Study On Mechanical Behavior Of End Bearing Of Reinforced Truss Laminated Slab

laminated slab is the most commonly used floor system in assembled building.The technical regulations of assembled concrete structure require that the reinforced bar of prefabricated slab should be extended from the end of the slab(referred to as beard bar).The existence of beard bar brings many inconveniences to the manufacture,transportation and field assembly of prefabricated components,and the repeated adjustment of beard bar in the process of transportation and assembly will lead to the decline of its performance.Some atlases and local codes allow the steel bars at the end of the slab to not extend,but the requirements for additional steel bars at the end of the slab to not extend the beard bars are inconsistent.Therefore,it is necessary to carry out a series of studies on the nonbeard-bar laminated slab,so as to provide a basis for the use of the non-beard-bar laminated slab.This paper mainly includes the following parts:(1)Performance test of end bearing of laminated slab under negative bending moment.Thirteen specimens were designed and manufactured,and the comparative tests were carried out under different span depth ratio for beard bar bearing at the end of plate,additional steel bar bearing without beard bar at the end of plate,beard bar bearing without beard bar at the end of plate and no additional steel bar support at the end of plate.The results show that the additional reinforcement is both bending and shearing resistant in the section,and can improve the negative moment bearing capacity of the plate end,which can be verified with the simulation results of the section.(2)Performance test of end bearing of laminated plate under positive bending moment.Five specimens were designed and manufactured,and the comparative tests were carried out under different span depth ratios for beard bar bearing at the end of plate,additional steel bar bearing without beard bar at the end of plate,beard bar bearing without beard bar at the end of plate and no additional steel bar support at the end of plate.The results show that the beard bar and the additional steel bar take part in the bending of the section as tension steel bar in the section,and the anchorage length of 15 d can ensure the yield of the steel bar.(3)Out-of-plane performance test of prefabricated truss composite slab-shear wall substructure.A specimens with beard bars at the end of prefabricated slab and additional reinforcement at the end of prefabricated slab without beard bars were designed and manufactured.Testing tests were carried out under vertical uniform load,horizontal reciprocating load and large deformation.The results show that the bearing capacity and stiffness of the structure with non-beard-bar laminated slab are higher than those of the structure with beard-bar laminated slab,but the energy dissipation of the non-beard-bar laminated slab is weaker than that of the beard-bar laminated slab after the inter-story displacement angle is 1/50.In order to ensure the integrity of composite slabs,it is necessary to install truss reinforcement,especially in the end region.(4)Substructure performance simulation of laminated slab with no beard bar at the end of slabs under different spans.In common structures with 2.9m storey height,130 mm thick floor slab are used.Under small span,the performance difference between nonbeard-bar laminated slab and normal laminated slab will occur within 1/500 of the interstory displacement angle.It is necessary to calculate the cross-sectional area of the additional reinforcement by simulation.Under the large span,when the inter-story displacement angle is less than 1/100,there is no difference between non-beard-bar laminated slab and normal laminated slab.Based on the conclusions of this paper,some design suggestions for laminated slab with no beard bar at the end are given.