Stress Mechanism Study And Structural Design Optimization Of Prestressed Girderless Floor

The unbonded prestressed girderless floor is a new type of structure which is optimized based on the ordinary girderless floor.Its advantages lie in the characteristics of thinner thickness,lighter self-weight,lower cost and so on,which can reduce the height of the building to the maximum extent.The general efficiency is outstanding.However,there is no unified method or basis for the structural design of this new type of floor at present.In order to solve these problems,this paper studies the stress mechanism and structural design of unbonded prestressed girderless floor.On the basis of summarizing the previous research work,this paper mainly completed the following research work:1.On the basis of elastic sheet bending theory,the equilibrium equation of prestressed girderless floor is established,the two-way stiffness of prestressed girderless floor and the maximum deflection of slab are calculated.By means of finite element method,the stress mechanism of prestressed girderless floor is studied in elastic range,and it is verified that the design of prestressed girderless floor structure can be based on the equivalent frame,bending moment distribution and load balance.2.Based on the four kinds of unbonded prestressed tendons(supporting slab and column caps)which are accepted,four schemes are simulated and calculated.It is determined that the optimal structural scheme is that the reinforcement centralized width of column strip and midspan slab.3.Under the action of even load,the limit analysis of prestressed girderless floor is carried out.Based on kinematic method,the limit load of prestressed slab is calculated under the boundary condition of four edges clamped,three edges clamped and one edge free.Through Pushover design,study of single-span prestressed slab is carried out,which includes three stages: yield state of prestressed slab,failure of the first prestressed tendon and complete destruction of whole slab.It is found that the prestressed girderless floor can reduce the punching effectively to meet the checking of slab-column connection punching.4.On the basis of the theoretical analysis and simulation,the optimum suggestions for the design of prestressed girderless floor are given,including the selection of prestressed system,the selection of slab thickness and economic span,etc.Finally,through the project example design of unbonded prestressed girderless floor in Zone Aof the underground garage of Jinhui Square.The research above are verified.