Design of I-40 Bridges in Guadalupe County, New Mexico

Abstract

The I-40 in Guadalupe County, New Mexico, contains a set of three bridges. They are medium-span overpasses accommodating two lanes of traffic each. The design team used this routine forum to address several design problems with innovative solutions. In addition, aesthetics were considered from the early stages of design. These two-span bridges are designed continuous for live load by using high-strength prestressed concrete U-beams and cast-in-place deck construction. Three-point bearing provides uniform support of the girders. To alleviate problems with harping and end debonding, strands were added in the top flange, debonded in the center of the beam, and then cut after release. Spread footings on top of backfill of mechanically stabilized earth support the abutments to reduce differential settlement between the approach and the abutment. Differential settlement between pier and abutments was included in the design to account for differences in footing support. The semi-integral abutment stubwall was shortened on each end to allow the integral wingwalls to slide freely; this solved a common movement restraint problem. Aesthetics were considered from the beginning of the project. Three-dimensional modeling was used to visualize the completed form. Artwork was created to form uniform recessions in the concrete. Average bridge costs for these structures, including aesthetics, were below state average. This economy can be attributed to several factors, including simplicity and construction considerations in design, consultation during design with suppliers and contractors, use of repetitive parts and materials, and a creative bid process.