Access Type

Open Access Thesis

Date of Award

January 2018

Degree Type

Thesis

Degree Name

M.S.

Department

Civil and Environmental Engineering

First Advisor

Fatmir Menkulasi

Abstract

Short to medium span composite bridges constructed with adjacent precast inverted T-beams and cast-in-place topping are intended to provide more resiliency against reflective cracking and time dependent effects compared to voided slabs and adjacent box girder systems. This thesis investigates the stresses in the end zones of such a uniquely shaped precast element. The transfer of prestressing force creates vertical and horizontal tensile stresses in the end zones of the girder. A series of 3-D finite element analyses were performed to investigate the magnitude of these tensile stresses. Hoyer effect is captured by modelling the strands as solid elements and defining the interaction between strands and concrete in the tangential and normal behavior using friction coefficient and hard contact, respectively. The modelling protocol captures spalling, splitting, and bursting stresses. It was found that, stresses in the end zones of precast inverted T-beams with tapered webs are not likely to cause any significant cracking if the beam is reinforced based on AASHTO’s provisions for pretensioned anchorage zones. Various modeling techniques were evaluated, and it was found that linear elastic models with truss elements are adequate for design purposes in terms of mapping where the end zone reinforcing needs to be located. However, if such modeling capabilities are not available AASHTO’s provisions suffice in terms of reinforcing the critical areas in the end zones.

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