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Structural Engineering and Mechanics
  Volume 64, Number 2, October25 2017, pages 213-223

Fragility curves for the typical multi-span simply supported bridges in northern Pakistan
Muhammad Waseem and Enrico Spacone

    Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with nonlinear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.
Key Words
    concrete bridges; fragility curves; non-linear dynamic analysis; incremental dynamic analysis; Pakistan
Muhammad Waseem: National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
Enrico Spacone: Department of Engineering and Geology, University of Chieti-Pescara, Viale Pindero, 42, 65127, Pescara, Italy

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