Effect Of Cast-in-place Floor On Seismic Response And Yield Mechanism Of RC Frame Structure

Reinforced concrete frame structure has the advantages of flexible layout,large space and good seismic performance under reasonable design conditions.It is widely used in office buildings,teaching buildings and multi-storey buildings.However,in recent years,many RC frame structures designed according to the code failed to show the design expectation,such as the yield mechanism of "strong beam and weak column",the earthquake damage is more serious.There are many factors that affect the seismic response and yield mechanism of RC frame structure,and cast-in-place floor is one of the most important factors.At present,scholars at home and abroad have done some research on the effect of cast-in-place floor slab on seismic behavior of RC frame structure,but there is still room for further research on the quantitative study of seismic response and yield mechanism of RC frame structure.In this paper,the influence of floor thickness and span on floor displacement,shear force and overall stiffness of frame structure is studied by means of elastic time history analysis based on ETABS and elastic-plastic time analysis based on PERFORM-3D.And the influence on the yield mechanism of frame structure.The main conclusions are as follows:(1)with the existence of cast-in-place floor slab,the natural vibration period of frame structure decreases,the lateral stiffness and interstory shear force increase,but the elastic floor displacement increases,and with the increase of floor thickness,the elastic floor displacement increases.The main consideration is that the cast-in-place floor increases the overall stiffness and mass of the structure,and the seismic action of the structure increases;(2)with the increase of floor span,the overall stiffness of the frame decreases and the overall force of the structure decreases,so the floor displacement,the interstory displacement angle and the story shear force decrease accordingly;(3)the existence of cast-in-place floor makes the frame structure in the elastic-plastic stage,resulting in different positions of the maximum interstory shear force under the same seismic intensity;(4)With the existence of cast-in-place floor slab,the bending moment at the end of the frame beam decreases,and with the increase of floor thickness,the bending moment value of the beam shows a decreasing trend,mainly because the in-situ floor slab shares the internal force of the frame beam;(5)The steel bars parallel to the beam in the floor will participate in the bending of the beam,which makes the flexural capacity of the beam increase greatly.