Study On The Mechanical Behavior Of FRP Reinforced Beam-column Connections With Glued-in In Rods For Timber Structures

The design of connections in timber structure is related to the safety,reliability and stability of the whole building structure.The research on the mechanical properties of various forms of joints is the primary work for establishing the design method.The gluedin-rods connections is one of the joint forms considered in the research of glulam timber structure in recent years,but the ductility and energy dissipation of the pure glued-in steel rod joints are insufficient.In view of this problem,based on the existing research of the research group,this thesis proposes reinforced beam-column connections with glued-in rods using different FRP materials.The failure mode and hysteretic performance of the beam-column glued-in-rod joints with and without reinforcement under low-reversed cyclic loading are analyzed by experimental and numerical simulation methods,and the effects of FRP bonding layers and reinforcement methods on the mechanical performance of reinforced beam column joints are discussed.The main research contents and conclusions are as follows:(1)Based on the installation deviation of the existing beam-column connections with glued-in rods in the research group,an improved joint is proposed and checked by finite element analysis method;Aiming at the relatively poor ductility and energy consumption of pure glued-in rod joints,a reinforcing method using fiber reinforced polymer(FRP)to paste the beam-column joints with glued-in rods is proposed,and finite element analysis is carried out based on the preliminary design of the pasting scheme.The results show that the fiber-reinforced joint can effectively improve the bearing capacity,which is beneficial to earthquake resistance,and the optimal bonding method is clarified.(2)The pseudo-static test of CFRP and GFRP reinforced beam-column joints and pure glued-in rod joints are carried out.The results show that the ultimate bearing capacity and ductility can be effectively improved.When the pure glued-in rod joint is damaged,cracks along the grain appear on the lower side of the beam-end,and the failure is sudden;the FRP-reinforced joint has no cracks on the surface of the wood,and the joint failure mode is fiber failure.(3)The validity of the numerical simulation is confirmed by comparing and analyzing the experimental and numerical simulation results of the pure glued-in rod joint with the GFRP-reinforced joint.It was preliminarily concluded that the deviation between the test and simulation results of CFRP reinforced joints might be caused by the defect of fiber fabric.Furthermore,the life-and-death element technique is introduced and the defects of the fiber fabric are considered,it is proved that the adjusted finite element calculation results are more reliable.(4)In order to improve the strengthening effect of joints,parameterized numerical simulation was carried out,which considers the influence of the number of fiber sheet layers and reinforcement methods.The results show that the bearing capacity of joints increases with the increase of the number of fiber sheet layers.The separate reinforcement method can significantly improve the bearing capacity of the joint while saving the amount of FRP sheets,which has a better performance enhancement effect.