This article provides details of the design and construction of the Twisp River Bridge, a 60.0 m (197 ft) long single-span bridge in the North Cascade Mountains in Washington State. New 2.4 m (7.87 ft) deep WSDOT W95PTMC girder sections were used in the construction. The girders were delivered to the site in three precast, pretensioned segments, erected on falsework bents, and post-tensioned together after the roadway deck was placed. High performance concrete (HPC) with a 28-day strength of 55 MPa (8.0 ksi) was used for the girders. The girder closure pours required a strength of 35 MPa (5.0 ksi), while all other cast-in-place concrete had a specified strength of 28 MPa (4.0 ksi). High-load reinforced elastomeric bearings, designed by AASHTO Method B, were used at the ends of the girders. This was the first use of elastomeric bearings by WSDOT in a posttensioned bridge. All post-tensioning anchorages were placed in a cast-in-place concrete end diaphragm. The authors provide a summary of the design features of this project, the challenges involved, and the lessons learned from it.
