ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306900
36 | ASPIRE , Summer 2007 Intricate and creative designs for once- in-a-lifetime bridges garner awards and acclaim, but designers are most in need of ideas for the typical bridges they design and build every day. The Guadalupe County I-40 Overpass bridges, a set of three structures, gave designers with the New Mexico Department of Transportation an opportunity to solve recurring problems, create strong aesthetic appeal, improve durability, and stay under budget. The design, featuring precast concrete U-beams and cast-in- place concrete decks, provides a strong option for many future bridges. The new structures, which cross I-40, replaced bridges that were functionally obsolete and structurally deficient. Two of the bridges carry local traffic on minor arterial roads, while the third carries U.S. Route 84. The new structures were offset from the original bridges allowing free design within standard roadway parameters. A cross section consisting of two 12-ft-wide lanes with 6-ft-wide shoulders, for a total roadway width of 36 ft and a bridge width of 39 ft, met the standards for the arterial roads. Eight- ft-wide shoulders were required on the U.S. Route 84 bridge, creating a total roadway width of 40 ft and bridge width of 43 ft. Interstate 40 carries many travelers and tourists, and the bridges welcome people to the state and to Guadalupe County. To enhance that welcome, strong aesthetics were desired for these bridges. The design also had to reflect the local color of the area and be tied together to establish continuity. Identical Structures Created Efficiency The designers decided that the easiest way to approach this challenge was to create identical structures for all three bridges, so artwork could then reflect each locality, while the bridges provided continuity. As a result, the design had to fulfill the requirements for all three bridges. This task was simplified because the interstate highway maintained a consistent width throughout the project length. After considering a variety of options, the designers decided to create two-span bridges with a pier in the center of the median. Large, unconstrained areas of slope paving on steep slopes have created problems in the past, so the team was asked to avoid using steep slopes constrained by slope paving as the support at abutments. Using self-stable slopes would have added 50 to 60 ft to each roadway side, creating spans of about 150 ft, which would have required an increase in road height of 9 in. or more. Mechanically-stabilized earth (MSE) walls proved to be a better value economically and were thought to have better aesthetic potential for the given profile Guadalupe County I-40 overpass brIdGes / GuAdAluPE County, nEw MExICo EngInEEr: new Mexico department of transportation, Santa Fe, n.M. PrImE ContraCtor: Reiman Corp. subcontracted to James Hamilton Construction Co., Silver City, n.M. mSE Wall SuPPlIEr: Costillo Ready Mix Concrete, Inc., Belen, n.M. Pr ECaStEr: Coreslab Structures Inc. (formerly Rinker Materials), Albuquerque, n.M., a PCI-Certified Producer Enhancing the 'Bread and Butter' by Joan D. Bowser, Zann Jones, Jimmy D. Camp, and Robert Meyers, New Mexico Department of Transportation typical new mexico bridges use innovative designs featuring precast concrete u-beams and cast-in-place concrete decks ASPIRE_Summer_2007.indb 36 5/15/07 11:43:36 AM