Development of a High Performance Substructure System for Prestressed Concrete Girder Highway Bridges

The precast, pretensioned concrete I-beam and cast-in-place concrete slab superstructure using stay-in-place pretensioned deck panels is the prevailing system for short- and medium-span highway bridge construction in much of the United States today. High strength materials, plant production methods, repetitive elements and standardized details all contribute to the efficiency of this system. Although this technology has been dominant for several decades, the overwhelming preponderance of substructures for these same bridges consists of cast-in-place reinforced concrete. A predominantly precast, post-tensioned substructure system for such bridges has been developed in this thesis. While cast-in-place construction techniques are utilized to a limited extent, the system was developed to benefit from the advantages inherent in precast production including: high strength and high performance materials, economies of scale, efficient standardized production and faster on-site erection times. Precast techniques also provide much needed aesthetic improvements through flexibility in utilization of attractive forms and surface textures. Environmentally sensitive sites are spared many of the disturbances that accompany cast-in-place operations. Application of the system to single and multi-column bent shapes is considered based on the general range of applications for precast, pretensioned I-beam bridges. Current Texas bridge design practice and previous uses of industrialized processes in concrete substructure production worldwide are reviewed. Aesthetic substructure design for moderate-span highway bridges is addressed. Potential element fabrication and erection techniques are discussed, and examples of standard system element designs are presented. The aesthetic and economic impact of the proposed substructure system is considered.