Construction

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

Chapter 7

VDOT wanted all lanes open to traffic from 6 a.m. to 7 p.m. To achieve this, an additional disincentive was included for not having all lanes of the bridge open to traffic on time.

This additional disincentive accumulated up to $250,000 per day. Disincentives of this magnitude help ensure the contractor's buy-in to the owner's accelerated construction schedule and encourage the contractor to innovate.

The engineer's estimate for this project was $48.5M. The low bid by Archer-Western Contractors, Ltd., was $43.4M and 179 days calendar days with nighttime lane closures. The low bid was 11% or $5.1M less than the engineer's estimate. There were 5 bidders on this project, with the 2nd lowest bid about 3% or $1.5M more than the awarded low bid.

The contract specified that the contractor would receive $30,000 per day for early completion. The contractor replaced the 102 superstructure spans during only 137 night closures of half the roadway width. He received $30,000 for each of 42 nights, for a $1.3M incentive.

VDOT obtained a new superstructure ahead of schedule with less impact to the traveling public and with improved safety, and obtained it under budget.

The Lewis and Clark Bridge on State Route 433 over the Columbia River spans the state line between Longview, Washington and Rainier, Oregon and is jointly owned by the Washington State Department of Transportation and the Oregon Department of Transportation. The 1929 steel through-truss bridge was designed by the famed engineer Joseph B. Strauss and is listed in the National Register of Historic Places. It provides access across state lines for 18,000 vehicles each day.

In early 2000 its deck was severely deteriorated and required replacement. Accelerated onsite construction was needed to limit the impact to emergency services and to avoid extended use of a 40-mile detour west to the town of Cathlamet that included a ferry ride or an 80-mile detour south to Portland.

In 2004 WSDOT completed replacement of the bridge deck on this mile-long bridge with no impact to rush-hour traffic. Self-propelled modular transporters (SPMTs) were used to replace 3,900 ft of deck during 124 night closures plus 3 weekend closures. A helicopter with landing pad was provided on the south side of the river for emergency crossings during the closures. Construction using conventional castin- place methods would have required 4 years.

The deck replacement extended the life of the bridge another 25 years.

In the contract plans, the Washington State DOT had designed prefabricated fullwidth full-depth deck panels and a placement procedure to accommodate the required rapid construction schedule. One contractor, Max J. Kuney Company of Spokane, partnered with an SPMT supplier in the development of his bid, assuming a revised placement procedure that used SPMTs in combination with a speciallydesigned steel truss frame for lifting and transporting. Their bid was considerably lower than the other bidders. Kuney was awarded the contract, and WSDOT accepted their proposed system.

The 5,478-ft long bridge included 3 deck-truss spans at 168 ft, 337 ft, and 337 ft; 3 through-truss spans at 760 ft, 1200 ft, and 760 ft; plus approach spans. Of this total length, 3900 ft of the deck was replaced with 103 prefabricated deck panels that were 36 ft wide and 20 ft to 45 ft long (20 at 45 ft, 45 at 40 ft, 20 at 35 ft, 14 at 30 ft, and 4 at 20 ft). The lightweight concrete panels were 6-in. thick plus 1-in. thick overlay. Each panel was supported on two longitudinal steel support beams and had a maximum panel weight of 96 tons. The new deck eliminated the existing 3-ftwide raised sidewalks, providing 5-ft shoulders at road level for bicyclists and pedestrians as well as additional room for traffic to maneuver around disabled vehicles.

The bridge was closed on Sunday through Thursday nights from 9:30 p.m. to 5:30 a.m. The SPMTs with truss frame moved a new panel to the top of the bridge, lifted the old panel out, and then lowered the new panel into place before taking the old panel off the bridge. Each panel movement took an average 6.5 hours. Use of this prefabricated deck system in combination with the innovative SPMT equipment reduced construction workers' exposure to traffic during construction, improved the constructability of the bridge, and allowed the bridge to remain open for normal weekday operations.

WSDOT utilized an "A" + "B" + "C" bidding method to determine the lowest responsible bidder, where "A" equals the bid items, "B" equals the total number of bridge closures established by the bidder to complete the work times the Total Bridge Rental Closure Cost of $8,000, and "C" equals the total number of single lane closures established by the bidder to complete the work times the Bridge Single Lane Rental Cost of $2,000. The "B" and "C" parts of the bid were only used to determine the lowest responsible bidder, not to determine final payment to the contractor.