The new Elizabeth River Bridge, with an expected 75- to 100-year life span, is using MMFX2, a low-carbon/chromium, uncoated, corrosion-resistant, high-strength reinforcing steel. Image: City of Chesapeake, Va.
Elizabeth River Bridge reinforcement
The City of Chesapeake, Va., began construction on the new Dominion Boulevard, U.S. Route 17 project in early January 2013, which includes five new bridge structures. The largest is a four-lane, 95-foot-high, fixed-span bridge that will replace a two-lane steel bridge constructed in 1962 across the Southern Branch of the Elizabeth River.
An average of more than 33,000 vehicles travel daily across the old steel bridge — making this one of the most-traveled two-lane bridges in Virginia. The old steel bridge lifts 16 times per day, 6,000 times a year, on average. Each lift takes roughly 10 minutes, which equates to 42 days a year that the bridge cannot be crossed. The new Elizabeth River Bridge will not have these congestion issues because of the expansion to four lanes and being at a height to allow ships to pass beneath.
Originally specified to use stainless steel as the corrosion resistant reinforcement (CRR) material for the concrete deck, parapets, sidewalks, and approach slabs — as dictated by the VDOT IIM-S&B-81.4 — the City of Chesapeake saw an opportunity to save money without sacrificing quality and structural capacity. It submitted a waiver request to the Virginia Department of Transportation (VDOT) to allow use of MMFX2, a low-carbon/chromium reinforcing steel. MMFX2 is an uncoated, corrosion-resistant, high-strength rebar from MMFX Steel Corporation.
With the approval of the waiver, the City of Chesapeake is accepting responsibility for all future maintenance; it expects the bridge to have the same 75 to 100 years of life. The $345.2 million Dominion Boulevard Project is 100-percent publicly funded by the City of Chesapeake, supported through a Virginia transportation infrastructure bank loan, toll revenue bonds, Virginia state and federal funds, and existing reserves and earnings. A $1 toll using a fully automated E-ZPass toll collection system will be put into effect once construction is completed.
Once construction is completed on the first two-lane span (5,982 feet) of the Elizabeth River Bridge, traffic will be routed to the new span and the old steel bridge will be demolished. A second two-lane span (5,262 feet) will then be constructed with an anticipated completion date in early 2017.
The improved Dominion Boulevard and the existing Chesapeake Expressway will together form the Chesapeake Transportation System (CTS). The CTS will operate as a single facility, with operations being combined to reduce redundancy and overhead.
In 2010, VDOT became the first department of transportation in the United States to institute a CRR standard specifying the use of MMFX2 reinforcing steel based on its own testing. Since then, VDOT has fully implemented its CRR policy for all new bridge designs.
Information provided by MMFX Steel Corporation of America (www.mmfx.com)
DBIA Florida recognizes I-4 Bridges project
The Design-Build Institute of America’s (DBIA) Florida Region selected the I-4 Bridges Spanning Reedy Creek Project in Osceola County, Fla., as the state’s Design-Build Project of the Year in the Transportation Category. Designed by Gannett Fleming and built by The Lane Construction Corporation, the project was evaluated on criteria including design-build best practices, design and quality, sustainability, safety, schedule, and cost performance.
The Florida Department of Transportation District 5 undertook The I-4 Bridges Spanning Reedy Creek Project after inspections revealed that the twin bridges were scour critical. The Lane Construction/Gannett Fleming design-build team provided the final design and built a supplemental substructure system for the bridges. Gannett Fleming’s design solution called for crutch bents at all intermediate bent locations to transfer load paths to new and deeper foundations. The design minimized traffic disruptions and environmental impacts. It allowed the project to be completed at a significantly reduced cost and on an accelerated schedule.
Information provided by Gannett Fleming (www.gannettfleming.com)
3D modeling for road and floodplain improvements
In early 2014, the City of San Marcos, Texas, will begin construction on a road improvement project to enhance safety and mobility in the project area while improving conveyance of storm and floodwaters. The project consists of widening Hunter Road, adding bicycle or multi-use paths, and replacing a low-water culvert crossing over Purgatory Creek (where flooding frequently closes this major thoroughfare) with a bridge designed to allow the roadway to remain passable during a 25-year flood event. Kimley-Horn and Associates led the design team as prime consultant; Halff Associates provided hydraulic (floodplain) analysis and design for the project team.
Project engineers used model-based Autodesk software, including Autodesk AutoCAD Civil 3D and Autodesk AutoCAD software, to help analyze and develop hydraulic design strategies that will control flooding of the road near the creek and help the city reclaim previously unsalable floodplain properties. Model-based design helped the team quickly iterate and simulate how changing variables, such as roadway profile, channelization length, and bridge opening width affects the floodplain. A dynamic project model that automatically adjusted whenever these variables were changed enabled the team to evaluate many geometric configurations quickly and efficiently.
This effort helped the design team demonstrate that the vertical profile of the roadway could be lowered relative to the schematic design and still eliminate the upstream flooding of existing homes and businesses, providing the city substantial benefits. Furthermore, the proposed design would remove previously undevelopable properties from the floodplain, further bolstering the economic benefits of constructing the roadway project.
Model-based design workflow tools allowed engineers to efficiently import and export floodplain models and surfaces to prepare floodplain maps quickly. Image: Halff Associates
The design team developed a 3D project model that included existing survey conditions and proposed designs for the road, bridge, grading, and channelization. With each design iteration, the model was exported to specialized hydraulic analysis software to perform hydraulic calculations and simulate the precipitation runoff. This iterative process resulted in a proposed project design that allows for adequate interim flood conveyance, and includes appropriate grade for a bikeway clearance, minimal interim jurisdictional waters disturbance, and appropriate ultimate conveyance for future channelization and floodplain reclamation. Model-based design workflow tools allowed engineers to efficiently import and export floodplain models and surfaces to prepare floodplain maps quickly and to communicate designs with the city staff and public stakeholders effectively.
Information provided by Autodesk (www.autodesk.com)
Submit news and photos of planned, ongoing, or recently completed projects and research to Bob Drake at email@example.com.