Seismic Fragility Analysis Of Large-span Arch Truss Structure

The seismic fragility of the engineering structure can describe the seismic performance of the structure from a probabilistic perspective.It has become an important indicator and tool for measuring the seismic performance of structures.Taking the dry coal shed of thermal power station as the engineering background,the ground motion samples are simulated by spectral representation method.The lateral and longitudinal seismic responses of large-span arch truss structure are analyzed and its seismic fragility curves are obtained by curve fitting method of capacity demand ratio model based on damage index to evaluate the safety of the structure.First,a finite element model of a large-span arched spatial tube truss structure is established by using SAP2000 software.The dry coal shed adopts a pre-stressed arched spatial truss structure with a span of 229 m and a length of 254 m.At the same time,the dynamic characteristics of the model are analyzed to obtain the main vibration modes and corresponding vibration frequencies.After that,taking the peak acceleration of ground motion as the seismic intensity index,based on the evolutionary spectrum model of non-stationary seismic ground motions,the spectral representation method can be used to simulate the ground motion samples at different intensities.The ground motion peak acceleration is divided into 11 intensity levels,and each intensity level simulates the synthesis of 40 ground motion samples.Finally,the damage index reflecting the overall displacement of the structure is used as a response index to evaluate the seismic fragility and to divide the structural damage levels.The structural damage indicators under each ground time duration of each intensity level are calculated separately.Fitting the relationship between the structural damage index and the peak acceleration of ground motion by curve fitting method of capacity demand ratio model based on damage index,the structural fragility curves corresponding to the good slight failure,middling failure,bad failure,and collapse state are obtained.Based on this,the overall seismic performance of the engineering structure was evaluated,and the structural improvement suggestions were given.This paper has systematically studied the random ground motion responses and the seismic fragility function of the large-span arched spatial truss structure,which can provide a reference for seismic design of similar structures.