May 12th, 2011
PRAISING INNOVATIONOptimize Mobility, by Catherine Higgins.
A federal innovation initiative is helping state departments of transportation employ proven technologies.
The FHWA Every Day Counts Innovation Initiative is aimed at encouraging state transportation agencies to be faster, greener and safer. According to the EDC website, “taking proven, and market ready technologies and getting them into widespread use” can help DOTs to be more efficient and effective when doing business.
UDOT uses and even leads the nation in many technologies promoted by EDC – for example, many Utahns are familiar with Accelerated Bridge Construction, which involves building a bridge off site, then moving it into place. ABC reduces project duration and saves money and time for road users. UDOT has moved more bridges than other state transportation agency.
Now through June, blog posts on four EDC areas of focus – prefabricated bridge elements, Adaptive Signal Control Technology, Warm Mix Asphalt and Geosynthetic Reinforced Soil – will show ways UDOT is making every construction day count and improving Utah’s transportation system for road users.
Prefabricated “LEGO” bridges
UDOT has constructed many bridges out of prefabricated elements. “Lego” type ABC construction is another way UDOT saves road users time and money, since very short road closures are necessary
The Tucker Bridge is located on U.S. – 6 at Mile Post 204 in Spanish Fork Canyon. With a 120 foot span and a 25 degree skew, the bridge is “a simple bridge” by design, says Ray Cook, Structural Designer for UDOT. Precast elements were designed to simplify the fabrication and construction as much as possible.
Though the bridge is on a curved alignment, the deck edges were designed to be straight and parallel to simplify the fabrication and construction of the precast deck and approach slab elements and to minimize the number of unique precast panels. The uniform pieces also saved the precast yard crew time and money during set-up.
The Tucker Bridge is UDOT’s second fully precast bridge supported on drilled shafts, required to support the wing walls as well as abutments. Each abutment consists of four precast segments, which were placed over the reinforcing steel cage extending from the drilled shafts. Each abutment was placed in less than a day, with the second abutment being placed in less than four hours.
Mile Post 200 Bridge
Mountainous geography and a geometrically complex Union Pacific Railroad crossing made the Mile Post 200 Bridge on U.S. – 6 a challenge to design. The old structure, a three span steel girder bridge, needed to be replaced on a new alignment. UDOT’s new bridge, which resembles a giant box culvert is “definitely different,” says Design Engineer Michael Romero. “There are not a lot of structures like this around.” Romero liked the complexity of the project which involved “doing things that haven’t been done before.”
U.S 6 and Union Pacific Railroad cross at a sharp angle with a skew of approximately 60 degrees. Additionally, the roadway superelevation is reversed in the middle of the bridge.
Taking all potentially conflicting conditions into account, Romero designed an extra wide, single span bridge with the U.S 6 traffic alignment running skewed across the deck. Granular borrow was placed on the structure to achieve the changes in superelevation. Asphalt is used as the pavement surface.
Because the structure is large, with a 107 foot long span and 303 foot width, over 480 total precast parts were required by the design.
Benefits of ABC
Through using ABC methods UDOT and road users have benefited from reduced project duration resulting in:
- Saved user costs – Reducing the duration of construction also reduces the duration of traffic delay, which has a real measurable cost to road users because of increased time spent in traffic.
- Improved safety – fewer accidents related to construction occur because project duration is reduced and construction is limited to off-peak travel times. Road users and construction crews have less exposure to risk.
- High quality – Construction of structures or superstructures in a controlled environment off-site gives workers “time to build these elements correctly,” says Doehring. Better workmanship can happen when construction takes place out of the pressure of working in live traffic.
Beaver Creek Bridge was built with prefabricated elements and also as a deck made out of Glass Fiber Reinforced Concrete. See HEAVY TRAFFIC CAUSING STRESS?
UDOT used oscillation-drilled shafts on the EXPRESSLink project on I-15.