The Vulnerability Analysis Of Roof-isolated Large-span Space Truss Structure Based On IDA

With the comprehensive development of society,the continuous progress of the level of architectural science and technology and the continuous progress of human life,the large-scale,novel structure,and advanced technology of the large-span spatial structure have broad application prospects.However,the seismic response of the space structure is complicated under earthquakes,and it will cause huge disasters and losses if damage occurs.The seismic performance of large-span spatial structures can be improved using isolation technology.The common isolation methods include base isolation and roof isolation.The roof-isolated structure is simple to apply in the design of large-span spatial structures.However,due to the higher location of the isolation layer,the influence on the substructure needs special attention in the design.In this paper,a practical project is taken as an example to study the damage mechanism and the whole process of structures under earthquake by comparing the base-isolated,roof-isolated and non-isolated large-span space truss structures.and the vulnerability of these three kinds of structures are analyzed.The main research contents are as follows:(1)Taking an actual large-span space truss structure as the research object,a finite element analysis model was established using the SAP2000 software to design base-isolatedand roof-isolated structures in the elastic stage,and the seismic responses of the two kinds of isolation structures were compared.The results show that the base shear force of the two kinds of isolated structures is reduced compared to the non-isolated structure,and the base isolation effect is better.Due to the higher position of the isolation layer,the axial force of the upper grid is reduced obviously,but the flexural span ratio is still enlarged.and the inter-storey displacement of the substructure also increases in local areas.(2)Nonlinear analysis models are established of the base-isolated,roof-isolated and non-isolated structures,and the failure rules of structures are studied under fortification intensity,rare and extremely rare earthquakes.For the upper grid structure,the results show that some members of the non-isolated structure begin to yield,very few members of the base-isolated structure begin to yield,and the members of the roof-isolated structure are in the elastic working stage under fortification intensity earthquake;Some members of the non-isolated structure fail,and the members of the roof-isolated structure and the base-isolated structure begin to yield under rare earthquake;The failure of the whole structure is caused by the failure of the hoop members of the non-isolated structure,while the failure of the roof parts of the roof-isolated structure and the base-isolated structure does not occur,and the whole structure can still continue to work under the extremely rare earthquake.For the lower frame structure,the non-isolated structure and roof-isolated structure are basically at the same performance level under different intensities earthquake(under the same earthquake),and the plastic development degree of the roof-isolated structure is higher in local areas.The plasticity of the base-isolated structure develops slowly.(3)The vulnerability of the base-isolated,roof-isolated and non-isolated structures are carried out base on IDA analysis.The results show that for the upper grid structure,the roof-isolated structure has the highest probability of surpassing each performance state,and the non-isolated and the base-isolated structures have basically the same probability of surpassing each performance state when the deflection-span ratio is used as the criterion.The probability of the roof-isolated structure surpassing each damage state is the smallest,thebase-isolated structure is in the middle,and the non-isolated structure is the largest when the yield strain is used as the criterion.For the lower concrete structure: the roof-isolated structure has the highest probability of surpassing each performance state,the non-isolated structure is in the middle,and the base-isolated structure is the smallest.(4)By comparing the vulnerability of the three kinds of structures under different intensities earthquakes,it is suggested that the lower structure should be strengthened in the design of the roof-isolated large-span space truss structure.