%0 Journal Article
%T The Seismic Response of High-Speed Railway Bridges Subjected to Near-Fault Forward Directivity Ground Motions Using a Vehicle-Track-Bridge Element
%A Chen Ling-kun
%A Jiang Li-zhong
%A Guo Wei
%A Liu Wen-shuo
%A Zeng Zhi-ping
%A Chen Ge-wei
%J Shock and Vibration
%D 2014
%R 10.1155/2014/985602
%X Based on the Next Generation Attenuation (NGA) project ground motion library, the finite element model of the high-speed railway vehicle-bridge system is established. The model was specifically developed for such system that is subjected to near-fault ground motions. In addition, it accounted for the influence of the rail irregularities. The vehicle-track-bridge (VTB) element is presented to simulate the interaction between train and bridge, in which a train can be modeled as a series of sprung masses concentrated at the axle positions. For the short period railway bridge, the results from the case study demonstrate that directivity pulse effect tends to increase the seismic responses of the bridge compared with far-fault ground motions or nonpulse-like motions and the directivity pulse effect and high values of the vertical acceleration component can notably influence the hysteretic behaviour of piers. 1. Introduction In principle, when an earthquake fault ruptures and propagates towards a site at a speed close to the shear wave velocity, the generated waves will arrive at the site at approximately the same time. This creates the cumulative effect of almost all of the seismic energy radiation from fault and generates a ¡°distinct¡± velocity pulse within the ground motion time history, at a strike-normal direction [1]. Figure 1 portrays the three zones of directivity. The circle representing the epicenter and the black line indicates the fault. According to the model, site B (Figure 2) would experience a longer interval of the time interval between the arrivals of the waves; thus, the record at site B would have a long duration but not a velocity pulse. Intense velocity pulse usually occurs at the beginning of a record. Its occurrence is referred to as the FD effect. For more than a decade, the FD effect has been known to have potential to cause severe damage in a structure and in turn cause relatively severe elastic and inelastic responses in structures during certain periods. Figure 3 illustrates ground acceleration, velocity, and displacement time-history traces for the fault-normal component of a typical near-fault ground motion with FD (Northridge 1994 Rinaldi Receiving Station). As indicated particularly by the velocity and displacement traces, the record contains a large pulse within the time range from about 2 to 3£¿sec. To further comparison, a nonpulse record from the Northridge 1994, Century City CC North is also shown. Figure 1: Zone of directivity. Figure 2: An example of FD effect on Site A. Figure 3: Ground acceleration, velocity, and
%U http://www.hindawi.com/journals/sv/2014/985602/