Year of Publication

2005

Degree Name

Doctor of Philosophy (PhD)

Document Type

Dissertation

College

Engineering

Department

Civil Engineering

First Advisor

Dr. Issam E. Harik

Abstract

The current design code governing bridge structure resistance to vessel impact loads in the U.S. is the American Association of State Highway and Transportation Officials' (AASHTO) Guide Specification and Commentary for Vessel Collision Design of Highway Bridges. The code stipulated method, based on Meir-Dornberg's equivalent static load method, is usually not warranted because of insufficient data on the impact load histories and wide scatter of the impact force values. The AASHTO load equations ignore certain fundamental factors that affect the determination of impact forces and bridge dynamic responses. Some examples of factors that are omitted during standard impact force analysis are: impact duration, pier geometry, barge-barge and barge-pier interactions, and structural characteristics of bridges.

The purpose of this research is to develop new methods and models for predicting barge impact forces on piers. In order to generate research information and produce more realistic flotilla impact data, extensive finite element simulations are conducted. A set of regression formulas to calculate the impact force and time duration are derived from the simulation results. Also, a parametric study is performed systematically to reveal the dynamic features of barge-bridge collisions. A method to determine the quasi upper bound of the average impact force under any given scenarios is preposed. Based on the upper bounds of the average impact forces, an impact spectrum procedure to determine the dynamic response of piers is developed. These analytical techniques transform the complex dynamics of barge-pier impact into simple problems that can be solved through hand calculations or design charts. Furthermore, the dependency of the impact forces on barge-barge and barge-pier interactions are discussed in detail. An elastoplastic model for the analysis of multi-barge flotillas impacting on bridge piers is presented. The barge flotilla impact model generates impact force time-histories for various simulation cases in a matter of minutes. The results from the proposed model are compatible with the respective impact time-histories produced by an exhuaustive finite element simulation.

All of the proposed methods and loading functions in this study are illustrated through design examples. Accordingly, the research results may help engineers to enhance bridge resistance to barge impacts and also lead to economic savings in bridge protection design.

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