چكيده به لاتين
With the rapid development of railway industry in the world, as well as our country, high speed trains (HST) have attracted much attention from technical and scientific communities. One of the most important and strategic structures to be of service of railway industry are bridges. Bridges are of significant importance both in terms of technology of manufacturing and the execution costs, so that if any bridge is damaged, it is not possible to exploit that route until the bridge is repaired. For this reason, it is greatly important to study the ground-borne vibrations of such bridge classes under seismic loads, and determine the effective solutions to achieve this goal.
Recently, many seismic vibration reduction (SVR) measures are proposed in railway engineering, which are effective to reduce structural vibrations, among them are viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Tuned mass damper is the best selection among all the investigated measures to absorb vibrations subject to earthquakes from the perspective of vibration absorption performance, installation and maintenance, which its optimum tuning is related to the first-order bending mode of bridge pier.
The aim of this study is to investigate the effectiveness of TMDs in reducing the seismic response of HST bridges. Primarily, a three dimensional finite element model of bridge is established in OpenSees software. Further, a set of 60 earthquake records are selected in the three different sites, scaled by spectral acceleration intensity measure, and after considering uncertainties in bridge geometry and material properties, 60 stochastic models of bridge - earthquake are produced in two modes, with and without TMD.
Then, the random models are analyzed through incremental dynamic analysis (IDA) with factors ranging from 0.1 to 1.5, and the IDA curves are generated. On this basis, the fragility curves are developed for different bridge members in four separate limit states, and in three different site classes, with and without TMD.
According to the obtained results, the vibration response of the structure has decreased in a large degree after adding TMD, especially in the site class B. Also, since the TMD is designed and tuned according to the first-order bending mode of the bridge pier, the maximum reduction in response rate, and subsequently, the highest enhancement in the median pseudo-acceleration of the fragility curves belongs to the high piers of bridge.
