FIELD PERFORMANCE OF PRESTRESSED HIGH PERFORMANCE CONCRETE HIGHWAY BRIDGES IN TEXAS

Abstract

Two prestressed high performance concrete (HPC) highway bridges were constructed in Texas utilizing concrete with 56 day design strengths of up to 97 MPa (14,000 psi). The utilization of HPC allowed for longer spans and larger girder spacing than typically used in conventional prestressed concrete bridges. An extensive research program was conducted to monitor the short- and long-term structural behavior of these unique highway bridge structures. The Louetta Road Overpass near Houston, Texas, consists of two adjacent three-span simply supported HPC highway bridges. The Louetta bridges utilize the Texas U-beam in conjunction with high performance concrete and 15 mm (0.6 in.) diameter prestressing strands, resulting in an efficient structural design. The North Concho River/US 87/S. O. R. R. Overpass in San Angelo, Texas, consists of a 290 m (951 ft) long eight-span HPC Eastbound bridge and an adjacent 292 m (958 ft) long nine-span conventional concrete Westbound bridge. Both bridges utilize the AASHTO Type IV beam cross-section in the main spans. HPC was used in conjunction with 15 mm (0.6 in.) diameter strands to increase span lengths and girder spacing in the Eastbound HPC bridge relative to the conventional concrete Westbound bridge. As part of the research program, instrumentation gauges were placed in selected structural components of the bridges. These gauges were monitored through the construction process and into the service lives of the completed bridges. Data were collected on prestress losses, beam deflection (camber), concrete strains, and concrete temperatures. These data were analyzed to examine the applicability of current standard design procedures and assumptions for highway bridges using HPC, and to compare the structural behavior of the two bridges, which represent similar yet different implementations of HPC in highway bridge structures.