Study On Influence Of The Site Excavation On Earthquake Action Of Building Structure With Basement

The seismic behaviors of building structures with basement changes due to site excavation. Little consideration was given to the influence of site excavaion on the seismic behaviors and no specification on the seismic wave input of underground structures is presented in the current building code. So the influence of site excavation on the seismic behaviors of buildings with basements is worhthy to study.Centered on the influence of site excavation on the seismic behaviors of buildings with basements, the main work is concluded as following: the influence of site excavation on the seismic response is considered with program ANSYS(a finite element program); comparison between the response of site excavation and free site; giving assessment on the seicmic response caused by site excavation; seismic response analysis of buildings with basement considering the influence of site excavation; initial determination the earthquake action of building structural with basement.The major conclusions are summarized as following:1. The maximum value of spectrum including the effect of site excavation on different site conditions should determine according to different site conditions.2. The soil stiffness gradually become harden along the depth, while the peak acceleration along the foundation pit become less gradually with linear. The peak acceleration on the top foundation is 1~6 times than that at the bottom of the foundation.3. The influence of site excavation on the structural seismic response: a. when the structures isolate from the peripheral soil, the inner force is less than the same structure which locates on the free field. The softer the soil layers, the less the inner force and on some special condition, the inner force on some local stories increases; b: when the structures adjoin the peripheral soil, the inner force of most components is less than the same structure which locates on the free field and the properties of layer and the seismic wave input have great effect on the inner force.4. In the practical project design, to typeâ…¡site the thichness of covering layer after the site excavated not belongs to the specificaion of type I site and to typeâ…¢site the thichness of covering layer after the site excavated not belongs to the specificaion of typeâ…¡site, the earthquake action of the building with basement is determined by the original site classification.5. The building with basement which located on the typeâ…¡site , the thichness of covering layer after the site excavated meets the specificaion of type I site according to the current building code, it assumes as seismic response of type I site when the depth excavating is deep; the site classfication can be modified to determine the seismic wave input of buildings with basements; The constructional measures of structures is taken with no modification due to the complxity of constructional measures of structures.6. To typeâ…¡site of which the thichness of covering layer(ChongQing region) is thin, it can be modified as type I site to consider the influence of site excavation on the decresing of earthquake action when the upper structure is located on the basement rock directly after site excavation.