Study On Dynamic Behavior And Design Method Of High-rise Structures Under Multi-type Long-period Ground Motions

Far-field harmonic ground motions, near-fault forward-directivity ground motionsand near-fault fling-step-type ground motions all belong to long-period ground motions.Earthquake disasters of Wenchuan and East Japan indicates that these kinds of groundmotions have great destructive effects on long-period structures. The current seismiccode can’t ensure the security of long-period structures because it has not consideredthe long-period ground motions. This paper organizes analysis around three kinds oflong-period ground motions from the characteristics of ground motions, dynamicresponse characteristics and damage failure mechanism of high-rise structures andstructural seismic design method. The main contents are as follows:(1) Comparative analysis of characteristics for three kinds of long-period groundmotions are made. Contrast the peak values, ratio of peak values, duration andresponse spectrum. Based on Hilbert-Huang Transform, the concept of accumulatedenergy spectrum, strong frequency band, and time distribution coefficient of energywere proposed to explore the low frequency characteristic, broad frequency bandcharacteristic and pulse characteristic from the perspective of energy time-frequencydistribution of ground motions.(2) Design and establish finite element modes for frame structures and frame-shear wall structures which can represent short, medium and long period structures.21long-period ground motions and3ordinary ground motions are selected as the excitingforce to make96times elastic-plastic time-history response analysis, so as to acquiredynamic response characteristics of high-rise structures under long-period groundmotions. Meanwhile, time-frequency characteristics of displacement response forhigh-rise frame structure and frame-shear wall structure are analyzed based onHilbert-Huang Transform, so as to further explore response characteristics of high-risestructures under long-period ground motions.(3) Analyze the influence of pulse parameters on dynamic response for high-rise structures. Firstly, propose pulse parameter identification method based on EMD forlong-period ground motions, which can recognize the pulse peak velocity, pulse periodand pulse duration. Then, establish simplified equivalent models for three kinds oflong-period ground motions and validate the rationality of the models throughcomparative analysis. Finally, based on19times elastic-plastic time-history analysis,analyze the influence laws of pulse period and pulse duration of long-period groundmotions on elastic-plastic earthquake response for one12story frame structure.(4) Analyze the damage failure mechanism of high-rise structures underlong-period ground motions. Firstly, analyze the correlation between the maximumtransient input energy of long-period ground motions and the maximum elastic-plasticdisplacement of SDOF. On this basis, the concept of transient input energy ratio isproposed and it is used to analyze the failure modes of high-rise structures under threekinds of long-period ground motions. Then, based on the proposed damage analysismethod named “Step-by-step Damaged Analysis”, comparative analysis of the damageevolution characteristics of high-rise structures under long-period ground motions ismade based on54times elastic-plastic time-history analysis. Finally, based onEmpirical Mode Decomposition (EMD), the controlled IMF of long-period groundmotions for the nonlinear earthquake response is analyzed. Propose the concept ofvalid long-period ground motion and define the valid peak and valid peak ratio. On thisbasis, reveal the resonance reaction mechanism of high-rise structures underlong-period ground motions. Meanwhile, propose the concept of energy gradient andanalyze the distribution law of energy gradient for three kinds of long-period groundmotions. On this basis, reveal the pulse reaction mechanism of long-period groundmotions for high-rise structures.(5) Analyze the structural seismic design method considering long-period groundmotions. Discuss the problems of current seismic code including the intensity, designground motion parameters, design earthquake group and time-history analysis. Basedon100long-period motions, establish400elastic-plastic SDOF, analyze and proposethe seismic strength index of long-period ground motions. Comparative analysis ofChinese, American, Japanese and European seismic design spectrum are made toexplore the applicability of the considering for long-period ground motions. Analyzefrequency spectrum characteristic periods and frequency non-stationarity oflong-period ground motions so as to provide research foundation for seismic hazardanalysis. Discuss the division methods of structural period and analyze the feasibilityof the division method based on transient effects of ground motions. Finally, propose structural seismic design suggestion considering long-period ground motions.