Figure 11: Artist's Rendering of "Big I" Interchange Figure 12: An Early "Big I" Segment

by: Jimmy D. Camp, State Bridge Engineer, New Mexico State Highway and Transportation Department The "Big I" interstate-to-interstate interchange in Albuquerque (Fig. 11) is located at the junction of I-40 and I-25. It is the busiest interchange in New Mexico with an ADT of approximately 300,000 vehicles per day. The "Big I" project scope calls to upgrade the "Big I" interchange to 5 levels, add frontage roads parallel to the main lines and upgrade the four mainline legs for some distance each side of the interchange. This is the largest transportation project ever constructed in New Mexico. The design was completed in about 18 months, and the construction is to be completed with no more than 24 months of interstate traffic disruption. Traffic disruptions will begin in the latter part of June 2000. There are a total of fifty-five bridges in this project, of which 8 are "fly-over" bridges. The eight "fly-over" bridges range in overall length from 600 feet to 2500 feet with a maximum span of roughly 200 feet. These "fly-over" bridges will support both one or two-lane curved elevated ramps. Approximately 320,000 square feet, or 7.4 acres of bridge deck is required for these segmental "fly-over" ramp bridges. The "Big I" project bids were due on January 27, 2000. Five bids were received with the low bid of $221,847,235 from Twin Mountain Construction Co., a Kiewit Construction affiliate. The segmental bridges bid near $83 per square foot. The contractor was told to begin work in mid-February 2000. The project has and is continuing to progress at a record pace. The segments are all single-cell constant depth segments. The balanced cantilever method of segmental bridge construction will be used to erect these bridges. Two standard segment shapes are being used; one for the single-lane bridges and one for the double-lane bridges. The segments were designed to have a maximum weight of 60 tons, but were changed to 85 tons upon request from the contractor. Six hundred sixty-three concrete segments will be cast from June 2000 through July 2001. The segments are scheduled for erection from August 2000 through December 2001.

The segmental casting yard has 5 casting beds ã 3 double-lane casting beds (2 for the regular segments, and 1 for the pier segments) and 2 single-lane casting beds (1 for the regular segments, and 1 for the pier segments). The casting yard is located adjacent to the "Big I" project site. The segmental casting yard has been assembled and is now casting segments. One of the first segments produced is shown in Fig. 12. The "Big I" project is progressing very quickly. The segmental bridge work has been on an extremely rapid schedule. The segmental bridge design kept the segments very uniform. Uniformity and straightforward design details have allowed the contractor to move the segmental portion of the project work along very quickly. A site was provided by the owner, which allowed the casting yard to be set up immediately. Some of the various permitting work was done in the design phase of the project, which allowed the contractor to get to work without delays. The designer, owner, and contractor have worked very closely together. Numerous detail and design changes on the segmental bridges were requested by the contractor. A good working relationship of all parties has allowed many of these requests to be incorporated into the project. The main players that have allowed changes to be incorporated into the project are URS Corporation, Twin Mountain Construction Company, Finley McNary Engineers, Inc., the Federal Highway Administration and the New Mexico State Highway and Transportation Department. Schwager Davis, Inc., is supplying post-Tensioning materials, and The D. S. Brown Company is supplying bearing assemblies and modular expansion joint assemblies. Working together, with the goal to get these segmental bridges built in a short time frame has worked well as all involved parties have remained focused yet flexible. We feel the precast concrete segmental "fly-over" ramp bridges will serve New Mexico well for many years to come. We are quite excited to introduce segmental bridge construction to New Mexico. We feel confident that we have made the right choice of segmental bridges for the "fly-over" ramps on the "Big I" project.