Olson, Steven A.

Prestressed concrete has been used as a bridge construction method in the United States since 1949. Presently, there are thousands of pretensioned prestressed concrete bridges in service in North America. Each year, approximately 200 girders are damaged as a result of impact damage (primarily overheight vehicles striking a bridge from below). This report describes the results of a four girder test series used to evaluate impact damage and effectiveness of repairs. The girders used for the study were fabricated in 1967 and placed into service. The girders were removed from service in 1984 as a result of a road realignment project. The objectives of the research project were to: 1) determine the effective prestress in the strands after 20 years; 2) determine the influence of impact damage on girder performance; 3) evaluate the performance of two impact damage repair schemes under static, fatigue and ultimate loadings; and 4) develop a model to estimate the strand stress ranges in damaged girders.

In the interest of providing tools for the cost-effective maintenance of an aging inventory of bridges, a method for comparing feasible repair/replacement sequences for low-slump concrete overlays for bridge decks is developed. The method relies on a technique for computing deterioration curves using inspection data from the National Bridge Inventory. Over twenty years of inspection data for bridge decks in Minnesota, which were overlaid with low-slump concrete overlays placed between 1974 and 1981, was used. The deterioration curves were assumed dependent on several material and geometric variables identified by means of a literature review, and the statistical significance of these parameters on deterioration rates was examined. These variables include span length, average daily traffic, and superstructure material type, and piecewise linear deterioration curves were constructed for various subgroups with similar deterioration characteristics. Present value cost analysis was used to price the available options by identifying the sequence of repairs that has the least cost while maintaining a specified performance measure. The present value analysis considers the costs and timing of repair/replacement sequences, inflation, and the discount rate.