Seismic Fragility Analysis Of The Frame-shear Wall Structure On Steep Slopes

Mountainous cities are widely distributed all over the world.The frame-shear wall structure on steep slopes(FSWSS)with unequal height grounding characteristics is an important type of mountain building structure and is widely used in the construction of mountain towns.Due to the discontinuity of structural configuration,a sudden change of structural stiffness and mass exists in the upper ground floor of FSWSS.Thus,the FSWSS is more vulnerable to rare or mega earthquakes than the frame-shear wall structure on flat ground.At present,the seismic research on FSWSS is still at the qualitative level,which is difficult to be directly applied to the actual engineering design.It is urgent to evaluate the influence of different structural factors on the seismic performance from a quantitative perspective.Therefore,this paper studies the seismic vulnerability of FSWSS with different structural parameters.Based on the current Chinese norms,this paper designed 3 kinds of FSWSS with different shear wall layouts and two ordinary frame-shear wall structures on flat ground in seismic fortification intensity 7 degree region(0.15g).Then the seismic fragility analysis based on IDA method is carried out for these four structures.The IDA curves of these four structures and the seismic fragility curves of different limit states are investigated.The influence of different shear wall layout forms on the seismic collapse capacity of FSWSS has also been studied.The results indicate that when the number of falling layers is within the allowable range,the seismic performance of FSWSS with the shear wall evenly arranged at both ends is better than the ordinary frame-shear wall structure with the same total height,is poor than the ordinary frame-shear wall structure with the same up grounding height.The different layouts of the shear wall have a great influence on the seismic performance of the FSWSS.The seismic performance and structural collapse margin ratio of FSWSS,which the shear wall is evenly arranged at both ends or arranged in the up grounding half structure,are superior to the FSWSS with the shear wall arranged in the down grounding half structure.Secondly,this paper introduces the calculation method of the stiffness eigenvalue of FSWSS.And based on the FSWSS with the shear wall arranged in the up grounding half structure,FSWSS with different stiffness characteristics are obtained by adjusting the thickness of the shear wall and the cross-section dimensions of the beam and column.The IDA analysis of each model has been carried out by SAP2000 software,and the seismic fragility analysis of FSWSS has been carried out according to the IDA analysis results.The influence of different stiffness characteristics on the seismic collapse capacity of FSWSS has also been studied.The results show that with the decrease of stiffness eigenvalue,the probability of FSWSS reaching the limit failure state decreases,and the structural collapse margin ratio of the structure increases.The influence of stiffness eigenvalue on the seismic performance of the FSWSS is similar to that of the ordinary flat frame-shear wall structure.The research results in this paper can provide theoretical reference for the design of the FSWSS in practical engineering.