| Prefabricated concrete structure,as an important structural form of new building industrialization and green development in China,has the advantages of fast construction speed,short construction cycle,safety and environmental protection,lower cost and reusable compared with traditional cast-in-place buildings.The connection mode of beam-column joints in prefabricated concrete structures is the fundamental to distinguish prefabricated structures from cast-in-place structures,and is also the core factor affecting the seismic performance of the whole structure.Therefore,it is of great significance to study the seismic performance of prefabricated concrete structures.In view of the present assembly integral joint construction complex and have certain technical requirements for the construction personnel,long construction period,high construction cost,construction quality is difficult to be guaranteed,this topic proposed a new type of assembled concrete beam-column L-shaped steel joint,and carried out research on it.First of all,the design and construction of four new prefabricated specimens and a cast-in-situ node specimen,and the case for quasi static test research,through the observation of the crack development of the five specimens of each node specimen key parts of reinforcement,concrete strain,hysteresis curves,skeleton curves,ductility coefficient,viscous damping coefficient of seismic indicators,such as the new type of prefabricated concrete beam-column L stress mechanism,damage forms of reinforced connecting node and seismic performance.Finally,using the finite element analysis software ABAQUS,according to the actual size to build new finite element model of nodes precast and cast-in-place node specimen stress cloud and deformation figure,stress strain curve and hysteresis curve etc.The simulation results,and compared with the test results,verify the accuracy of the finite element model is established,and then to carry out the parameter analysis,studies the influence of different parameters on seismic performance of specimens.Based on the test and finite element results,the shear capacity calculation formula of the joint is proposed.Research shows that:(1)through low reversed cyclic loading test,found that increasing the node area after pouring concrete area,L reinforcement length and area of composite beams of concrete strength,can effectively improve the node specimen after water area and the bonding ability between prefabricated,to improve the bearing capacity of node specimen,energy dissipation capacity and ductility performance goal,preset steel tube can effectively improve the node in the column of the initial stiffness.(2)ZP-2 node specimen damage forms belong to shear failure,this is because when the diagonal inclined cracks after the joint core concrete,shear transfer by oblique compression bar mechanism transition to level stirrup under horizontal force,longitudinal reinforcement vertical force and axial pressure and inclined cracks between concrete truss stress mechanism of the bite,ZP-2 node USES is short L steel,is to reduce the vertical force component,thereby increasing the burden of the concrete,so there will be a node shear failure phenomenon.(3)According to the stress cloud of reinforcement,XJ-1,ZP-1,ZP-3 and ZP-4 joints belong to bending failure of beam end,while ZP-2 joints belong to shear failure of node area.The axial pressure is beneficial to the shear of the joint within a certain range,which can improve the initial stiffness and ultimate bearing capacity of the joint.When the axial pressure is increased beyond a certain range,the ductility of the joint decreases somewhat.(4)On the premise of related parameters is set up correctly,the finite element simulation results can reflect to some extent real mechanical characteristics of specimens,but because of the bond-slip of reinforced concrete structure,nonlinear behavior of concrete cracking and knead shrinkage is difficult to simulate,there still exists certain error compared with the actual situation,and has some limitations.(5)By comparing and analyzing the shear capacity obtained by theoretical calculation with the shear capacity obtained by experimental study and finite element simulation,it can be seen that the numerical coincidence degree between the three is relatively high,and the error is less than 15%,which indicates that the shear capacity formula proposed by the new prefabricated L-bar joint is more accurate and meets the needs of design and application. |
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