Construction of Laboratory and Field Demonstration Modified Beam-in-Slab Bridges

Repairing/replacing deficient bridges is a major challenge for transportation system managers and is magnified for Low Volume Road (LVR) systems where inadequate structures need replacing due to structural and functional deficiencies. To maximize limited replacement funds, some local governments employ in-house forces to reduce construction costs, however most lack the resources to construct traditional bridge systems. The beam-in-slab bridge (BISB) system is a cost competitive alternative designed specifically for LVR systems. Consisting of W sections spaced 24 in. (640 mm) on centers and filled with concrete, the BISB system has been shown to be a sound replacement option, but however in some instances it is not structural efficient. To improve efficiency, composite action was obtained with an alternative shear connector (ASC); a transverse arch was utilized to distribute the wheel loads and reduce the self-weight. Both the section spacing and depth were increased resulting in the Modified Beam-in-Slab Bridge (MBISB) system. A full-scale laboratory test bridge (L = 31 ft. (9.45 m), W = 20 ft. (6.1 m)) was constructed to quantify the construction process, load distribution and failure modes of the MBISB. Unique to the construction was the transverse arch between the longitudinal girders formed with custom rolled re-useable formwork and minimal deck reinforcement. A MBISB demonstration bridge (L = 70 ft. (21.34 m), W = 32 ft. (9.75 m)) was designed and constructed without the use of specialized equipment in Tama County, Iowa. The bridge will be load tested in the summer of 2003 to compare its behavior with predicted values. Key words: beam-in-slab bridgecomposite actionlow volume road bridge replacement alternativ