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theses

For bridge evaluation, the load rating factor is the indicator that assesses the current load carrying capacity of a structure. To calculate the rating factors (RFs), the geometries and condition of a bridge are needed. For those bridges that are old and have no available plans, a methodology is needed to estimate the accurate rating factors and give guidance for future assessment and inspection. The objective of this study is to develop a guideline to load rate the prestressed concrete (P/C) girder bridges when the as-built plans are not available for New Jersey Department of Transportation (NJDOT). The guideline includes data collection, use of nondestructive testing/evaluation (NDT/E) and load tests, as well as a proposed approach to estimate the as-built design. To validate the proposed approach of estimation, nine (9) simply-supported P/C girder bridges with known plans were selected by NJDOT in this study. The diagnostic load test and recommended NDT/E were performed on a simply supported P/C I-girder bridge located on I-80 Eastbound over Mount Hope Mineral Railroad. A 3-axles Class 6 truck, with a gross vehicle weight (GVW) of 54.7 kips, was utilized for load testing. Afterward, the truck was allowed to run across the bridge at a crawling speed. The strains caused by the truck at the time it was driving across the bridge were then used to calculate the girder distribution factors (GDFs). By comparing the GDFs based on the load test to those using American Association of State Highway and Transportation Officials (AASHTO) Specification equations, it is found that the values calculated by AASHTO equations are conservative. Then, the Schmidt Hammer and the Ground Penetrating Radar (GPR) were used to estimate compressive strength of concrete and shear reinforcement spacing, respectively. The minimum requirement of prestressed tendons was determined by feasibility domain analysis with the original design load. The results showed that the number of tendons for all nine (9) bridges specified in the plans are fall in the range estimated by feasibility domain. With this proposed approach, lower bound and upper bound of the rating factors for each bridge can be estimated accurately when there are no plans. Also, this study suggests a guideline to evaluate the flexural and shear capacity when deterioration is identified. Based on the deterioration condition, the capacity of the structure can be recalculated conservatively by reducing the contribution of the materials.

ETD_8889

M.S.

Includes bibliographical references

by He Zhang

doi:10.7282/T3XK8K0D

ETD graduate

The author owns the copyright to this work.