Innovate 80

12 major bridge structures replaced on ambitious highway project

UDOT’s aggressive approach in using accelerated bridge construction techniques especially the utilization of SPMTs has earned the department national acclaim. The main factor in using the ABC process is to significantly reduce road closures and minimize traffic delays.

“With SPMT technology, if it makes sense to do it this way, we’ll do it. It’s the wave of the future for UDOT.” Deryl Mayhew, UDOT Region 2 resident engineer.

“It’s amazing how Utah has been courageous, in a sense, to capitalize on the latest in technology with SPMTs. I think their goal is very ambitious and doable.” Benjamin Tang, Oregon DOT bridge preservation engineering manager.

By Brad Fullmer

The last of 12 bridge structures utilizing self-propelled modular transporters was moved into place Aug. 23 in Salt Lake City, capping a whirlwind of accelerated bridge construction activity this summer for the Utah Department of Transportation, a project cleverly titled Innovate 80.

The 33rd South bridge at Interstate 215 was the final of eight bridges constructed this year by Draper, Utah-based Ralph L. Wadsworth Construction Co. and moved into place via SPMTs operated by Mammoet, USA, of Rosharon, Texas. Seven other RLWCC bridge structures were moved during a six-week period along the Interstate 80 reconstruction project corridor from late June to early August.

advertisement

Additionally, four bridge structures built by Wadsworth Bros. Construction of Draper, Utah, were moved into place on I-80 up Parley’s Canyon between the Mountain Dell and Lambs Canyon exits, east of Salt Lake City, over two consecutive weekends in mid-August. The four bridges were demolished and replaced in an unheard-of 37 hours over the two weekends.

“It’s the fastest bridge replacement I’ve ever heard of it went much better than expected,” says Deryl Mayhew, resident engineer on the $11 million bridge replacement project for UDOT’s Region 2. “(WBC) finished the first weekend moves two hours early, and the second weekend was completed eight hours early. We attribute that success to the contractor learning what to do differently.”

Mayhew says the approach slabs were the tricky part of the entire move. “They did a fantastic job of figuring out a better way to do it that second weekend, which saved a ton of time,” he adds.

One unique aspect of the I-80 Parley’s Canyon bridge replacements, compared to the other I-80 bridge moves and 33rd South, was that WBC proposed utilizing the SPMTs. The project was initially bid to be built via more traditional construction methods.

“The project was design-build and we were given the choice to do it by having bypass roads and diverting traffic on I-80 around the bridges and doing it at our own pace,” says Guy Wadsworth, WBC president. “We figured that the geometry wouldn’t work, so at the last minute we decided to use SPMTs. We had to put together (another) bid in five days. Our (project) is the first where (the contractor) elected to use SPMTs.”

Design engineer Paul Blackham of Stanley Consultants of Salt Lake City, says the superstructure replacements were staged on temporary abutments, which were designed and constructed on haul roads to match the grades required to drive the SPMT trailers underneath the temporary abutments, then lift them and transport them to rest on the existing abutments.

The removal of the existing structures at Lambs Canyon was done by conventional demolition methods, while at Mountain Dell, a demolition abutment was designed, as well as a temporary abutment that doubles as both a staging area for new construction and a demolition staging area.

The approach slab replacement required staging the construction of the approach slabs adjacent to the bridges. The casting of the approach slabs included post-tensioning ducts that were embedded in the monolithic slabs with reinforcing steel. After the slabs cured, they were cut into segments, lifted into their final positions and post-tensioned together.

“Originally, it was just going to be a deck replacement,” Blackham says. “As we looked at different possibilities, the contractor found it was cheaper to replace the entire superstructure. That was pretty unique in itself.”

Wadsworth adds: “We did the four bridge structures in 37 hours total that comes out to nine hours each. That’s a record, anywhere. All my guys were pretty proud of what we were able to accomplish.”

Wadsworth says the four approach slabs weighed approximately 54,000 lbs each. “It’s difficult to replace approach slabs,” he adds. “We site-cast the approach slabs and the grade had to be nearly perfect to set them.”

Mayhew says that using SPMTs was by far the best way to do bridge moves such as these. “On Mountain Dell and Lambs (bridges), it was the only way to do it, considering traffic impacts” he adds.

Minimizing Road Closures, Impact to Traveling Public

The entire reason to use accelerated bridge construction, or ABC, techniques particularly SPMTs is to minimize the length of road closures and the impact they have on the traveling public, says Mayhew. He estimates that on the I-80 Parley’s Canyon bridge replacements, typical construction methods would have backed up traffic up to an hour in each direction over a six-month construction schedule. That works out to about 190,000 hours of delays saved based on current traffic volumes, which Mayhew says equates to over $2.5 million in delay costs. In addition, Mayhew says WBC’s bid of $11 million was already $2 million less than the next closest bid.

“With SPMT technology, if it makes sense to do it this way, we’ll do it,” he adds. “It’s the wave of the future for UDOT.”

The $4.5 million 33rd South bridge was also replaced in lightning-fast time a mere 19 hours 36 hours less than the 55-hour window allotted to Ralph L. Wadsworth Construction Co. crews, according to the firm’s Tod Wadsworth. Even though RLWCC has the most experience to date of any Utah contractor with ABC techniques, dating back to its first SPMT move last October (45th South I-215 East bridge), this project required careful analysis and coordination to be completed in less than 24 hours.

RLWCC supervisor Doug Clements says moving the 33rd South bridge from its staging area about 1.5 mi south of the project site was difficult because of utilities in the area. Steel plates were bridged over a high-pressure gas line along Wasatch Blvd. as a cautionary measure, even though the 1.6-million-lb bridge weighs nearly half of what the 45th South bridge weighed (3 million lbs.).

A crossover had to be constructed to move the bridge from Wasatch onto I-215, and traffic signals, power lines and other utilities were removed and replaced to allow for the move.

Clements says the ABC process with SPMTs has gotten smoother with repetition, although nothing is ever taken for granted when dealing with mammoth bridge structures.

“Everybody on our team knows what to do, and what to expect,” he says.

The 33rd South bridge, which at 80 ft wide and 130 ft long is the third-largest bridge of the 12 moved by RLWCC, utilized a manufactured lightweight aggregate made by Utelite of Coalville, Utah. The manufactured aggregate weighs about 115 lbs per sq ft, compared to 150 lbs per sq ft for regular stone, according to Jim Deschenes of Michael Baker Corp. of Midvale, Utah, design engineer for both the 33rd South and 45th South bridges.

“Most of the weight savings was in the lightweight concrete, along with optimized steel girders,” says Deschenes.

Other construction aspects of the 33rd South bridge replacement performed by RLWCC included incorporating a permanent, self-performed shoring system on the west abutment that required the use of a one-sided forming system and wing-wall pours.

Abutments incorporated the use ofa post-tensioning system to reduce rebar, increase strength and reduce shrinkage,an innovative idea that helped reduce the overall weight applied to the ground.

Piles were also placed outside of the existing 33rd South bridge footprint for the new abutment foundations. The post-tensioning system allowed for abutments to span from one pile foundation to the other. This made it possible to construct the new abutments under the existing bridge in an efficient manner, as well as keeping traffic flowing on 33rd South for the construction duration.

Overall, the entire Innovate 80 bridge replacement schedule has garnered UDOT national acclaim.

“Utah is really doing a great job in leading the nation in using accelerated bridge construction and bridge movement technology,” says Benjamin Tang, bridge preservation engineering manager for Oregon DOT, and a former principal engineer for the Federal Highway Administration’s office of bridge technology department. “It’s amazing how Utah has been courageous, in a sense, to capitalize on the latest in technology with SPMTs. They are at the forefront because they are going at it whole hog. I think their goal is very ambitious and doable. Doing bridge (replacements) overnight and on weekends has not been done elsewhere, in terms of the number of repetitions.”

“SPMTs def have a place,” says Kevin Thompson, state bridge engineer for CalTrans in Sacramento. “They may not be the preferred choice in every case where you want to accelerate bridge construction, but they are a definite tool. If the shoe fits, it’s really a good alternative.”

“I think it’s very innovative and it makes some sense for some structures,” says Jimmy Camp, engineering support division director for New Mexico DOT. “We don’t see an application presently, but we believe we’ll have an application for it in the future.”

“We’ve done a lot of bridges in the U.S.,” says Bill Halsband, vice president of business development for Mammoet. “But UDOT is definitely leading the way (with ABC techniques). They’re the most aggressive at it, so far.”

Halsband says in addition to Utah, Mammoet has provided SPMTs for state DOT projects in Oregon, Florida, Washington, Louisiana and New York, which have all done at least one ABC project to date. He adds that several other states becoming more interested in the process.

What is an SPMT? By Brad Fullmer Mammoet’s self-propelled modular transporters that were utilized on the Innovate 80 bridge replacement project along Interstate 80 in Salt Lake City are truly state-of-the-art, highly technical pieces of equipment. Each SPMT can be assembled in units of 4 or 6 axle lines to form trailers for the required carrying capacity. Each axle line consists of four wheels arranged in pairs and can support a maximum load of 33 tons, in addition to its own weight, ground conditions permitting. Each pair of wheels can pivot 360 degrees around their support point; as a result, an SPMT has complete freedom of movement in all horizontal directions. Through its complex hydraulic suspension system, equal loads are maintained independently on each axle, even on irregular surfaces. The bed of the SPMT can be raised up to 24 in and tilted in either direction to maintain a horizontal bed on an inclined surface. Grades as steep as 8 percent have been done, but the maximum grade depends on site-specific conditions. Vertical lifting equipment can be mounted on the SPMT platform if required. The SPMT is self-propelled and can be coupled longitudinally and laterally to form multiple units; it has a maximum speed of 3.75 mph. A single operator controls commands via a portable control panel (called a ‘joy pack’) that is wired to a power pack, which controls the main computer, hydraulic pump, generators, etc. The controller has four basic commands: steering, lifting, driving, and braking. A series of interconnecting cables link all trailer computers together, which allows for greater flexibility and control. Stability is a major factor to consider when moving multi-million lb structures. Three-point support is optimum, and can be realized by dividing all wheel bogies into three groups, which are connected hydraulically. Wind speed and slope must be factored into the equation to ensure stability is maintained. Bill Halsband, vice president of business development for Mammoet USA, says on the Innovate 80 project, 68 lines were used on the seven northbound I-80 bridge replacements from 1300 East to State Street, while 48 lines were used on the four I-80 Parley’s Canyons bridges, along with the 33rd South I-215 bridge. “The SPMTs can be bolted in any configuration to match the weight that is needed to be transported,” says Halsband. The operators of the SPMTs are highly-skilled technicians who are put through rigorous training in order to keep up with the latest technological advances. Two operators were used on the 12 bridge replacements on Innovate 80. “You can’t just put anyone on this,” says Halsband. “It’s very sophisticated technology. The SPMTs are constantly upgraded. Our guys go to school regularly and we work constantly with the manufacturer to develop better systems and get better functionality.” Halsband says the heaviest bridge structure on Innovate 80 was 2.6 million lbs. Mammoet holds the world record for the heaviest object moved on rubber tires a massive offshore oil platform in England in 2005 that weighed a staggering 12,800 metric tons or 28.16 million lbs.

Click here for next Feature Story >>