| Reinforced concrete structures are the most common form of construction currently in use.In the reinforced concrete frame structure,the beam-column joint connects the beam and the column member,and acts as a force-transmitting hub to play the role of internal force transmission and distribution.However,in the earthquake fortification area,there are a large number of reinforced concrete frames that are designed according to non-seismic design or in the past due to the old seismic design.The seismic strengthening is urgently needed,and the shear reinforcement of the nodes is the key link.With the advantages of carbon fiber-reinforced polymer(CFRP)gradually acknowledged,it has been widely used in the construction of reinforced concrete structures.However,the research on node reinforcement at this stage is basically limited to planar frame nodes.Due to the existence of orthogonal beams,most nodes in the structure are 3D RC beam-column joints making the research results difficult to apply in practical engineering.Therefore,it is of great significance for the reinforcement research of 3D RC beam-column joints.Due to the limitation of the number of test specimens,the finite element analysis can solve this problem well.More specimen models are established to study the influence of different influencing factors on the reinforcement efficiency of CFRP strengthened space frame nodes.In this paper,the nonlinear finite element analysis software is used to simulate 3D RC beam-column interior joints.In order to be close to the actual structural stress,the bond slip between the steel and CFRP and the concrete interface is considered in the modeling process.A total of 80 test piece models were designed based on different parameter combinations,including 60 test pieces and 20 unreinforced test pieces.The crack development,loaddisplacement curve,concrete stress,CFRP strain and deformation of the reinforced and unreinforced specimens are compared.The calculation results analyze the influence degree and difference of different parameters on the shear capacity of the CFRP reinforced 3D RC beamcolumn interior joints.Including: CFRP layer number,CFRP bonding method,axial compression ratio,orthogonal beam height,width and quantity,and initial damage of orthogonal beam.The simulation results show that:(1)the shear capacity of the joint increases with the increase of the number of CFRP layers;(2)due to the influence of the orthogonal beam,different CFRP reinforcement forms result in different node reinforcement effects.(3)Within a certain range,the increase of the axial compression ratio will increase the shear capacity of the joint,but the reinforcement ratio of CFRP is decreasing.(4)The existence of orthogonal beams can improve the shear capacity of the joints.However,when the spatial dimension of the orthogonal beam is large,the shrinkage rate of the CFRP is lowered.(5)The yielding of the longitudinal beam of the straight beam will cause the constraint of the core area of the node to weaken,thus reducing the ultimate bearing capacity of the node. |
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