Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Vijaya K. A. Gopu

Abstract

A rigorous and efficient analytical model to predict the long-term deformation behavior of bridges with multiple, precast, pretensioned, prestressed concrete girders supporting cast-in-place-concrete deck slabs, was developed. The analytical procedure uses the finite element method with three-dimensional 20-node isoparametric elements to realistically model bridge geometry. Time dependent effects due to load and temperature history, creep, shrinkage and aging of concrete are included in the analysis. Creep and shrinkage strains are evaluated at different times using the more commonly used procedures, namely, the ACI-209, Bazant-Panula II and CEB-FIP procedures. Temperature strains are calculated from an assumed typical bridge temperature distribution based on the average temperature occurring during any time period. The effect of temperature on creep is also accounted for. Prestressing tendons are modelled as being embedded in concrete and as contributing to girder stiffness. Position continuity in tendon profiles is maintained. Losses in prestress due to steel relaxation and geometry changes are calculated in the analysis. The analytical model is capable of simulating typical construction schedules to predict deformations at any stage during the service life of a bridge. A parametric study was conducted to quantify the influence of key geometric and material properties of the bridge on the long-term expansion joint movements. Bridge systems representing a wide range of key parameters were analyzed to develop formulas to estimate creep and shrinkage movements with a certain degree of confidence. These formulas formed the basis of a rational procedure for calculating the long-term bridge deck movements. The recommended procedure accounts for the effects of bridge geometry and material properties on joint movements. These effects are ignored in current highway bridge deck joint design methodology. The use of the recommended procedure permits the designer to determine span lengths and the maximum number of continuous spans between expansion joints in bridge decks, if the limit of movement that can be accomodated by the chosen joint sealing system is known. The analytical model has been coded into a FORTRAN program which can be used to evaluate the long-term behavior of bridges with or without expansion joints, and with different support conditions.

Pages

315

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