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Seismic Performance Improvement of Bridges Using Optimized Compound Restrainers

Pahlavan Yali, Ahmad | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48659 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Joghataie, Abdolreza
  7. Abstract:
  8. During an earthquake, if the seat width provided at the joint is less than the relative joint opening, the bridge’s superstructure becomes unseat which leads to potential collapse due to the lack of support. Because of the catastrophic consequences of loss of support and the perception that the damage could easily be prevented at relatively low cost, some retrofitting programs focus on preventing such failures involved the addition of longitudinal restrainer cables and bars to limit the relative movements at expansion joints. Noticing the weaknesses of usual restrainers including the transmission of excessive forces to substructures, weak capability of energy dissipation during severe earthquakes and high dependence on ambient temperature as well as the need for decreasing the probability of damage occurrence between adjacent bridge structures due to pounding, it seems necessary to develop new models for more effective restrainers. Accordingly, this study has introduced two new restrainer devices which are called “compound restrainers”. Some simple mechanical models composed of spring-like elements with versatile characteristics have been proposed. The characteristics of these models and their force-deformation relations have been built through mathematical equations and then some nonlinear time history analyses of simple mass-spring system have been employed to evaluate the sensitivity of the compound restrainers' performance to changes in the properties of their components. Moreover, a simple nonlinear optimization algorithm was used to modify the parameters of the restrainers in order to enhance their performance. Finally some computer models of a real 2-span and a real 3-span simply supported plate girder bridges which suffer from deficiency under their current condition, have been developed. Assessing their performance, the bridges are then retrofitted by means of conventional cable restrainers as well as the compound restrainers, separately. Various nonlinear time history analyses using detailed three-dimensional models have been performed to assess the performance of the existing and retrofitted bridges during seismic excitations. In addition, a comparative study has been made between the bridges retrofitted with the compound restrainers and the bridges retrofitted with elastic and inelastic viscous dampers. The results are promising and also add to our knowledge on designing more effective restrainers for bridges
  9. Keywords:
  10. Sensitivity Analysis ; Seismic Performance ; Nonlinear Time History Analysis ; Optimization ; Seismic Behavior ; Compound Restrainers ; Multispan Bridges

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