Seismic Fragility Analysis Of Multi-Storey Frame Structure Considering The Effect Of Valley Terrain And Oblique Incidence Of Seismic Waves

In view of the special situation of extensive distribution of the terrain in the Silting-Valley in the Hangjiahu region,combined with the local soil engineering characteristics and the status quo of seismic fortification zones,considering the soil-structure dynamic interaction,based on dynamic time history analysis and probability statistical methods.Earthquake fragility curves for multi-story frame structures applicable to the Hangjiahu region are given.The dynamic response and fragility of the multi-story frame structure under the vertical incidence of seismic waves without consideration of the foundation,the homogeneous foundation and the local valley foundation were compared.Moreover,the differences in the seismic response of the house structure at different positions in the valley were particularly examined.In addition,based on the elastic wave theory,the equivalent boundary load calculation formulae for oblique incident seismic waves is deduced for the infinite boundary,and the dynamic response differences and fragility of multi-story frame structures at different incident angles of seismic waves are further studied.The main conclusions of the paper include:(1)Without considering the soil-structure dynamic interaction,the horizontal displacement of the housing structure will be underestimated,and the corresponding fragility performance level exceeds the probability that the probability is low,and the result will be dangerous;Considering the soil-junction interaction.the maximum displacement between the layers occurs from the high level to the first layer.This deformation law is closer to the actual investigation of the earthquake damage phenomenon(2)The focusing effect produced by the terrain of the valley will generate vertical seismic acceleration components in the foundation,which will amplify the horizontal acceleration at the bottom of the column structure,cause vertical displacement of the structure,and increase the horizontal displacement,maximum displacement between layers,and internal forces of the structure.Thereby increasing the surpassing probability of the corresponding performance level;The dynamic responses of the structures at different positions in the valley are different.In the conditions studied in this paper,the closer the structure of the house is to the center of the valley,the greater the horizontal displacement and the greater the increase in the probability of surpassing the corresponding performance level.The maximum increase is 12.1%(3)The seismic angle of the seismic wave has a non-negligible impact on the seismic response of the structure.Taking oblique incidence of SV wave as an example,the structure of the house shows obvious stress asymmetry under the influence of oblique incident seismic waves.The shear force near the source side are large away from the source side;Under the condition that the energy input is consistent,the horizontal acceleration and horizontal displacement of the structure appear to decrease first and then increase with the increase of the incident angle of the seismic wave,and the vertical displacement and vertical acceleration of the structure increase with the incident angle.The performance level of the frame structure exceeds the probability with the increase of the incident angle,which first decreases and then increases.In the four angles studied in this paper(vertical incidence is regarded as ?=0°),the smallest surpassing probability is 300 when the incident angle is 20°.The probability is greatest.Under the influence of seismic wave oblique incidence,homogeneous foundation model maximum probability increase 13.6%,valley foundation model maximum probability increase 14.0%,it is can be concluded that when local valley terrain exist in the foundation,the influence of seismic wave oblique incidence on the structural fragility is more significant.