Papers by Keyword: Near-Fault Ground Motion

Abstract: The shaking table tests of a 1:7 scale model of three-floor steel frame base-isolated building was completed to study the seismic responses of base-isolated buildings under near-fault ground motions. Under the action of the typical near-fault seismic wave, the seismic responses of base-isolated structures increase with the increase of PGA. The maximum story displacements of super-structure decrease with increase of story. The velocity pulse has an adverse effect to acceleration responses of base-isolated structures. The isolation effect of base-isolated super-structures is still favorable under near-fault ground motions, but it will be necessary to add damping in isolation system or limit the displacement of bearings to prevent the excessive deformation of isolation layer.

Abstract: Near-fault ground motions are more complex than the common far field, and it can significantly change the response characteristics of the structure. The records of Taiwan chi-chi earthquake associating with velocity pulse are selected, and the seismic accelerate response spectrum of different site are studied in deep. On the basis of time-history analysis, the seismic responses of a long-span CFST (concrete-filled steel tubular) arch bridge are discussed. Weakness section of the CFST arch rib are also indicated, providing a valuable reference for aseismic design.

Abstract: This paper examined the engineering characteristics of the near-fault ground motion. The four-story reinforced concrete frame was designed under Code for seismic design of building (GB50011-2010).The SAP2000 software was applied to model it, and the nonlinear time history analyses of structure were implemented. Near-fault ground motions with forward directivity and fling-step and far field ground motions were selected as seismic inputs．The results show that in terms of some structural dynamic response parameters, such as the vertex displacement, between the corner of the layer displacement, and the base shear et al., the structural responses to the ground motion with near-fault are increased by considerable magnitudes when the seismic responses of structures step into the elastic-plastic stage, compared with far-field ground motion, and the influence of damaging the mid-lower structure is significantly greater.

Abstract: In view of huge destructibility of the near-fault ground motions, structures with long natural vibration period are liable to fall into nonlinear reaction stage. Based on a full understanding of the near-fault seismic spectrum characteristics, the out-of-plane seismic response of a long span concrete-filled steel tube (CFST) arch bridge was studied in depth, and the research result could offer a reference for near-fault aseismic design.

Abstract: From the perspective of fractal geometry, the irregularity and complexity of near-fault ground motions and seismic responses of single degree of freedom (SDOF) are analyzed. Based on the box-counting method, the fractal dimensions of 30 acceleration time series of near-fault ground motions from Taiwan Chi-Chi earthquake and California Northridge earthquake are calculated. It is indicated that the acceleration time series of ground motions present the statistical fractal property, and the influence of characteristics of near-fault ground motions on their box dimensions is remarkable. Moreover, the box dimensions of ground motions reflect their frequency property to a large extent, and can be regarded as alternative index to represent their frequency content. Finally, for the time histories of seismic dynamic responses of elastic and inelastic SDOF systems subjected to near-fault ground motions, their box dimensions are computed to examine the fractal property.

Abstract: A modified Hertz model with nonlinear damping (Hertz damp model) is proposed for capturing the seismic pounding response of adjacent structures. Relevant parameters in the model are theoretically derived and numerically verified. Then, this model is used to simulate pounding response of a base-isolated highway bridge subjected to near fault ground motions. At the same time, nonlinear viscous dampers are installed between bridge decks for pounding prevention. The appropriate damping coefficient of the dampers can be found by parametric studies. It is shown that nonlinear viscous dampers are effective in reducing the relative displacement between bridge decks. At last, the hysteresis curve, the maximal damper force and stroke are used to demonstrate the behavior of nonlinear viscous dampers. The results indicate that satisfied viscous dampers can be produced to eliminate pounding according to the current manufacturing skills.