Research On Seismic Design Method Of RCS Composite Frame Considering The Effect Of Cast In Place Floor Slab

The composite frame structure of reinforced concrete column and steel beam(RCS)consists of the reinforced concrete column and steel beam. This architecture system makes full use of advantages of each component of concrete column and steel beam. At present, the research of this system is mainly concentrated in the aspect of beam and column node, but the study on the overall seismic performance of the composite frame structure of RCS is limited. This article mainly studies the influence of cast-in-situ floor slab on the yield mechanism of the composite frame of RCS and compares the seismic performance of the composite frame of RCS with those of other types of frames.For the composite frame structure of RCS, this article respectively establishes the finite element models of floor slab structure and no floor slab structure and evaluates the seismic performance of two kinds of structure under different earthquake levels by nonlinear static analysis. It focuses on the influence of cast-in-situ composite slab on "structural damage process and yield mechanism" of the composite frame of RCS. The calculation results of examples show that the cast-in-situ floor slab can increase the stiffness and flexural capacity of the beam, which makes the damage form of frame structure of RCS present a “column hinge mechanism”, and the ductility decreases a lot.By further finite element modeling, this article respectively researches the influence rules of span and thickness of the cast-in-situ floor slab on the beam rigidity of the composite frame of RCS. The results show that the beam rigidity amplification coefficient of the composite frame of RCS will exceeds the specified range of specification when the ratio of steel beams and plate thickness is larger or smaller. In addition, this article establishes the relation formula among the beam rigidity amplification coefficient of steel beams, the beam height and thickness of the concretefloor by linear regression analysis. By finite element modeling and analysis of the composite frame structure of RCS with different floors with opening, this article investigates the effect of cast-in-situ floor slab on the flexural capacity of beams of the composite frame of RCS. Based on the tensile stress equivalent principle, the reasonable value of the effective flange width of frame beams which considers the contribution of the floor is also studied. The results show that the cast-in-situ floor slab within range of six times the thickness of the floor on both sides of steel beams can be used as the calculation range of effective flange width. Moreover, the article considers the contribution of steels within the scope of flange plate to the flexural capacity of beam end and then puts forward the calculation formula of the actual flexural capacity of beam end.This article respectively adopts four kinds of structure systems(steel frame,reinforced concrete frame, composite frame of RCS, composite frame of concrete filled steel tube) for structural design on the same building and all of them can meet the seismic requirements of “three phase two level”. It also compares and analyses the seismic performance of the four kinds of frame structure. The results show that, under the premise of realizing the same using function, the seismic performance of the composite frame structure of RCS is better than that of reinforced concrete frame structure.