Spatial Variability of Near Field Ground Motions and Its Design Implication of Long Extended Lifeline Structures Nearby a Fault

Abstract eng:
In the near field of a fault rupture, the difference in amplitude, phase, and frequency content of ground motions over extended area, “spatial variability of ground motions”, may be quite large and has an important effect on the response of extended lifelines such as long viaduct for cars or trains and also buried pipelines for water, gas, and oil etc.. However, the spatial variability of near fault ground motions has not been characterized so far in engineering field, and hence its effect on the inelastic response of lifelines nearby a fault has not been well known. This paper presents a theoretical method of simulating deterministically the spatial variability of near field ground motions for the purpose of seismic design and analysis of extended lifelines. The near field ground motions with large permanent movements due to a fault are simulated using the stiffness matrix method and kinematical model of fault rupture in horizontally homogeneous layered half space. The effects of the spatial variation of ground motions upon the inelastic response behaviors of an extended viaduct and a buried pipeline, modeled by the fiber element method, are examined. It is found that the spatial variability of near field ground motions looks like the vortexes emerging behind an obstacle in the air or water flow. It is also revealed quantitatively that the spatial variability of ground motions strongly affect on the inelastic response behaviors of the lifelines near a fault.

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