Experimental And Theoretical Research On CFRP-Steel Compositeplate Under Uniaxial Compression

Due to the advantages of high strength,light weight and high industrialization,Steel structures have been widely applied in modern engineering structure.There will inevitably be various kinds of damage because of the severe environment and holes,when the damage is accumulated to a certain extent or the opening is too large,the mechanical properties of the steel structure will be seriously affected.Compared to the disadvantages of traditional welding,bolt connection and bonding,fiber reinforced composites(FRP)have been widely used in the field of steel structure reinforcement due to its advantages,such as lightweight,high strength,corrosion resistance,excellent design ability and convenient processing.At present,many researches home and abroad have done a lot of experimental research on the steel structure reinforced by FRP,but it is basically a qualitative study of the reinforcement effect from the point of the structure.It is difficult to put forward a universal method of design and calculating the ultimate bearing capacity.In this paper,the steel structure reinforced by FRP is considered as a composite plate members composed of multiple FRP-steel composite plates.Combined with the existing calculation methods of steel structure buckling and ultimate bearing capacity,the mechanical properties of FRP-steel composite plates and their components were studied using the methods of experiments,theoretical derivation,numerical simulation and so on.The research contents and achievements are as follows:(1)Experimental study on compression performance of FRP-steel composite plateA test device for in-plane compression of plate is designed,and its reliability is verified through the results of the experiments.A total of 40 FRP-steel composite plates are designed,and the parameters including the width to thickness ratio,boundary conditions,single(double)surface patching and the amount of cloth,also a total of 36 composite plates with holes are designed considered of the width to thickness ratio,the size of the hole and the single(double)surface patching,hole locations and so on.(2)Theoretical and numerical research on the buckling of FRP-steel composite plate.Based on the large deflection theory,a formula for calculating the stiffness of composite panels is proposed and simplified.Furthermore,a calculation method of the buckling load of FRP-steel composite plate considering the FRP orthotropic and hole parameters is proposed.Because of the limited number of tests,the stiffness correction coefficient?_D and the buckling coefficient K_u in calculating the buckling load formula are studied by numerical method.The parameterized numerical model of the composite plate was established by combining of the module model input files and the scripted psf files.A large number of parametric analyses,9438 models in total,were performed on the parameter analysis of?_D and K_u.The effects of parameters such as boundary conditions,plate length-to-width ratio,hole size,and hole locations are considered.(3)A study on the calculation method of ultimate load of CFRP-steel composite plateBased on the calculation method of the buckling load of the composite plate,the winter strength formula of the ultimate load of the FRP-steel composite plate is proposed.The formula is used to calculate the ultimate load of FRP-steel composite plate test,and the results are compared with the results calculated by the existing steel plate limit load calculation formula.The reliability of winter strength formula method for the ultimate load of FRP-steel composite plate is proved.(4)Experimental study on the FRP-steel composite membersFor further study the compression performance of FRP-steel composite members,Three square steel tubes and twelve FRP-steel components tube were designed.Through monotonic loading test,the load displacement curve and bearing capacity of members are achieved.It provides the experimental basis for the design and verification of composite plate members.(5)Calculation method of FRP-steel composite members under compressionThe ultimate load calculation methods of the compression steel members in various countries are introduced and compared.And the slenderness ratio factor?_c and the plate slenderness ratio factor?_p,which reflect the overall stability of the component and the stability of local buckling,are presented.Combined with the calculation method for buckling loads of composite plate in chapters 3 and 5,the winter strength formula of the ultimate load of the composite plate in chapter 5,equivalent section model in chapter 7,and the calculation method of CSA S136-07 in chapter 7,a calculation method of FRP-steel composite members under compression is proposed,which considers the boundary conditions,the hole'size,the hole'location and so on.According to this method,the ultimate loads of the existing tests are calculated and compared.The feasibility of the method to calculate the ultimate load of FRP-steel composite members is verified.