Seismic Resilience Assessment Of Concrete-Filled Steel Tube Transmission Tower

As an important carrier of power transmission,it is of great social significance and economic value to ensure the safety and normal operation of transmission tower.In recent years,with the development of large-span and ultra-high voltage transmission networks,concrete-filled steel tube(CFST)transmission tower structures have been widely used because of their ductility,high bearing capacity and superior wind resistance,etc.,while the characteristics of high tower height and large span also make the transmission towers more susceptible to earthquake.Therefore,in order to ensure the safe operation of the transmission towers under earthquake,It is necessary to evaluate its seismic performance.Since resilience was proposed,resilience assessment has been widely used in all walks of life,such as community resilience assessment.lifeline system resilience assessment,enterprise resilience assessment,etc.However,the current performance assessment of transmission towers mainly focuses on evaluation methods and how to enhance the resilience level,and there are few relevant studies on earthquake resilience assessment of transmission towers.Based on this background,Based on FEMA P-58 and Evaluation Standard for Seismic Performance of Buildings,this paper proposes an evaluation method for seismic performance of concrete-filled steel tube(CFST)transmission tower and evaluates its seismic performance grade.The main contents are as follows:(1)The seismic resilience evaluation theory of transmission tower is proposed,and its main contents are:1)Determine the relevant information of transmission tower.Including the height,the number of layers,repair time,repair costs,etc.;2)Establishment of transmission tower model and analysis of elastoplastic time history;3)Extraction of engineering demand parameters;4)Determine the damage state of all components contained in the transmission tower.According to the engineering requirement parameters,combined with the vulnerability database of structural/non-structural components,the damage state of all components contained in the transmission tower is determined;5)To evaluate the repair time and cost indexes of transmission towers under the action of four earthquake intensities:frequent,fortification,rare and extremely rare;6)Comprehensive seismic resilience grade evaluation for transmission towers.(2)IDA method is used to carry out elastic-plastic time history analysis and vulnerability analysis of CFST,and draw the vulnerability curve of the transmission tower in the case of frequent,fortify,rare and extremely rare earthquakes.The influence of the first period spectral acceleration of the earthquake on the failure probability of the CFST is quantitatively analyzed.Due to the interaction between concrete and steel tube,the seismic vulnerability of concrete transmission tower is different from that of ordinary concrete transmission tower.In order to compare and study the difference of their seismic vulnerability,this paper compares the analysis results of the seismic vulnerability of CFST with that of ordinary transmission tower.(3)The rating standards for the maintenance cost,maintenance time and comprehensive performance of the transmission tower are defined.The evaluation method based on strength is adopted to evaluate the concrete-filled steel tube transmission tower under four seismic intensity levels of frequent occurrence,fortification,rare occurrence and extremely rare occurrence.The evaluation result is a performance curve,which is a function of the specific value of the specific performance index and the probability of being less than the value.This paper focuses on the concrete performance of concrete-filled steel tube transmission towers under the two performance indexes of maintenance cost and maintenance time under the vibration intensity of different places and analyzes the specific performance of the performance points corresponding to the structure at P=84%,which is the best estimated value selected according to Standard for seismic resilience assessment of buildings recommendations,and then the maintenance cost,maintenance time and comprehensive toughness rating results of concrete-filled steel tube transmission tower under four seismic intensity levels are obtained...