Civil Engineering

 

Date of this Version

11-2011

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Interdepartmental Area of Engineering (Civil Engineering), Under the Supervision of Professors Elizabeth G. Jones and Atorod Azizinamini. Lincoln, Nebraska: November, 2011

Copyright (c) 2011 Saeed Eghtedar Doust

Abstract

The behavior of integral abutment systems and the extension of their application to curved bridges are investigated. First, the stresses in the elements of a typical integral abutment are studied by conducting nonlinear finite element analysis using the software package Abaqus. The results are design recommendations for the details of such abutments. The effect of integral abutments on the responses of bridges is also investigated. Steel and concrete bridge systems are studied separately.

The studied steel bridge systems are composed of composite I-girder superstructures and integral abutments supported on steel H-piles. A series of finite element studies for different bridge lengths and radii are conducted and the effects of several load cases on the bridges are studied. In these bridges, the stresses in the abutment piles are of critical importance from the design standpoint. The results show that horizontal curvature mitigates these stresses. The bridge movement is also studied and a procedure to find the end displacements of curved bridges is presented. Pile orientation is another significant design factor that is studied elaborately. The results indicate that, for straight bridges, the strong-axis pile bending yields lower levels of stress. A method for finding the optimum pile orientation in curved integral bridges is developed. The effect of different bearing types is also investigated. This investigation reveals the superior structural performance of elastomeric bearings compared to other bearing types.

The concrete bridge systems that are studied consist of voided slab superstructures, integral abutments and concrete drilled shafts. A matrix of finite element studies is performed for different lengths and curvatures. Similar to steel I-girder bridges, it is concluded that horizontal curvature mitigates the internal forces of the abutment elements. The orientation of the concrete shafts is also examined which again shows the advantage of strong-axis orientation. Integral abutment bridges can have flexible piers integrally connected to the superstructure to eliminate all the bridge bearings. The effect of such integral piers on the internal forces of integral abutments is also examined. In these flexible piers, moment magnification can be of crucial significance. It is shown that choosing the integral abutment system reduces the magnification effects in the slender pier columns compared to jointed bridge systems.

Advisors: Elizabeth Jones and Atorod Azizinamini

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