Research On ’Strong Column And Weak Beam’ By The Effect Of Cast-in-Place Floor

In recent years, huge losses of people’s life property and safety are caused by the seismic occurring frequently. In order to ensure that the cast-in-place reinforced concrete space frame structure is in the third-seismic level fortification object called no collapsing with strong earthquake, current codes put forward the design criteria named strong column-weak beam. However, the typical seismic damages manifested that reinforced concrete frame structures broke down because of weak column-strong beam which is completely contrary for current codes in the previous earthquake. Many reasons cause that the strong column-weak beam is difficult to realize, and one of the major reasons is that it is not to consider the strength increase of beam because of the existence of the floor. The seismic damages show that the cast-in-place floor and frame beam can work with synergistic effect which can increase the bending resistance of the beam. Just because of this increasing, many plastic hinges appear on the end of frame columns which much decreases the bearing capacity of the structure. Then the failure of the frame columns become the major yield and energy dissipation mechanism which serious threats the safety of the structure, even causes collapse of structure. Therefore, the effect of floor to frame beam needs to be solved. Based on the above status, this paper completed preliminarily some works such as:(1)Establish the integral reinforced concrete solid model using by solid65element which is one of the common elements in the large finite element software ANSYS, and set the nonlinear parameters.(2)Analyze the influence degree how much does the cast-in-place floor participate in the bending of the frame beam with different stiffness of the cross beam, different span of longitudinal beam, different stiffness of the longitudinal beam, different joint form and different form of the loading method under the same inter-story displacement angle.(3)Found that the conclusion in this paper is different from that of the others when studying the influence coming from the stiffness of the longitudinal beam. Therefore, change the loading method which applies the different structure with different load to ensure that all structures have the same inter-story displacement angle. Then observe the change law of the stress of the floor, and found that the law of the stress of the floor is the same with that of the first loading method.(4)According to the analysis results of the frame beam and floor, simply supported beam and floor and cantilever beam and floor, found that the effective width of the floor increases with the decreasing of the stiffness of the longitudinal beam. The effective width of the floor is different with the different beam-plates system. The effective width of the floor with the cantilever beam and floor is the maximum while the effective width of the floor with the frame beam and floor is the minimum under the same stiffness of the longitudinal beam.(4) Research on the influence law of the equivalent floor wide by the beam height in the system of the frame beam and floor, simply supported beam and floor and cantilever beam and floor. The equivalent floor wide is solved by the equivalent stiffness method.(5)Study on the influence law of the equivalent floor wide by the stiffness of straight across beam and the width of the floor in the system of the frame beam and floor.