Effect Of Cast-in-place Floor Slab On Seismic Behavior Of Concrete Frame Structures

The “strong-column-weak-beam” is a seismic design method proposed to ensure the ductility of the concrete frame structure.However,in the actual earthquake disaster,it is rare to see the expected beam hinge yield mechanism of the concrete frame structure,and more plastic hinges appear on the frame column.Among them,the synergy between the cast-in-place floor slab and the frame beam is one of the main factors affecting the realization of the RC frame structure "strong column wea k beam".In this paper,the main research object of cast-in-place floor slab is as follows.The main contents of seismic analysis of reinforced concrete frame structure are as follows:(1)Using the Pushover analysis method and the dynamic elastoplastic ti me history analysis method,a 3×2 RC frame structure with a height of 4 layers is analyzed,and the entire slab frame is constructed,the slab frame is not provided,and the floor slab is 6 times thick.The three sets of flanges were compared and analyzed under different column bending moment increasing factors.The analysis results show that the expected strong column weak beam failure mechanism can not occur when the column bending moment increase coefficient is 1.7;and the axial compression ratio of the frame column has an important influence on the yield mechanism of the frame structure;6 times plate thickness,and the equivalent conditions of the cast-in-slab model are for further study.(2)Pushover analysis of RC frame structure by changing the thic kness of cast-in-place floor slab explore the seismic performance of the structure.Comparative analysis of the Pushover capacity curves,structural displacement and corresponding plastic hinge development law of each model can be obtained: small increase in floor thickness it does not affect the initial stiffness of the structure,the structural bearing capacity,the structural displacement,the plastic hinge distribution and the hinge sequence.Further increasing the thickness of the cast-in-place floor slab will not only improve the structural load-bearing capacity,but also reduce the number of structural column hinges and reduce the structural lateral displacement.The specific impact of the value and plate thickness needs further analysis.(3)Considering the influence of the floor on the seismic performance of the frame structure by changing the size of the live load,analyzing the Pushover capacity curve,structural displacement and corresponding plastic hinge development law of each model can be obtained: the initial stiffness of the structure with the increase of the live load It has declined,but it has little effect on structural displacement and plastic hinge development.(4)Establishing a model with cast-in-place floor slabs,considering the impact on the seismic performance of the frame structure by changing the span,and analyze the Pushover capacity curves,structural displacement and corresponding plastic hinge development law of each model: the increase of span makes the structure The initia l stiffness and structural displacement value decrease,while the number of structural column hinges decreases,the beam hinge increases,and the structural failure mode is improved,which is conducive to the expected strong beam weak beam failure mechanism.(5)Using the Pushover analysis method,SAP2000 modeling analysis is carried out in four different ways of considering the slab.The analysis results show that the relative positional relationship between the beam and the slab should be correctly considered in the structural simulation analysis.The elastic shell element model agrees well with the Pushover capacity curve s of the layered shell element model.Th e lateral displacement values are similar,the development of plastic hinges and the degree of structural damage are basically the same.In the actual project,the elastic shell structure can be used to simulate RC concrete structure,which can satisfy the analysis.Accuracy requirements,improve the speed of the solution.