Force Analysis And Seismic Performance Of Prefabricated Shear Wall With Bolt Connection For Vertical Interface

Prefabricated building has the advantages of high industrialization level,fast construction efficiency,energy conservation and environmental protection,etc.Prefabricated shear wall structure is one of the main structural forms of prefabricated building,and also an important direction of housing industrialization development.In the assembled shear wall structure,there are horizontal joints and vertical joints.At present,in the research of assembled shear wall structure,there are more studies on horizontal joints and less on dry bolt connection of vertical joints.In this paper,the prefabricated shear wall with bolted vertical joints is studied to explore the feasibility of this connection mode.In this paper,the bolted shear wall is studied by means of finite element simulation and theoretical analysis.The reliability of the finite element model is verified by comparing with the experimental results.In this paper,19 shear wall calculation examples with vertical joints connected by bolts are designed to explore the influence of factors such as longitudinal reinforcement ratio,height-to-width ratio,axial compression ratio,number of bolts,interface friction coefficient and pore wall clearance on the bearing capacity,ductility and initial lateral stiffness of assembled shear wall members with vertical joints connected by bolts.The unevenness coefficient of bolt shear,the ratio of bolt group shear and the interface extrusion coefficient are explored.The value method of each coefficient is given preliminarily.Two groups of specimens were designed to explore the seismic performance differences between fabricated shear wall members and cast-in-place shear wall members.The main conclusions of this paper are as follows:(1)The factors that influence the bearing capacity of prefabricated shear wall with bolt connection are the ratio of longitudinal bars,the ratio of height to width,and the ratio of axial pressure.The bearing capacity of the member increases with the increase of the ratio of longitudinal reinforcement,and the ductility decreases slightly.When the aspect ratio is between 1 and 1.67,the bearing capacity of the member decreases with the increase of aspect ratio,and the ductility coefficient of the member is greater than 3,which is good.When the axial compression ratio is between 0.1 and 0.3,the bearing capacity of the members increases significantly with the increase of the axial compression ratio.When the axial compression ratio is 0.4,the bearing capacity of the members increases slowly,but the ductility decreases significantly,and the members have obvious brittleness.Therefore,it is necessary to control the axial compression ratio.(2)The initial lateral stiffness of the assembled shear wall is about 60%～75% of the initial stiffness of the cast-in-place shear wall.The increase of ring beam stiffness is helpful to increase the initial lateral stiffness of members.(3)At the vertical interface connection,the shear force of bolts at different positions is different,and the shear force of bolts group is obviously uneven.The shear law of bolt group is as follows: the shear force of bolt group in the upper and lower parts of the wall plate is small,and the shear force in the middle part is large.The shear uneven coefficient of bolt group fluctuates between 1.69 and 2.10,and the main factor affecting it is the pore wall clearance.With the increase of the pore wall clearance,the shear uneven coefficient of bolt group tends to increase.(4)The bolt group bears the combined action of shear force and pull force.The bolt group has no horizontal punching failure at the node and the node is safe.At the edge of the hole wall of the bolt group with large force,some areas are crushed and damaged.However,the small area does not affect the function of the whole hole wall and the member is close to its ultimate displacement.Therefore,it can be considered that the connecting nodes of the component are safe and reliable.(5)At the vertical interface joints,the shear force of bolt group accounts for about0.40～0.7 of the total shear force of the entire contact interface,and the influencing factors are mainly axial pressure ratio,interface friction coefficient and pore wall clearance.The shear ratio of bolts decreases with the increase of the axial compression ratio of members.However,considering the ductility of components and the shear non-uniformity of bolts,the axial compression ratio should be controlled.With the increase of the friction coefficient of the interface,the shear ratio of bolts decreases gradually.Therefore,it is suggested to increase the roughness of the contact interface.With the increase of hole wall clearance,bolt shear ratio will gradually reduce.The friction force at the vertical joint is caused by the extrusion pressure at the interface,and the factors affecting the interface extrusion coefficient are the aspect ratio and the pore wall clearance.At the same time,the increase of the interface friction coefficient tends to increase the interface extrusion coefficient.Considering the influence of many factors,the shear ratio and interfacial extrusion coefficient of bolts were fitted by multiple linear methods.(6)Under the horizontal action,there is a tendency of sliding at the vertical connection interface.At the initial stage,the friction force mainly plays the role of shear resistance.With the increase of horizontal displacement,the bolt rod starts to contact with the hole wall,and the bolt group plays the role of shear resistance.In this process,the shear resistance of bolts has hysteresis,and when the pore wall clearance is large,the hysteresis is obvious.(7)At low test axial compression ratio,the horizontal bearing capacity of the castin-place shear wall component is different from that of the assembled member which is designed with the unevenness coefficient of bolt shearing.The peak bearing capacity is less than 10%.During the monotonous horizontal loading and the reciprocating loading,most of the bolts are in the elastic state.(8)In the process of reciprocating loading,in terms of lateral stiffness,the lateral stiffness of assembled members degrades rapidly at the beginning,and slowly decreases after the members yield.The whole degradation law is the same as that of cast-in-place components.In terms of energy consumption,the energy dissipation coefficient or damping coefficient of assembled members increases gradually at the beginning,and then decreases slowly after the members reach the peak bearing capacity.At a low test axial pressure ratio,the maximum energy dissipation coefficient or damping coefficient of assembled components is different from that of cast-in-place components,and can be reduced by 0.7 to 0.8 times according to cast-in-place components.