Analysis Of Ground Motion Characteristics Based On Energy And Evaluation Of Collapse Resistance Of Frame Structure

In this paper,PGV/PGA>0.2s,magnitude Mw>6.5 and epicentral distance D were selected as the principle of pulse-like ground motion.20 near-fault pulse-like and medium-far field pulse-like ground motion records were selected,and 20 ATC recommended near-field pulse-like,near-field no pulse and far-field ground motion records were chosen respectively.The ground motion characteristics based on energy analysis were investigated.Four short,medium-long and long period SDOF system models based on bilinear hysteresis model were established to analyze the energy response characteristics of each system under ground motion excitation.Secondly,the 4-story and 9-story frame structures were established,and the influence of the selection of ground motion on the evaluation of the collapse resistance of the structures was discussed.The following conclusions were obtained:(1)The spectral value of the mean energy spectrum of ATC near-field no-pulse ground motion is larger in the short period range(0.005~1.10s);the near-fault pulsetype has larger spectral value in the medium-long period(1.10~4.55s);in the long period range(4.55~6s),the spectral value of the mid-far field pulse-type ground motion is the largest;in the period of 0.41~1.80 s,the near-fault pulse hysteresis energy spectral value is the largest;in the interval of 1.80~6.00 s,the mid-far field pulse spectral value is much larger than the rest of the ground motions.(2)The release energy rate of near-fault pulse ground motion is the fastest;the farfield ground motion comes next;the energy release rate of the mid-far field pulse-type is the slowest;there is no significant difference in the energy release rate between the two types of ATC near field ground motion.(3)The short-period system tends to have the cumulative damage destruction mode under the action of ground motion;the medium-long period system tends to accumulate damage mode under the action of medium-far field pulse-type ground motion,and the system is prone to appears the first destruction mode that exceeds the maximum displacement limit under the action of the remaining ground motion.(4)The ratio of the maximum instantaneous input energy to the total input energy of the short,medium-long and long period systems is negatively correlated with the energy release rate of the ground motion;the proportion of kinetic energy and hysteretic energy in the total input energy of the medium-long and long period system has negative correlation and positive correlation with the energy release rate of the ground motion respectively;the maximum kinetic energy of the system has an important influence on the maximum displacement response,both are positively correlated.(5)The selection of ground motion has a significant impact on the evaluation of the collapse resistance of multi-story frame structures: the 4-story frame structure has relatively weak anti-collapse resistance under the action of the near-fault pulse-type,ATC near-field no-pulse and medium-far field pulse-type ground motion,and has the strongest anti-collapse resistance under the action of the ATC near-filed plus-type ground motion;the 9-story frame structure reaches the collapse state more rapidly under the action of the mid-far field pulse-type ground motion,and reaches the collapse state quickly under the near-fault pulse-type ground motion,while three types of ground motions recommended by ATC have relatively weak destructive effects on medium-long period structures.(6)The seismic vulnerability analysis is consistent with the analysis results of energy-based ground motion characteristics,indicating that the PGV/PGA>0.2,epicentre distance D and magnitude Mw as the recognition conditions of the pulse horizontal ground motion have certain rationality.