Research On Analytical Methods For Cast-in-situ Reinforced Concrete Floor Structure

At present,most of the analysis methods of one-way slabs and two-way slabs stiffened with beams along the column centerline ignore the vertical deformation of support beams.While the beam's cross-section depth in practical project usually take 1/18 to 1/10 of the beam's span length,so the vertical deformation and torsion deformation of support beam have effects on the internal forces distribution of slabs. Therefore it is necessary to research the method of structural analysis considering the interaction of plate and beam in floor structure.About the ultimate analysis issues of the floor structure,this paper has mainly. analyzed slab failure mode and beam-slab failure mode under the ultimate state,as well as considered the effects to internal forces which are result from the torsion beam to make the results more realistic.The main work of this paper as follows:(1) Derived the formula of the ultimate load or limit moment for beam-slab failure mode.Based on the mature theory of slab failure mode,the paper derived the formula of the ultimate load or limit moment in the three possible failure modes,which consider the load-carrying capacity of supporting beam in both the longitudinal and the transverse directions.(2) the effect of the edge beam's torsion.Analyzed the effects of the torsion of beam on the internal forces of the exterior slabs when calculating the internal forces of the edge slabs and the corner slabs,and the rule of the internal forces of slabs with the beam cross-section depth.(3) Compared and analyzed the distinction of calculating internal forces between the table method and the equivalent-frame method,and the distinction of calculating reinforcement and defection for the table method,the ultimate analysis and the equivalent-frame method.Based on the result of this paper,the main conclusions can be obtained as follows: (1) under the same condition,the slabs in the floor are more vulnerable to come to be beam-slab failure mode;(2) the moment calculated by the direct design method is higher than that of the equivalent-frame method;(3) the moment in the interior slabs calculated by table method is higher than that of the equivalent-frame method;(4) the changes of the stiffness ratio of beam to slab have much effect on the negative moment at the first supporting of the slabs in the edge and in the corner;(5) the reinforcements calculate by the limit analysis method is minimum.