Effect of End Joint Gaps on Seismic Performance of Bridges

  • Ahmed Alturkmani

Student thesis: Master's Thesis

Abstract

Earthquakes are one of the most critical hazards in nature. They affect structures like bridges which are one of the most important infrastructures. Civil structural engineers tend to design bridges to have end joint gaps larger than what is required from codes like Eurocode 8-2 (or EC8-2). Joints in bridges are used for thermal expansion and contraction, concrete creep & shrinkage, and to protect bridges against seismic actions. Closure of gaps in the longitudinal direction activates the abutment-backfill systems at the bridge ends, while gap closure in the transverse direction activates shear keys. This study addresses gap closure phenomena in a typical overpass bridge, analyzed non-linearly using seismic Response History Analysis for a number of ground motions and two seismic levels, 0.16g and 0.32g which stands for the design seismic level and twice the design seismic level, respectively, with the aid of the software SAP2000. Different gaps are considered, to evaluate the effect of gap size on earthquake performance. In this thesis, the concrete bridge that will be used is the Overpass 'T7', of 99 m total length, located in Greece. The bridge consists of three-spans, pre-stressed box girder deck, monolithically connected to single circular column piers with different lengths. The deck rests on elastomeric bearings seated at the abutments with expansion joints along the longitudinal and transverse axis of the bridge. In this project, two different models will be used. The first model is to use two short piers (called: T7-short) and two long piers (called: T7-long). From the results, the reduction of gap sizes causes pier moments and shears to decrease and the abutment shears to increase. Also, Loading the abutment-backfill system after gap closure can be considered as tolerable since their large stiffness values and ultimate capacity can provide a certain level of safety combined with appropriate adjustment of gap sizes.
Date of AwardMay 2022
Original languageAmerican English

Keywords

  • Bridges
  • seismic design
  • Abutment
  • Shear keys
  • Bearings
  • Piers.

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