Bridge Description

41st Street over the Big Sioux River in the City of Sioux Falls in Minnehaha County

Tier 6 (longer but reduced by months/years)

ABC: 113 days with two-stage construction ; Conventional: one year with two-stage construction

reduced traffic impacts – critical arterial; improved site constructability – no deck forming required

305-ft-long and 112.33-ft wide three-span bridge (90 ft - 125 ft - 87 ft)

47000

Traffic management alternative, if constructed conventionally: extended use of detours onto city streets

The existing six-lane, three-span bridge was 282-ft-long and 106.83-ft-wide with 15 steel I-beams at 6.5 ft and 7.0 ft spacing per span. Built in 1965, and widened at a later date, the bridge is located in the city’s business district on the busiest street in the state of South Dakota, the bridge was initially to be replaced by the US Army Corps of Engineers as part of a flood control project to improve the safety of the levee along the Big Sioux River. Because of its deteriorated condition and potential impact on traffic, the City of Sioux Falls decided to replace it with accelerated methods, ahead of the levee project.

The seven-lane replacement bridge has 19 adjacent precast pretensioned concrete box beams per span, with a composite 5.5-inch-thick cast-in-place concrete deck. The Colorado DOT standard box beams were 4.5 ft deep and 5 ft and 6 ft wide. The cross-section also included 4-ft outside shoulders as well as sidewalks separated from traffic lanes by concrete barriers.

The bridge was constructed in two stages with two 11-ft-wide lanes of traffic in each direction maintained during each stage. The steel H-pile concrete-encased wall piers were constructed prior to removal of the existing piers to speed construction. The integral abutment was founded on a single row of H-piles. The adjacent beams were erected and transversely post-tensioned with tie-rods. The deck was cast end-to-end with no transverse joints; the deck was cast at the minimum rate of 40 cu yds per hr using a set retarder. A full-depth concrete closure joint was cast between the stages of construction.The contract required completion of the bridge within 160 days for the bid to be responsive. The incentive was set at five to six percent of the estimated cost, for a maximum incentive of $500,000. The contract included a $250,000 lump-sum incentive payment if the project was completed within the number of days bid in the awarded contract. An additional $10,000 incentive was included for each day the project was completed earlier than the number of days bid.The awarded contractor bid 140 days. The actual construction duration of 113 days resulted in a 70% time savings compared to conventional construction. The contractor received the maximum incentive of $500,000.

The adjacent box beams were a new beam for the state of South Dakota. The local fabricator commented that since they constructed the precast box girder for this project, the learning curve for these types of precast members is reduced and would they would readily bid these types of structures on future projects. Also, the contractor stated that adding a precast overhang would have accelerated construction, although costs would not likely have been reduced.