ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/575053
PROJECT US 17-92 INTERCHANCE AT SR 436 From congestion to concrete innovation by T. J. Lallathin Jr., DRMP Inc.ation Revamping one of the most congested intersections in the state of Florida was no small feat. With over 100,000 motorists traveling daily through the US 17-92/SR 436 intersection, located in Casselberry, Fla., designing and constructing a grade-crossing structure to alleviate traffic presented multiple challenges. These challenges included accommodating the Florida Department of Transportation (FDOT) District Five's budget, an accelerated schedule, and the unprecedented delivery and installation of the longest single-piece prestressed concrete beams in not just Florida, but the United States. In the end, the design-build team will improve upon the bridge's construction schedule with minimal impacts on traffic - ultimately saving taxpayers millions of dollars and improving the mobility and safety of the intersection. Project Background Just 13 miles north of Orlando, Fla., the US 17-92/SR 436 intersection accommodates a heavy volume of commuter traffic and provides a major pipeline to motorists coming from Interstate 4 (I-4). Prior to construction, the junction of the two six-lane arterials was subject to heavy congestion and major delays, with motorists' wait time clocking in at 4 to 5 minutes. The solution was the construction of a bridge to carry US 17-92 over SR 436. The bridge is configured in three, simply supported spans with a main span of 209 ft and two approach spans of 124 ft, for a total bridge length of 457 ft. The US 17-92 flyover bridge has drastically decreased motorists' travel time since officially opening in April 2015, with drivers saving an average of 5 to 10 minutes in commute time. Motorists traveling on US 17-92 have realized the greatest improvement since they don't have to stop for the SR 436 cross traffic. Concrete vs. Steel Superstructure Originally designed as two separate continuous steel plate girder bridges, our team evaluated other options for the flyover bridge. Maintenance costs for concrete were also more economical compared to steel, which would require routine painting and more rigorous inspection. In addition, shoring towers would be needed to facilitate erection if steel girders were used, which would impede traffic on SR 436. The elimination of the shoring towers reduced traffic impacts and simplified the overall traffic control plan. Other advantages of using concrete beams over steel included improved aesthetics, reduced beam fabrication time, and reduced erection time. The benefits of concrete, coupled with lower upfront material costs, resulted in a total savings of approximately $2 million, not including long-term maintenance costs. The beams were designed with high-strength concrete (10 ksi) for increased structural capacity, which eliminated a beam line, reducing total beam costs as well as the dead load that must be carried by the PROFILE US 17-92 INTERCHANGE AT SR 436 / CASSELBERRY, FLORIDA DEPARTMENT OF TRANSPORTATION DISTRICT FIVE, OWNER BRIDGE DESIGN ENGINEER: DRMP Inc., Orlando, Fla. PRIME CONTRACTOR: The Lane Construction Corporation, Maitland, Fla. CONSTRUCTION ENGINEERING & INSPECTION: Metric Engineering, Lake Mary, Fla. PRECASTER/BEAM DELIVERY: Dura-Stress Inc., Leesburg, Fla. - a PCI-certified producer BRIDGE DESCRIPTION: Three-span simply supported bridge with a 96-in.-deep, 209-ft-long main span and two 124-ft-long approach spans for a total bridge length of 457 ft STRUCTURAL COMPONENTS: Ten 78-in.-deep Florida I-beams (FIBs) and fifteen 96-in.-deep FIBs; 8 1/2-in.-thick, cast-in-place concrete deck; cast-in-place, 6.5-ft-deep, concrete pier caps; 5 by 7 ft rectangular columns; and footings on precast concrete pilesd