Doctor of Philosophy (PhD)
Civil and Environmental Engineering
Global as well as local behavior of prestressed girder bridges made continuous by adding continuity diaphragms with a recently proposed positive moment continuity detail were investigated in this study. The focus of the investigation is on the positive moment caused by temperature gradients, time dependent effects such as creep and shrinkage, and some live load positions, and on the force transfer mechanisms through the diaphragm. The study utilized different approaches including analytical models for temperature evaluations and finite element models for structural assessments. Field data from a bridge using the new detail were used to validate the developed models. The temperature field of the bridge at different times of the year was estimated using an analytical method. The computed temperature profiles, actual recorded temperatures at the bridge site, and AASHTO specified design gradients are presented and compared. Primary as well as secondary thermal stresses were calculated and restraint moment caused by temperature gradient was quantified. A 3-D finite element model capable of predicting the long term behavior of prestressed girder bridges is presented. A temperature independent creep model was adopted and calibrated using early age data. Construction sequence was considered in the analysis. The FE restraint moment predictions were compared to results obtained from other commonly used analytical method. A parametric study was conducted using the analytical method to investigate the creep coefficient values. Performance of the continuity detail under live load effects was investigated. A live load test was carried out at the bridge site using two loaded trucks. A full bridge 3-D finite element model was also developed and validated with the field data. The validated FE model was also used to investigate the efficiency of the continuity detail. A more detailed 3-D FE model that zooms in on the joint was also built accounting for critical behavioral aspects of the continuity details under service conditions. Contact between cast-in-place concrete and precast concrete, transfer length of prestressing strands, and actual 180º-hook hairpin bar detail were included in the detailed model. Force transfer mechanism, stress distribution and the effective gross moment of inertia at end of girder were investigated.
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Hossain, Tanvir, "Global and local performance of prestressed girder bridges with positive moment continuity detail" (2012). LSU Doctoral Dissertations. 2.
Okeil, Ayman M.