Fahad Pervaiz

Graduation Semester and Year

2022

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Michelle A Hummel

Abstract

ABSTRACT: Recent bridge failures due to hurricane-generated storm surges and riverine flood events have highlighted the vulnerability of bridge infrastructure to extreme hydrodynamic loading. In addition to posing an immediate risk to human life, bridge failures can hinder evacuation planning and emergency response efforts. Changes in flood frequency and intensity due to climate change and urbanization may alter the hydrodynamic conditions along urban streams, further stressing bridge infrastructure designed based on historical flow conditions. As a result, quantifying the structural response and stability of bridges under current and future hydrodynamic conditions is crucial to improving transportation safety and efficiency. This dissertation advances the transportation community's research needs by developing validated computational frameworks to improve the assessment of hydrodynamic impacts on bridges in riverine and coastal areas. In particular, the presented research evaluates the impacts of climate change and urbanization on bridge vulnerability to riverine flood events to support regional transportation asset management; quantifies hydrodynamic loading conditions on a range of bridge superstructures to inform the design of failure countermeasures; and develops a probabilistic framework that combines hydrodynamic modeling, structural analysis, and uncertainty quantification to improve risk assessment of coastal bridges subjected to surge and wave loading. These contributions are critical in the design and evaluation of safe and cost-effective bridge structures. The vulnerability of bridge infrastructure to riverine flood events is projected to increase due to changes in precipitation intensity and land use. Most previous assessments of changing vulnerability to high-flow events use empirical hydrologic approaches with simplifying assumptions about bridge and channel geometry. They do not model local hydraulic conditions experienced by bridges or consider spatially explicit projections of land use change. The first part of this dissertation improves upon these past studies by developing a physically-based, spatially-explicit framework to evaluate the impacts of urbanization and climate change on bridges. The framework combines future precipitation and land use projections with hydrologic and hydraulic modeling to simulate water surface elevations and velocities at stream-crossing bridges, allowing for a location-specific estimate of flow conditions. The framework is applied to bridges in Harris County, Texas, to assess the vulnerability of regional bridge infrastructure to high-flow events and to prioritize maintenance, retrofitting, and replacement efforts. The findings highlight the importance of applying hydraulic models that incorporate channel and bridge geometry, as hydrologic modeling alone cannot accurately predict impacts on bridges. Following the quantification of flow conditions (e.g., water surface elevation and velocity) at riverine bridges, formal assessment of the resulting hydrodynamic loading on bridge structures is needed to determine the potential for failure. In previous studies, the stability of bridges during flood events has been studied using scaled physical experiments and numerical modeling. However, these studies are typically limited to a constrained set of bridge geometries due to cost and time restrictions, and no studies have applied numerical simulations on full-scale bridges to investigate the scaling impacts. The second part of this dissertation applies scaled and full-scale computational fluid dynamics (CFD) modeling to calculate hydrodynamic forces on typical Texas Department of Transportation bridge superstructures and to evaluate potential scaling effects. The results allow for an assessment of how hydrodynamic loads vary with inundation depth, flow velocity, and bridge geometry and can be used to determine the resisting details necessary to ensure adequate bridge performance for flood-durable designs. Bridges located in coastal areas may be subjected to waves and surges during coastal storm events. Despite this recognized vulnerability, there is not yet a comprehensive and computationally efficient tool to evaluate hydrodynamic loading and structural response of bridges during coastal storm events while also accounting for uncertainty. The third part of this dissertation investigates surge and wave loading on coastal bridges and develops fragility curves to inform probabilistic bridge failure during hurricane events. The developed framework couples CFD modeling of hydrodynamic loading using wave conditions observed during Hurricane Ike, finite element modeling (FEM) of bridge structural response, and quantification of uncertainty in structural response based on variations in hydrodynamic conditions and material properties. The findings highlight the hydrodynamic conditions and material properties that most significantly influence bridge stability and can thus aid in determining potential bridge vulnerability during hurricane hazards. Overall, these analyses provide critical information about the flow conditions affecting bridges, the resulting hydrodynamic forces experienced by bridge structures, and the implications for bridge reliability in riverine and coastal systems. The findings of this study can be used to design bridges to withstand adverse hydrodynamic forces and overturning moments during extreme weather events, as well as to determine whether current design standards for bridges are adequate or may require improvement.

Keywords

Climate change, Urbanization, Hydrodynamic forces, Bridges, Computational fluid dynamics

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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