On Significant Duration Of Records From NGA Strong Ground Motion Database

The seismic input is of great theoretical and practical significance to the seismic fortification of buildings and engineering sites.Duration has a significant effect on the nonlinear seismic response of structures aengineering sites,but there are less studies on the duration of ground motion than on the amplitude and frequency spectrum.In this paper,based on the research status of duration in domestic and foreign places,the factors affecting the significant duration are studied,and the characteristics of the self-definition of significant duration are discussed.The NGA significant duration prediction model is given to provide a reference for the estimation of significant duration in similar geological tectonic areas.The main tasks of the thesis are as follows:Firstly,the definition of significant duration and bracket duration,as well as the factors affecting the duration are introduced,the concepts of baseline correction and band-pass filtering used in the processing process are expounded,and the technical process of data processing is given.Secondly,the data source was explained,and 5-95% significant duration and bracket duration were calculated.The significant duration difference between the two components was compared,indicating that p-wave energy and amplitude had a great influence on the calculation results of significant duration.Furthermore,the variation of significant duration with magnitude and distance is analyzed,and compared with the variation of brackett duration.It is found that the significant duration advantage lies in the consideration of the energy distribution of the whole record,but the defect lies in the inadequate consideration of the absolute magnitude of the amplitude.The characteristic of bracket duration is that it has good stability at a distance,but the weakness is that the selection of threshold is too subjective.The variation of significant duration with magnitude and faults distance was calculated,significant duration is closely related to the slope of Arias intensity curve and the recorded overall length,but not closely related to the absolute magnitude of amplitude.With the help of the multiple nonlinear regression method considering the random effect,the NGA-East and NGA-West2 significant duration prediction models are given respectively,and the error analysis shows the stability of the regression results.The significant duration predicted values of both models increased with the increase of magnitude and fault distance.In addition,with the same magnitude and fault distance,NGA-East gave a larger estimation than NGA-West2 model.By comparing the NGA-West2 model with the existing significant duration prediction model,it is found that the model in this paper is not significantly larger or smaller,which confirms the reliability of the regression results in this paper.