Construction

Prefabricated Bridge Elements and Systems Cost Study: Accelerated Bridge Construction Success Stories

Chapter 5

The State of Ohio has the second largest number of bridges in the United States and the seventh largest highway system. Like many states, portions of the system are outdated, overburdened and in need of repair. Many areas of the Buckeye State are becoming highly populated and developed, resulting in increased traffic volumes. The additional motorists on the roadways necessitate adding lanes on many of the routes. To accomplish this task, road crews have to close or restrict lanes during the construction process. Such closures and restrictions negatively impact motorists in terms of lost time, higher fuel costs, and lost revenues. The Ohio Department of Transportation (ODOT) is committed to the continuous movement of traffic through all work zones by the elimination or reduction of delays.

ODOT's U.S. Route 22 Bridge over the Scioto River, in Pickaway County 30 miles south of Columbus, provides access for the 12,900 vehicles that cross it each day. It is a vital link for the local school district, the local trucking industry transporting harvest crops to mills, and emergency response services. The existing 45-year old concrete slab and steel girder bridge, built in 1957, had deteriorated girders and a roadway width that was too narrow for the local farm equipment. A 2003 design-build project replaced the deteriorated superstructure with a wider bridge, in one of ODOT's first accelerated construction projects under its Fast Track Bridge Program strategic initiative to build bridges faster, smarter, and better.

Adjacent site constraints required that the new superstructure be constructed in the same location as the existing bridge. The design-build team of Ruhlin Construction Company and E.L. Robinson Engineering Company developed a new superstructure consisting of high performance steel girders and high performance concrete deck, and a galvanized steel pier cap replacement for the rehabilitated and widened substructure, in combination with other innovations to achieve the required accelerated onsite construction timeline. The bridge was completely closed during construction, which began when school closed in mid-June 2003, and it was required to be back in service in 60 days, by the beginning of the fall harvest in August. Traffic was maintained on a 20-mile detour during the closure.

The U.S. Route 22 Bridge was completed in just 48 days, despite heavy rain and flooding. Construction would have taken 18 months using conventional methods.

The existing 6-span 634-ft long, 35.4-ft wide U.S. Route 22 Bridge superstructure was replaced and widened to 44.2 feet to upgrade the 2-lane bridge by increasing the two shoulders from 3 ft to 4 ft, and by adding an 8-ft sidewalk.

While much of this bridge replacement project used conventional design and construction methods, adjustments were made to maximize onsite construction speed. The five new girders per span were made of high performance steel and fabricated by Stupp Bridge Company in Kentucky. They were designed to be simply supported to streamline erection, and made continuous with integral concrete diaphragms over the piers. The integral abutments on this bridge make it ODOT's longest bridge without expansion joints. Galvanized permanent metal deck forms provided a stay-in-place deck forming system instead of the traditional wooden deck forms that would have to be removed.

The widening of the substructure was also designed and constructed to shorten the onsite construction time. The existing piers were saw-cut below the pier-stem construction joint and replaced with galvanized steel plate girder bent caps that extended to groups of four concrete-capped galvanized steel 18-inch diameter pipe piles under the widened portion of the bridge. Pipe piles for several of the piers under the widening were driven before the bridge was closed to further shorten the bridge closure time.

Other details to speed onsite construction included demolition of the existing deck beginning at the middle of the bridge and simultaneously working toward the abutments because environmental restrictions prevented river access. Other details included beginning the retrofit work on each pier as soon as the existing girders were removed, shipping and erecting the new girders as soon as the pier retrofits were completed, and using two concrete pumps to avoid delays during the deck pour.

The bridge is expected to see a 75-year service life due to the use of high performance concrete in the deck, high performance steel girders, galvanized steel plate girder bent caps, galvanized steel pipe piles, and good construction practices. ODOT has partnered with the University of Cincinnati to evaluate the piloted features of the contract.

The Ohio DOT awarded this design-build project based on responses to a bid package that included a Scope of Services and a set of the existing bridge plans from 45 year ago. The Scope of Services required that the bridge be closed a maximum of 60 days.

In addition, incentive/disincentive clauses were included in the contract to help ensure completion of critical activities to open the bridge on the accelerated schedule.

The contract specified Liquidated Savings of $50,000 for each day that all necessary work was completed prior to the maximum 60-day closure requirement, with maximum Liquidated Savings of $500,000.

The contract also specified Liquidated Damages for completion after the specified maximum 60-day closure. The Liquidated Damages were assessed at $20,000 per day for opening the bridge in 61-65 days, $30,000 per day for 66-70 days, $40,000 per day for 71-75 days, and $50,000 per day if the bridge remained closed for 76 or more days.

The engineer's estimate for this project was $5.0M. The low bid of $2.7M from Ruhlin Construction Company was 46% or $2.3M less than the engineer's estimate. There were 4 bidders on this project, with the 2nd lowest bidder 19% or $500,000 higher than the low bid.

The bridge was completed in 48 days, 12 days ahead of schedule and without a single lost-time injury. The contractor received the maximum $500,000 incentive.

This Ohio DOT Fast Track design-build project replaced the existing deteriorated bridge with a wider superstructure in significantly less time than conventional construction, and it was completed significantly under budget. It demonstrates quite effectively that cost-effective, long-lasting accelerated bridge construction projects can be built through the innovative use of conventional construction in combination with high performance materials and good contracting strategies. ODOT has continued their Fast Track Bridge Program with subsequent accelerated bridge construction projects.

In 2000 the Texas Department of Transportation's State Highway 66 over Lake Ray Hubbard in Rockwall County northeast of Dallas was a narrow, congested, 40-year old 2-lane bridge. It was replaced with a pair of bridges, completed in early 2003. The new 4,360-ft long, 40-ft wide eastbound bridge has two traffic lanes and shoulders, and precast bent caps as part of its substructure due to a contractorinitiated field change.

Precasting 43 identical caps resulted in a time savings of 5 to 7 days per cap, at least 215 days of effort. Forming, concrete placement, and curing for conventional bent caps would have required 7 days of critical path activity per cap. This represented a total potential delay of 9 months for the 43 bent caps, a delay that would have required additional overhead costs and slower project delivery.

First the new westbound bridge was built adjacent to the existing bridge using conventional construction. Traffic was then moved to the new bridge, the old bridge was demolished, and the eastbound bridge was built approximately on the bridge's original alignment.

The contractor fabricated the 43 identical caps adjacent to one end of the bridge. The precast reinforced concrete caps are 37.5-ft long with beveled ends and a 3.25- ft square cross section. Each cap is supported by three 3-ft diameter cast-in-place columns, and provides the bearing for five AASHTO Type IV beams per typical 100- ft span. TxDOT designed grouted-duct connections between the precast caps and the cast-in-place columns based on previous research at the University of Texas at Austin. Seismic design was not required.

In addition to speeding onsite construction, fabricating the bent caps off the critical path allowed the use of a normal-strength high performance concrete mix design that results in greater durability but with a slower strength gain due to the 35 percent replacement of cement with ground-granulated blast-furnace slag.