Stress Analysis And Engineering Application For Large-Span Concrete Hollow Floor

With the development of national economy and improvement of building functional requirements, large span and large space structure arises at the historic moment. Hollow floor application's main purpose is to reduce weight, but the hollow floor system was applied to large span and large space structure, the design and calculation are many key problems need to be solved. Took a teaching training guarantee housing project as an example,the internal force calculation for the large-span hollow floor, the section of reinforcement, seismic analysis and fire disaster analysis are compared. The main research content is as follows:(1) Using PKPM, YJK, MIDAS/Gen three kinds of commonly used calculation program,typical structure of large span prestressed concrete cast-in-situ hollow floor engineering are calculated, through the comparison and analysis of the results, the empirical method of section reinforcement design and internal force determination of structure is presented. According to the internal force determined, the reinforcement of the large-span floor were calculated.(2)Considering the influence of the column and beam, the integral model is established,using the finite element software ABAQUS for static and modal analysis of structure. The results show that under the vertical static load, the stress distribution trend similar to the two-way slab under uniformly distributed loads. Extreme stress appears in the bottom of rib beam of the central area and the top of support of rib beam of long span direction; Part of 1/3 span is plastic hinge line area, which in the reinforcement design should be strengthened. Modal analysis showed that because the floor quality is very big, the first vibration mode is of the combination of translational and torsional deformation, dominated by torsion; the lateral displacement along the direction of the long span is greater than the displacement of the direction of short span . At the same time due to large span, the torsion beam cannot be ignored,so in integral calculation,beam torque should not be reduced.(3) Based on dynamic time history analysis method, the action of dynamic response of the large-span hollow floor structure under unidirectional and bidirectional horizontal earthquake are analyzed, the results show that the displacement of large span cast-in-situ hollow floor under unidirectional and bidirectional seismic action meet the requirement of serviceability limit states, the reinforcement design methods based on the internal force in this paper is reasonable, meanwhile cast-in-situ hollow floor is feasible in engineering, but it must pay attention to strengthening the weak parts of the structure.(4)Based on sequential thermo-mechanical coupling analysis method, we took the cast hollow floor structure to carry on the temperature and deformation analysis, the results show: In the analysis of initial 40min, the temperature of the hollow slab and column sections rises rapidly in the fire surface, this trend tends to be smooth after; Hollow slab has good heat insulation in 300 minutes of temperature rising process, showing high temperature state only in the range of 300mm above the surface of the fire; The calculation of the limited fire-endurance of the slab and the column by using the deformation criterion is carried out.