Seismic Performance Analysis Of RC Frame Structures Considering The Effects Of Two Earthquakes

A large number of seismic records show that it is rare for a single earthquake to occur during an earthquake,and that strong earthquakes usually occur with multiple aftershocks at short intervals.If a structure is damaged by the first earthquake,the damage is often further exacerbated by the second earthquake,which may even cause the structure to collapse,resulting in serious casualties and economic losses.The current seismic codes and seismic designs at home and abroad only take into account the effects of a single earthquake,so it is of some theoretical significance and engineering value to reasonably consider the effects of multiple earthquakes on structures.To address the problem of poor seismic performance of conventional RC frame structures under two earthquakes,a specific analysis of the seismic performance and damage level of RC frame damping structures under two earthquakes were carried out using the finite element software SAP2000 modelling.The main research elements and conclusions are as follows:(1)The results of the dynamic time analysis of the RC frame structure for the first two earthquakes with multiple and rare seismic intensities show that: for the first two earthquakes with multiple seismic intensities,the traditional indicators of interlayer displacement angle,floor shear,vertex acceleration and base shear can visually highlight the damage changes of the structure;whereas for the first two earthquakes with rare seismic intensities,the traditional indicators are no longer applicable and plastic deformation indicators are required to reflect the damage changes of the structure,such as residual interlayer displacement,residual vertex displacement and the number of plastic hinges.(2)The seismic design of the original frame structure was carried out by adopting the weight coefficient method,and modal analysis and non-linear time analysis were carried out for the damping structure 1 with viscous dampers and the damping structure 2 with bucklingrestraint supports.The results show that the seismic response of the structure increases with the increase of the second earthquake intensity when the first earthquake intensity is the same;the vibration control effect of the damping structures 1 and 2 is excellent in the two first multiseismic conditions,and the energy-consuming damping effect is more obvious at lower and higher earthquake intensities respectively;the damping structures 1 and 2 can consume more than 40% of the input energy in the two first rare seismic conditions,and at the same time effectively.The reduction in the number of plastic hinges and the delay in the emergence of plastic hinges reduces the extent of structural damage under two earthquakes.(3)The overall method,the weighted combination method and the development of plastic hinges were used to assess the damage degree of the original structure and the damped structure under the action of two earthquakes.The damage indices of the damping structures 1 and 2were effectively reduced and prevented from collapsing;the results may be variable between damage assessment methods due to different parameters,but the pattern of exponential change is quite consistent.