Anchorage And Seismic Performance Of Assembled Wall-beam Joints In Steel Tube Bundle Composite Shear Wall Structure

In recent years,the steel tube bundle composite shear wall structure system has been put forward and gradually applied in engineering practice,which has good bearing capacity,seismic performance and fire resistance.In this structure system,the wall-beam joint is the key part to realize the cooperative work of steel beam and shear wall.Therefore,based on the shortcomings of the existing wall-beam connection joints of the steel tube bundle combined shear wall structure,a new type of steel tube bundle combined shear wall structure anchoring the assembled wall-beam connection joints is proposed in this paper,which can realize the assembly construction and avoid the adverse effects of weld on the seismic performance of the joints.The proposal of this kind of joint has important reference value to engineering practice.This paper through the embedded parts drawing test and numerical simulation analysis of the mechanical properties of the key factors influencing the embedded parts,the thickness of the end plate is studied through finite element software ABAQUS,anchor length,concrete strength grade,axial compression ratio and embedded parts with and without baffles on five key parameters,such as assembly anchored wall the influence of the seismic performance of beam nodes,Finally,the failure mode,hysteresis performance,energy dissipation capacity and stiffness degradation of the joint are determined by pseudo-static tests.The details are as follows:(1)According to the pull-out test of joint anchoring embedded parts,the failure modes and anchoring bearing capacity of embedded parts in steel tube bundle combined shear wall and steel plate combined shear wall were analyzed.The test results show that the main failure phenomena of the specimens are spalling of concrete,bending of steel pipe wall and pulling out of embedded parts.The bond strength of embedded T-section steel and concrete is roughly distributed in the range of 0.45～0.67N/mm~2.The ultimate bearing capacity of steel tube bundle composite shear wall with baffle embedded parts and the minimum bearing capacity of steel plate composite shear wall without baffle embedded parts is 1405 k N and 740 k N,respectively.The anchorage bearing capacity of embedded baffle parts is about 1.5 times that of embedded baffle parts.Compared with the steel sheet-concrete composite shear wall,the steel bundle webs in the steel bundle composite shear wall structure can increase the anchorage capacity of the embedded parts by 27%～35.8%,and the ductility by 55%～110%.In addition,the finite element modeling was compared with the test results to verify the correctness of the modeling of embedded anchorage mechanism.(2)The finite element software ABAQUS was used to study the seismic performance of prefabricated wall-beam connection joints of steel tube bundle composite shear wall structure.Meanwhile,the influence rules of five key parameters on the seismic performance of such joints were analyzed,including end plate thickness,anchorage length,axial compression ratio,concrete strength and whether the embedded parts had baffles or not.The results showed that:(1)the bearing capacity of the node is mainly controlled by the beam end plastic hinge,in order to ensure the embedded parts in actual applications with good bearing capacity of anchor,should satisfy the embedded parts number of anchorage length is greater than 700 mm,the stud is greater than 12 structural requirements so as to make the embedded parts such as the ultimate bending moment of the beam end plastic bending moment,otherwise,the node embedded parts anchor damage will happen.(2)In the prefabricated wall-beam joint of steel tube bundle composite shear wall structure,the beam end load is transmitted to the shear wall mainly through the anchorage of embedded parts in the concrete.The internal forces of the pins on the embedded parts are not uniform.The bearing capacity of the embedded parts is determined by the smaller value of the shear strength of the pins and the compressive strength of the concrete.(3)The thickness of the end plate has little effect on the seismic performance of the joints,such as hysteretic curve,ductility,stiffness degradation and energy dissipation capacity.The value range of the end plate thickness is suggested to be 22～25mm.With the increase of the anchoring length of the embedded parts,the bearing capacity,ductility of the joints are enhanced.However,when the anchorage length increases to 700 mm,the seismic performance of the joint no longer changes significantly.Therefore,it is suggested that the anchorage length should be about 700 mm.The hysteretic performance,ductility and energy dissipation capacity of the joint will not have a great influence with the change of concrete strength grade.It is suggested that the strength grade of concrete should be C40.Axial compression ratio has little influence on joint bearing capacity.However,excessive axial compression ratio will make the concrete under the T-shaped steel webs of the embedded parts reach the compressive strength in advance.It is suggested that the axial compression ratio should be 0.3～0.5.At the same time,the anchorage length of the embedment parts can be effectively reduced and the steel consumption can be saved,which is economical to a certain extent.(3)Four full-scale wall-beam joint specimens were designed and subjected to pseudo-static loading tests.The seismic performance indexes such as failure mode,hysteresis curve of the joints were studied.The results show that:(1)The failure mode of specimen J-01 and J-04 is plastic hinge at the beam end,and the failure mode of specimen J-02 is the pull-out of the embedded part,at which time the lower flange has yielded.The failure mode of specimen J-03 is the pull-out of embedded parts.(2)Specimen J-01,J-02 and J-04 showed full "spindle shape" hysteresis curve with good energy dissipation capacity.The hysteretic curve of specimen J-03 is relatively pinched,showing "S-shaped" energy dissipation capacity is poor compared with other specimens.(3)The bearing capacity of specimens J-01,J-02 and J-04 is roughly the same and greater than that of specimen J-03.However,specimen J-01 and J-04 can achieve plastic hinge failure at the beam end,and the joint form is reasonable,while the joint J-03 is brittle failure,so it is not recommended to use.(4)The energy dissipation coefficient of the wall-beam joints with embedded baffles is between 2.01 and 2.451,and the equivalent viscous damping coefficient is between 0.32 and 0.391.The energy dissipation capacity of the wall-beam joints with embedded baffles is higher than that without embedded baffles.In addition,the joint stiffness can be increased by setting baffles at the end of the embedded parts,welding the end plates to the steel pipe wall and increasing the anchorage length of the embedded parts.(5)the failure mode,hysteresis curve and skeleton curve obtained by numerical simulation are in good agreement with the experimental results.It provides the basis for mutual verification between the test results and the finite element calculation results.