Thesis - Open Access
Master of Science (MS)
Civil and Environmental Engineering
Condition Factor, Double-Tee Bridges, Field testing, Load Rating, Rating Factor, Strength Testing
The most common type of bridge on South Dakota (SD) local roads is precast prestressed double-tee (DT) girders. More than 700 DT bridges are currently in-service in SD. Structural detailing, aging, traffic volume, and environmental conditions affect the structural performance, integrity, and capacity of DT bridges. When a bridge is affected by one or more of the aforementioned parameters, the estimation of the bridge safe live loads is necessary to ensure the safety of the traveling public and to prevent excessive bridge damage and collapse. Load rating of damaged bridges is challenging mainly because of a lack of information regarding the capacity and live load distribution of damaged components. In the present study, quantitative definitions were proposed to identify all damage types and condition states specific to double-tee girders. Subsequently, more than 350 inspection reports specific to SD double-tee girder bridges as well as the SD Bridge Management Database were reviewed to determine the frequency of damage types and condition states, bridge span length, bridge number of spans, girder depth, and bridge skew conditions. The statistical database was then used to identify double-tee bridge candidates for field and strength testing. Ten double-tee bridges were found as initial candidates for field testing and they were inspected for further evaluations. Subsequently, two bridges were selected for field testing. Girder distribution factors (GDFs) and dynamic load allowance (IM) were measured. The field test results showed that the AASHTO LRFD specifications can be used to estimate the moment and shear GDFs for SD doubletee girder bridges with a longitudinal joint damage of condition state 3 or less. For the calculation of moment and shear GDFs for a SD double-tee girder bridge with a longitudinal joint damage of condition state 4, GDFs are the greater of (a) the factor for the exterior girders, (b) the factor for the interior girders, and (c) 0.6. Furthermore, the AASHTO LRFD can be used for the estimation of IM for damaged double-tee girders. Accurate estimation of the capacity of a damaged double-tee girder is crucial in this project for a safe load rating. To verify the available moment and shear capacity estimation methods, two 45-year old double-tee girders, one 50-ft (15.24-m) long and another 30-ft (9.14-m) long, were extracted from a bridge located in Nemo Road, SD, and were strength tested at the Lohr Structures Laboratory at South Dakota State University. A four-point loading configuration was selected for the strength testing. The verified methods were then utilized to calculate the shear and moment capacities of 23 different double-tee sections, which are common in SD. Based on the statistical, experimental, and analytical studies, a methodology was proposed for damaged double-tee bridges in which the load rating may be performed similarly to the LRFR method that currently used in practice. Nevertheless, it is recommended to modify the capacity (C) and live load components (LL and IM) of the load rating equation accounting for different damage types and condition states.
Includes bibliographical references
Number of Pages
South Dakota State University
In Copyright - Non-Commercial Use Permitted
Rimal, Sandip, "Methodology for Load Rating Double-Tee Bridges" (2018). Electronic Theses and Dissertations. 2964.