Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Nur Yazdani

Abstract

The Federal Highway Administration (FHWA) has rated about 32% of total bridges in US as structurally deficient or functionally obsolete. One of the most frequently encountered issues for this deficiency is the impact created by cars that exceed the posted clearance for a bridge. Impact damage leads to concrete spalling or cracking, exposed or broken reinforcement/prestressing strands, global and local buckling of the structural member or piercing through the steel girder. For Example, St. Francis Bridge (North Bound) carrying St. Francis Avenue over I-30 east of downtown Dallas was impact damaged by an eighteen-wheeler carrying a heavy-duty wrecker on 29th November 2017. A part of the wrecker punched through the steel girders and piercing the concrete deck. Moreover, given the bridge's lifespan of more than 60 years, several potholes and cracks in the concrete deck were detected. To access the current performance of the bridge Non-Destructive Evaluation (NDE) was carried out along with diagnostic load test. Ground Penetrating Radar (GPR) and Impact Echo (IE) were used on the deck as a part Non-Destructive Evaluation (NDE). GPR data revealed that the top rebars cover were at greater extent than stated in the as-built drawings. On the concrete deck, IE study indicated extensive delamination. A diagnostic load test was conducted to determine the bridge's present load carrying capacity. Additionally, diagnostic load test established the presence of non-composite action. A combination of NDE and load testing was utilized to successfully load rate the bridge's girders and deck, demonstrating that both the deck and girders were unable to carry HS-20 load. Furthermore, a Finite Element Model (FEM) was prepared in ABAQUS CAE by incorporation similar geometry, materials, and boundary condition of St. Francis Bridge. The FE model was calibrated using NDE data and diagnostic load test data to capture the overall response of the bridge. Diverse retrofitting methods were investigated in the model to determine their efficacy. In addition, bridge member rating was also performed to find out the effectiveness of each proposed retrofitting options. Based on TxDOT's Average Low Bid Unit Prices, a comparative cost analysis was done for these proposed retrofitting methods, and some general recommendations were given for future investigation.

Keywords

Impact damage, NDE, Load test, Load rating, Finite element model, ABAQUS

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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