Study On Seismic Performance Of Steel Structure Under High Temperature Based On OPENSEES

Earthquake may usually trigger secondary fires,therefore,both seismic performance and fire resistance of building structures have been extensively studied at home and abroad,but there is little research on the seismic performance of structures at high temperatures.Once the earthquake has caused a secondary fire,the building structure will be in a high temperature state and the load-bearing capacity of the structure will be reduced,which will cause serious damage to the building if the structure is also subjected to aftershocks.By using the fiber model in OpenSees,a multi-layered steel frame is built,and different temperatures are applied to parts of this steel structure,followed by low cycle loading analysis and time history analysis to investigate the change in the seismic performance of the structure at high temperatures.In this paper,a multi-storey steel frame is established by using the fiber model in OPENSEES.Different temperatures are applied to the bottom,middle and top beams and columns of the steel structure,and then reciprocating loads（Pushover method）are applied to all nodes of these floors to carry out low cycle loading analysis.Finally,using the same model,only different temperatures are applied to the bottom beams and columns of the structure,and the TALF seismic wave is used for time history analysis to research the seismic performance of the structure under high temperatureAccording to the results obtained,the seismic performance of the structure decreases with the increase of temperature.In the low cycle loading analysi,the bottom layer is subjected to high temperature（compared to other floor subjected to high temperature）,which has an impact on the energy consumption performance of the structure.Is the largest;when the structure is subjected to a temperature within 400℃,it has little effect on the energy dissipation performance of the structure;when the temperature of the bottom beam and column exceeds 500℃,the hysteresis loop area of the hysteresis curve of the displacement and load at the loading point of the steel structure decreases with the rise of temperature,which reflects that the energy dissipation capacity of the steel structure keeps decreasing with the rise of temperature,and decreases rapidly with the increase of temperature。When the temperature of the bottom beam and column is 600 ℃,the seismic performance of the whole structure changes greatly,and the base shear force of the structure decreases,but it can still meet the requirements of the seismic design standard;However,when the temperature of the bottom beam and column is 700 ℃ and800 ℃,the overall seismic performance of the structure is seriously reduced,the base shear force of the structure is seriously reduced,the maximum inter story displacement angle of the structure becomes larger,and even exceeds the provisions of the seismic design standard.A certain layer of the structure begins to be damaged（frequently occurred earthquake）or even collapse(（rarely occurred earthquake）,which is far from meeting the requirements of the seismic design standard.