| Cast-in-situ RC beam-slab floor system is the one which is widely used at present.It has great effect on the safety and economy.Beams and slabs of cast-in-situ RC floor system are integrated and act each other.Each of them contacts the others very tightly. They bear the load and are deformed together.Stiffness ratio of beam to slab and torsion of edge beam have a great impact in the deformation and force of the slab.But in the methods of designing the cast-in-situ RC floor system under the gravity load,beams and slabs are divided practically according to Code for design of concrete structures of china. When the section of bearing beam is too small,the method has great errors.In ACI code, Direct Method and Equivalent Frame Method are recommended to design any type of floor system,In which,to a certain extent,Stiffness ratio of beam to slab and torsion of edge beam are considered.But some problems of them require further study.In this paper,finite element analysis software ANSYS are used for floor system calculation model with finite elements to analyze 34 cast-in RC frame beam-slab structures of different length-width ratio and different section of slabs,beams and Columns under gravity loads.The influence of stiffness ratio of beam to slab is studied, the distinguishing criteria of"two-way edge-supported slabs"and"corner-supported slabs"is presented by analyzing the results of finite element method and simplified method.When the al2/l1,of the Short span is greater than 5,simplified method can be used for Reinforcement Design with acceptable error.By analyzing the results of finite element method and simplified method Equivalent Frame Method,the latter method 's applicability and precision is estimated.On the whole,the error of the force and the deformation is small.External negative moment's error becomes great while the section of beam or slab is too big. |
