UHPC Bridge Deck Composite with Galvanized Steel Press Brake Tub Girder Prefabricated Bridge Units

This new bridge construction project was a single-span, two-lane bridge, consisting of prefabricated bridge units utilizing a bridge deck of Ultra-High-Performance Concrete (UHPC) composite with a galvanized steel press brake tub girder (PBTG). The superstructure was 36 feet (11 m) wide and 35 feet (10.5 m) long. The prefabricated bridge units were placed at a center-to-center distance of 6 feet (2 m). The PBGT was formed by press brake into a trapezoidal box girder section. Angle braces were welded at 6 feet (2 m) increments along the girder and diaphragms were welded at each end. Shear studs were welded to the top flanges of the girder at 12-inch (30 cm) intervals.

The UHPC deck system was designed to act compositely with the galvanized steel PBTGs using the shear studs. The deck system consisted of a slab cast integrally on a stay-in-place galvanized steel form deck spanning in the transverse direction. The galvanized form deck consisted of 22 gauge formed sheet steel, conforming to ASTM A653 with a G235 hot dipped galvanized coating. The overall deck thickness of the deck was 6 inches (15 cm), of which the slab was 3 inches (7.5 cm) and the ribs were 3.0 inches (7.5 cm) deep ribs.

The units were connected across the width of the bridge using a field cast UHPC bridge deck joint connection.  In this connection, the transverse reinforcement bars from each unit were tied together with additional longitudinal reinforcement and the gaps between the panels were filled with UHPC. This connection provided continuity and load transfer between the units. UHPC for the units was mixed in a ready-mix concrete truck with no modifications as outlined in El-Tawil et al. (2023) and cast in a concrete plant. UHPC for the closure pours was delivered via truck and cast onsite.

This project demonstrated that new materials and new steel fabrication processes could be combined to produce a cost-effective, prefabricated, bridge with a 100-year maintenance-free service life. The project showed that a UHPC/ PBTG prefabricated bridge unit could be cost-effectively produced and installed at accelerated rate. The MDOT bridge worksheet indicated that the cost for a conventional bridge would be $788,000. The final cost to Clare County was $534,000, which included guardrail, paving, and epoxy overlay. The short-term savings were therefore $254,000 (32.2%). The slim and light weight system contributed much to the cost savings through lower transportation and handling costs and elimination for the need to camber the system. As a first-time endeavor, there was a steep learning curve associated with construction of this prototype and other opportunities for further cost reduction were identified for future efforts.

Figure 1: Construction of composite UHPC/ PBTG prefabricated bridge unit.

Figure 2: Construction process of the UHPC/PBTG bridge system.

Figure 3: Finished UHPC/PBTG bridge system: Mostetler Road over Mostetler Creek Bridge