Seismic Response And Vulnerability Analysis Of Independent Brick Hoop Caves In Northwest China

Traditional residence is one of the media of cultural inheritance in our country,which has strong historical and practical significance,and the brick hoop cave in northwest China is a characteristic residence in the loess plateau of our country,which is widely distributed in the red revolutionary district of northern Shaanxi,Shanxi,Henan and Long nan in Gansu province,and has the advantages of low cost,environmental protection,warm in winter and cool in summer.However,the structure does not take seismic measures in most fortified areas,lacks the corresponding research and design basis of seismic failure mechanism.In this paper,the seismic response of the independent brick hoop cave is analyzed,the damage quantification index of the brick hoop cave is used to analyze the earthquake vulnerability,and the design suggestions are put forward.Through the field investigation of the independent brick hoop cave in northwest China,the construction technique is summarized,and combined with the investigation data,the prototype structure of the typical three-arch independent brick hoop cave is selected,the dynamic characteristics is tested after scaling,the model is established by using ABAQUS analysis software,and the three-dimensional seismic wave is applied,The dynamic characteristics of the model structure and the tensile damage site under the earthquake are obtained,meanwhile,the stress,acceleration and tensile damage parameters of the arch,arch shoulder,arch foot and kiln leg are analyzed.The analysis results show that the failure mode of the brick hoop cave under the action of the earthquake is as follows: The edge of the side leg flashes-side across the vault sinkingthe side arches fracture-the middle leg offset-the cross-arches sinking-the structure completely destroys.The basic law of seismic response is as: the stress and acceleration response are larger than the posterior part of the cave,and the tensile damage of the side across the arches is greater than that of the middle span.In this paper,an incremental dynamic analysis method(IDA)for brick hoop cave system is introduced in detail,the vulnerability curve of the cavern model and the doublearch brick hoop cave is established by using the ratio of vertical displacement and sagittal height of the edge cross-arch as the damage quantification index of the independent brick hoop cave under the earthquake to evaluate its seismic performance.The analysis results show that under the condition of 8 degree basic intensity(200gal),the probability of minor failure of structure is about 50%,the probability of serious failure is about 10%,the probability of complete failure is less than 5%,the probability of serious damage occurs 80% around at 8 degree rare intensity(400gal),and the probability of complete failure is 37% around.Under the action of small earthquake,the double arch brick hoop cave has less probability of failure and the ductility is worse under the action of large earthquake.Combining with the tensile damage parameters and the quantitative index of the damage of the independent brick hoop cave,the damage analysis of different sagittal span ratio,middle kiln leg aspect ratio,soil cover thickness and the influence of middle leg opening and side leg form under the action of three-dimensional seismic wave of brick hoop cave is obtained,the reasonable geometrical parameters of brick hoop cave are summarized.Finally,the design suggestions for the independent brick hoop cave are as follows: The design vector span ratio of the independent brick hoop is 5/12 and above,the middle leg aspect ratio is 2.43 and below,the upper overburden thickness is about1.0m,the middle leg opening rate should not exceed 35%,and the side leg adopts solid kiln leg is more favorable to the seismic resistance of the structure.