Fatigue Performance Of Corroded Steel Plate Strengthened With CFRP Plates In Incomplete Unloading

Despite the protective and structural measures taken,the steel structure in the longterm corrosion environment can not avoid the occurrence of corrosion behavior,the surface rust pit produced by corrosion reduces the plasticity and fracture toughness of the steel structure material,causes local stress concentration,accelerates the crack germination and expansion,has a great impact on the fatigue performance of the steel structure.Carbon fiber reinforced composite materials(CFRP)with light quality,high strength,good corrosion resistance,strong fatigue and other advantages,the use of carbon fiber reinforced composite materials(CFRP)reinforced steel structure has been widely used,but in the process of reinforcing rusted steel structure,due to the steel structure unloading incomplete strain lag effect,reinforcement materials can not give full play to its performance and thus affect the reinforcement effect.In this paper,CFRP plate reinforcement rust editing steel plate as the research object,in view of the degree of rust,CFRP plate reinforcement stiffness and incomplete unloading degree on the CFRP plate reinforced rust plate fatigue performance,a systematic study was carried out.The specific research is as follows:(1)With the help of a three-dimensional non-contact scanner,the surface morphological characteristics of the rusted steel plate were determined,the rusted steel plate was reconstructed by a finite element model using the three-dimensional morphological data of the rusted steel plate,the CFRP plate bonded interface was modeled by using the spring unit,and the application of "incomplete lying unit" was used to apply the load application step of "incomplete unloading-holding reinforced load-second loading" in a finited-the-factor y/h-strain-to-the-concrete-plate." Finally,a finite element model of "variable thickness plate shell-spring-thickness plate shell" is established,a stress numerical analysis method for CFRP plate reinforced rust editing steel plate in incomplete unloading state is proposed,and a finite element batch calculation script function is written.(2)The stress of the CFRP plate reinforced rust editing steel plate in the incomplete unloading state was analyzed by Ansys finite element analysis software,the main factors affecting the stress distribution of the CFRP plate reinforced rust plate in the incomplete unloading state were analyzed,the degree of rust,CFRP plate stiffness and incomplete unloading degree were studied on the peak stress,the stress concentration coefficient and the conversion stress concentration coefficient of the rust plate on the rusted steel plate surface of the rusted steel plate,and based on the analysis results.A calculation model of the conversion stress concentration coefficient of CFRP plate reinforced rust editing steel plate was established,and the prediction value of the formula of the conversion stress concentration coefficient was compared with the finite element calculation value.(3)Based on the existing specification correction,the CFRP plate reinforced rust plate fatigue calculation model in incomplete unloading state,the model calculation results show that the increase of rust degree will lead to fatigue detection requirements can not be met,the use of CFRP plate reinforcement can reduce the calculation of positive stress amplitude,meet the fatigue testing requirements.(4)Based on the existing specification correction,the fatigue life calculation model of CFRP plate reinforced rust plate in incomplete unloading state is obtained,and the calculation results show that the increase of corrosion degree will reduce the fatigue life of the steel plate.