Evaluation of a Highway Bridge Constructed Using High Strength Lightweight Concrete Bridge Girders

摘要

The use of high performance concretes to provide longer bridge spans has been limited due to the capacity of existing infrastructure to handle the load of the girders during transportation. The use of High Strength Lightweight Concrete (HSLW) can provide the same spans at a 20% reduction in weight. This paper presents the findings from an ongoing performance evaluation of HSLW concrete bridge girders used for the I-85 Ramp B Bridge crossing SR-34 in Coweta County, Georgia. The girders are AASHTO BT-54 cross-sections with a 107 feet 1112 inch (32.9 m) length cast with a 10,000 psi (68.9 MPa) design strength HSLW mix and an actual average unit weight of 120 lb/ft3 (1922 kg/m3). The prestressing losses measured experimentally by embedded vibrating wire strain gauges have been compared to the AASHTO LRFD loss equations, as well as the proposed methods by Tadros (2003) and Shams (2000). The investigation also included camber measurements and the effect of temperature changes. A load test was performed on the girders at 56-days of age and on the bridge after completion of construction to determine a stiffness estimator for use with the girders and to determine their performance as a completed system. The girders are the first use of HSLW girders in the state of Georgia, and they have proven to perform well for use in highway bridges.