Study On The Influnce Of Ground Motion Characteristic To Total Input Energy Spectrum Of MDOF System

Energy response analysis of structure under the action of earthquake is mainly effected by two factors. The first one is structural dynamic characteristics while the second one is characteristics of ground motion. In this paper, a comprehensive study on the influence of the three essential factors of ground motion to the total input energy spectrum of elastic and elastroplastic multi-degree of freedom(MDOF) system was carried out.. The main work and conclusions are shown as follows:1. Seismic waves' s selection and groupingBased on the seismic waves and corresponding waves selection procedure based on response spectrum provided by PEER website and through the way of the Secondary –dispatching Full Frequency Donmains waves selection, 11 groups, each of which consists of 10 seismic waves, were picked out for further research. And it's proved that the fourier spectral mean period(mT) is reasonalbe as the measure index of seismic spectral components.2. The theoretical derivation and MATLAB programming for total input energyspectrum of MDOF system.Based on the input energy incremental formula for SDOF system, the input energy incremental formula for MDOF system was deduced in this paper. And the calculation program of the total input energy time history and input energy spectrum curve of MDOF system is worked out.3. Through analysing influence of he three essential factors of ground motion to the input energy spectrum of elastic and elastroplastic MDOF system. With verification of enhanced sample capacity, main conclusions were as follows:(1) Influence of seismic amplitudeFor MDOF system, whose input energy spectrum is proportional to the power of kof PGA.The value of k equals to 2 for elastic MDOF system while k equals to 1.64~1.91 for elastroplastic MDOF system.(2) Influence of seismic spectral componentsWith the increase of proportion of long-period waves in seismic waves, the value of input energy spectrum is increased. Meanwhile, peak value of input energy spectrum moves towards long period direction.(3) Influence of seismic durationWith the increase of 70% significant duration, corresponding value of total input energy and input energy spectrum grows. When the value of 70% significant duration is less than 10 seconds, the input energy spectrum is not sensitive to hard site categories while sensitive to soft site categories.