened with CFRP are analyzed,as well as the failure mechanism of steel structures strengthened with CFRP.The results show that the fatigue life of steel structures strengthened with 125mm CFRP is 4.8 times of 75 mm.The failure mode has a great influence on the fatigue life of strengthened specimens.The fatigue life of strengthened members is the highest when CFRP fracture or peeling failure of CFRP and bonding agent occurs,while the fatigue life of strengthened members is lower when peeling failure of steel and bonding interface occurs.The bond length of CFRP has little effect on the stiffness degradation of the specimen,which can be ignored.The longer the corrosion time is,the more severe the stiffness decay will be in the final failure.(3)The fatigue life expression of CFRP strengthened steel structure under accelerated corrosion environment is derived.The empirical coefficient in the expression is obtained according to experimental data,and the fatigue life of CFRP strengthened steel structure under accelerated corrosion environment is predicted and analyzed. |
