Study On The Influence Of Strong Motion Duration On Seismic Deformation Of High Concrete-faced Rockfill Dams

The concrete-faced rockfill dams are competitive types of dam.Due to their low investment cost,short construction period,good reliability and ease of construction,concrete-faced rockfill dams are developed at amazing speeds in terms of both their heights and their numbers in recent years.However,due to the uneven regional distribution of water resources in our country,a great number of concrete-faced rockfill dams which are in the planning or construction stages will be built in Southwest China where rich in hydraulic energy resource but prone to high-intensity earthquakes.Once these high dams destroyed as a result of earthquake action,the incalculable loss of people's lives and property will be caused.While having brought the world's people painful experiences and enormous lose,several earthquakes with serious damage since Wenchuan earthquake make people more aware that long-duration ground motions are always more destructive than short-duration ground motions and the influence of the duration of earthquake motions on the dynamic response of structures cannot be neglected.However,the importance of amplitude and frequency content has been fully considered in the current code for dam design and seismic resistance,the significance of duration has not been given as much attention,which may underestimate earthquake damage capacity and lead to catastrophic consequences.Therefore,it is of great academic value and engineering significance to carry out further study on the influence of strong motion duration on seismic deformation of high concrete-faced rockfill dams.In this study,a generalized plasticity model for rockfill materials,a plastic damage model for face slabs and a generalized interface plasticity model to describe the relative sliding behavior between the face slabs and rockfill are adopted for the nonlinear dynamic response analysis based on a 200-m-high regular concrete-faced rockfill dams.A series of as-recorded ground motions with a broad distribution of durations are selected as ground motion input.The influence of strong motion duration on seismic deformation response of high concrete-faced rockfill dams is examined comprehensively and thoroughly.The detailed works are as follows:(1)Four commonly used definitions of strong motion duration and their corresponding calculation methods are briefly introduced.Meanwhile,the advantages and problems of every definition are analyzed in detail in combination with five as-recorded ground motion records.It can provide a reference for the selection of the definition of earthquake duration when studying on the interrelationship between strong motion duration and dynamic responses and establishment of duration prediction equation.(2)Considering the individual action of horizontal component input,40 as-recorded ground motions with a broad distribution of durations modified to match a 5% damped target spectrum are selected and adjusted to two levels of 0.4 g and 0.6 g under the consideration of combining engineering practice.The effect of strong motion duration on dynamic responses of high concrete-faced rockfill dams under the action of one-component seismic input is presented.The correlation between different definitions of duration and dynamic responses of dams is analyzed and compared simultaneously.Based on the results of numerical analysis,the empirical relationship between the seismic deformation of dam and the duration of earthquake is preliminarily proposed.(3)Based on the concept of significant duration,the definition of integrated significant duration is adopted to measure the duration of multi-component seismic input.Fragility curves and probabilities of two sets of 20 spectrally equivalent as-recorded bi-directional long-duration and short-duration are determined about crest settlement ration under different earthquake intensities based on the incremental dynamic analysis method.The influence of strong motion duration on seismic response of high concrete-faced rockfill dams under the action of multi-component seismic input is investigated by comparing the vulnerability curves and failure probabilities of the dam under long-duration and short-duration ground motions.The importance of considering the duration of ground motion in seismic design and safety evaluation of high concrete-faced rockfill dams is emphasized.