Effects Of Openings On The Performance Of Long-span Prestressed Beam

With the development of economy,the high-rise and super long-span prestressed concrete structures are increasing.Beam openings can save auxiliary facilities,increase building space,reduce weight,has higher application value.However,beam openings destroy the integrity and continuity of the structure,will directly affect the safety of the structure,so it is necessary to conduct further research on the opening characteristics of prestressed concrete,to guide the engineering practice.Based on the prestressed beam is simulated with finite element software,study on different hole shape and size and spacing of holes corresponding with characteristics,analyzes the stress,deflection and ultimate bearing capacity.Comparison of different models of prestressed concrete beam with openings under the condition of more than "handbook of concrete structure tectonic" for the maximum opening hole size and the minimum opening hole spacing.The main research work and conclusions are as follows:(1)The present situation and development of the research on the long span prestressed concrete structure and the beam with openings through literature survey,analysis of prestressed concrete structure mechanical model and constitutive relation of concrete,provide the basis for simulation and analysis of the prestressed beam with openings.(2)Setting and calculation of the engineering survey by PKPM and mechanics calculation,for the back of the 5 Analysis group.Analysis of prestressed concrete beam,concrete beam and prestressed concrete beams with openings three different models of change rule of stress and deflection,get the main effect of the range of beam openings for surrounding openings,prestressed tendons can improve the mechanical properties and deformation of the beam,compared with the concrete beam with openings the stress and deflection is decreased by 83%and 50%.(3)With hole size and hole spacing for variable,simulation of prestressed concrete beam with open circular hole.Results with the hole size increases or hole spacing decreases,the increase of stress and deflection of the beam,the ultimate bearing capacity decreases.To ensure the maximum opening size structure can be more than 41.67%the provisions of tectonic handbook,the minimum hole spacing than the the provisions of tectonic handbook decreased by 56.25%.(4)With hole size and hole spacing for variable,simulation of prestressed concrete beam with open square hole.Results with the hole size increases or hole spacing decreases,the increase of stress and deflection of the beam,the ultimate bearing capacity decreases.To ensure the maximum opening size structure can be more than 33.33%the provisions of tectonic handbook,the minimum hole spacing than the the provisions of tectonic handbook decreased by 56.25%.(5)Influence of hole spacing relative hole size of prestressed concrete beams with smaller,it is better than the square hole to open the circular hole on the prestressed concrete beam,to ensure the structural safety and functional requirements on the proposal to give priority to the selection of the circular hole method.