| The beamless floor is a structural system that the floor is directly placed on the column.The beamless floor system has many advantages such as simple shape of the formwork,the convenient support form during the construction process,the simple reinforcement and short construction period.The beamless floor system has been applied to underground garages and the building with large ground spans and high clear height requirements in recent years.Under normal load,the mechanical performance of the beamless floor structure system is simple and clear,and its design method and construction technique are relatively mature.However,the relevant design theory and design of the beamless floor is not mature under the special load(heap of soil,transportation vehicle wheel load,etc.),causing many collapse accidents at home and abroad.This paper mainly studies the mechanical performance of the beamless floor under normal load and the mechanical performance and strengthening measures under special load.The main contents are as follows:Firstly,this paper summarizes the application background and the research status of girderless floor at home and abroad.Besides,the types and composition of beamless floors are introduced and the analysis methods and application scope of beamless floors under conventional loads are sorted out.Secondly,combined with the residential background project,the selection of structural system,main load,structural characteristics and calculation method of basement floor are discussed,in this paper,the structural calculation software is used to complete the design of the basement flat slab under the normal load,the stress characteristics of the flat slab are analyzed,and the variation of the internal force of the structure and the crack development of the slab are investigated,the structural requirements of the flat slab,the selection of the column cap and the details are given.Thirdly,under the special load(roof pile load,vehicle wheel load),combined with the background engineering,PKPM and MIDAS finite element software are used to analyze the mechanical performance of the beamless floor structure under the special load,the internal force development and crack development of the beam-less floor structure of basement under special load are investigated.On this basis,according to the special load under the beam-less floor stress weak place,carries on the classification temporary reinforcement processing.For the condition of the load on the top plate,the method of changing the thickness of the top plate and the section of the column cap of the basement plate is adopted to reinforce the top plate,so that it can meet the requirement of use,the roof of the basement is strengthened by the way of steel column back to the roof to meet the use requirements of the construction lane.Finally,the finite element software ABAQUS is used to simulate and analyze the local mechanical behavior of the basement beamless floor,the deflection of floor,concrete stress,concrete damage and stress of reinforcing bar are analyzed.The results show that in practical engineering design,increasing the concrete strength grade and the steel bar strength grade of the column cap and the roof can effectively prevent the cracking of the concrete and improve the vertical bearing capacity of the beamless floor. |
