Study On Prestress Effectiveness In Connection Of Precast Concrete Slabs Assembled By Preloading

Prefabricated assembly rate is an important indicator to measure the degree of assembly of a building structure.At present,the prefabricated assembly rate of floor slabs is low,and the full prefabricated slab is the fundamental solution to this problem.To solve this problem,a fully prefabricated slab structure and its preloading assembly method is proposed,aiming to establish prestressing on assembly parts to compensate for the inadequacies of traditional assembly methods in terms of interface crack resistance,leak resistance,and joint integrity.On this basis,this paper further studies the feasibility of this method and its prestressed connection effects.The main work of this paper is as follows:(1)A fully prefabricated floor structure and its preloading assembly method is invented,elastically analyzing the assembly scheme and effect of the method.Through the analysis of the deflection evolution of the preloaded assembly floor,the theoretical calculation formulas of the preloading method,position and size are deduced;then according to the stress calculation theory of concrete section,the formulas for calculating the stress of the concrete section under tension and compression on the joints at the assembly site are deduced,which preliminarily verifies the feasibility of the preloading method to establish the prestress at the floor assembly site.(2)The prestressed joint effects of two preloaded prefabricated one-way prefabricated floor slabs were tested,and the load-deflection curves of the slab during preloading and the strain values of the concrete at the joints at the joint were obtained.The test results show that the deflection increases linearly with the load during the preloading process,and the floor is in the elastic working phase.After the preloading is removed,sufficient prestress can be established at the assembly site.(3)The finite element analysis software Abaqus was used to conduct elasto-plastic simulation analysis of preloaded prestressed one-way boards and two-way boards with 24 different parameters,the stress and strain distribution of the cross section at the joint were studied,and the effects of the preloading position,effective prestress and the ratio of span to height on the prestressed connection of the preloaded floor were analyzed.The simulation results show that the preloading method can establish prestress at the assembly site;the closer the preloading position is to the edge of the floor,the greater the effective prestress and the ratio of span to height,the better the prestressed connection of the preloaded assembly method,but the greater the required preloading force;different from the one-way plate,the assembly prestress of the compression edge of the cross-section of the two-way plate shows an obvious “arched” uneven distribution along the length of the joint.(4)Based on the prestressed assembly method elastic theory analysis model,it is compared with the finite element simulation results,and the correction coefficient is obtained through the Origin fitting,thereby modifying the elastic theory model of the preloaded assembly method,provide a more reliable basis for engineering applications.