Study On Mechanical Behavior Of Laminated Slab With Shear Keys

The laminated slab with shear keys is a new type of laminated slab.Compared with the traditional steel bar truss laminated slab,this kind of slab use concrete shear key to replace steel bar truss,which can reduce the reinforcement account and the project cost.At present,there are few research on laminated slab with shear keys in China.The existing test only study the basic mechanical characteristics such as bearing capacity of slab,and didn't conduct in-depth study of the loading process and failure mechanism.Therefore,this paper launched the mechanical behavior and calculation method of this kind of slab under vertical load.The specific work is as follow:Based on the ABAQUS and the static load test data of the existing one-way laminated slab with shear keys,the same finite element model of laminated slabs are established to simulate the loading process under vertical load,which compare with the test results.The results show that the load-deflection curves between simulation and test are consistent when the tie contact and friction contact is used separately between precast base plate and east-in-place layer of laminated slab,and the simulation is closer to the test results when the tie contact is used.Owning to the precast base plate and east-in-place layer dose not ensure firmly contact,considering that the safety of the structural design,the friction contact will be used in the interface between precast base plate and east-in-place layer during calculation.Through comparing the load-deflection curves and nephogram between laminated slab with shear keys and east-in-place slab under vertical load,the first principal stress change law of slab bottom concrete,the difference value of steel bar strain,steel bar stress and midspan displacement are analyzed.The influence of the number of shear keys on the load-deflection curves and side deformation graphics is also analyzed.The results show that the stiffness and bearing capacity of laminated slab will increase with the number of shear keys.When the number of shear keys in laminated slab reaches a certain extent,the load-deflection curves have basically coincided with the east-in-place slab.At the same time,the stiffness and bearing capacity will not change.Base on that,the shear force of shear keys in different position along the slab length direction is extracted to drawing the load-shear force curve.The shear force distribution law and the main factors of influence shear force size is summarized.The loading process of laminated slab with shear keys under the primary load and the secondary load are simulated.The load-deflection curves and stiffness value of laminated slab with shear keys with different spans under the two stress eondition are eompared.The span critical value of laminated slab under the two stress condition is given and the reason of laminated slab for calculating with the primary load component is explained.By changing different parameters,the loading process of 23 pieces of larninated slab under vertical load are simulated.The results show that when friction contact is used between precast base plate and cast-in-place layer,there has a certain influence on the yield load and yield displacement by changing the row spacing of shear key,the column spacing of shear key and the cross sectional of shear key.And the influence by changing column spacing is more obvious than row spacing.The influence of the concrete strength of shear key,the concrete strength of cast-in-place layer and the friction coefficient of interface on the yield load and yield displacement is relatively small.According to the results,the simplified calculation equations of flexural capacity and yield displacement of laminated slab with shear keys are recycled.