Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Civil Engineering

Advisor

Pang, Weichiang

Committee Member

Chowdhury , Mashrur

Committee Member

Putman , Bradley J.

Abstract

With the economic development in recent decades, more trucks including overweight trucks are operating on the highways. As a result, many bridges are expected to carry more loads than they did in previous years. The impact of overweight trucks on existing bridges has been an urgent concern for the South Carolina Department of Transportation (SCDOT). There is a pressing need to quantify the annual bridge cost in South Carolina caused by trucks and, in particular, overweight trucks so that the SCDOT and the state legislators can determine the appropriate fee structure for operating overweight trucks. This research focused on quantifying the annual bridge cost in South Carolina caused by trucks and especially the overweight trucks. The annual bridge cost quantified in this study included two parts: the damage cost and the maintenance cost. Since the bridge damage cost is mainly attributed to repeated loading caused by the truck traffic, the fatigue analysis was utilized to quantify the bridge damage cost.
Four Archetype bridge models were developed and used as surrogate models to represent the 9,271 bridges in South Carolina. The weigh-in-motion data, size and weight inspection violations data and SCDOT overweight truck permit data were used to develop truck models. Archetype bridges with different truck models were analyzed using a finite element (FE) software called LS-DYNA. Using the stress ranges calculated from the FE analyses, annual bridge fatigue damage was estimated and the associated annual bridge damage cost in South Carolina was computed using the bridge replacement costs.
The total asset value or replacement cost for the South Carolina bridges is approximately $9.332 billion dollars (2011 US Dollar) and the annual bridge damage cost (not including the maintenance cost) is estimated to be $29.35 million dollars (2011 US Dollar). Combined with the annual bridge maintenance cost, the total annual bridge cost in South Carolina is $35.795 million dollars (2011 US Dollar).
Based on the damage contribution and percentage of the overweight trucks in the overall truck population, the annual bridge cost allocated to the overweight trucks (including bridge damage costs and bridge maintenance cost) is found to be $8.484 million dollars.
To assist the SCDOT in establishing a new overweight permit fee structure, unit costs (cost per mile) were computed using the VMT (vehicle miles traveled) of individual truck models of different axle configurations and gross weights. It has been observed that the relationship between unit cost and gross vehicle weight is highly nonlinear.

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