Bridges Coast to Coast
Apart from being quite dissimilar in the respective structural types and methods of execution, these two bridges are also separated by being located at opposite coasts:
- NC 12 Rodanthe bridge project over Pamlico Sound in North Carolina, East Coast;
- McKinley Overhead steel arch bridge, over railways, a canal and a street in the city of Corona, California, West Coast.
The first structure consists of a long prestressed concrete multi-span coastal viaduct, about 13,000 ft long, with a “jug-handle“ configuration, while the second structure is located in an inland semi-urban environment and consists of a steel tied arch with a network-basket configuration with little more than 300 ft, with a single span.
What is common to both structures, making the coast-to-coast connection, is that both were designed to be on a fast track construction schedule, using ABC techniques, and both incorporate innovative methods of construction and service characteristics.
McKinley Overpass: Innovative Steel Tied Arch
Jose C. Calisto da Silva, P.E., MSc., M.ASCE - Director Bureau of Complex Calculations, BCA, Inc.
Mahsa Farzad, PhD, P.E. - Staff Engineer, BCA, Inc.
Austin Emrich, BSc - Assistant Engineer, BCA, Inc.
Benjamin Chan, MSc - Assistant Engineer, BCA. Inc.
The McKinley Street Overhead will be a steel network tied-arch bridge, consisting of a single span, approximately 290- feet long, with a basket configuration. The two arch ribs that will support the span, will lie on planes inclined 16º towards the center of the bridge. The bridge will be constructed in a staging area, simultaneously with the substructure, then moved into place with the aid of self-propelled modular transporters (SPMTs). For decreasing the overall demand of the bridge for the seismic actions, especially in what concerns the site connections, all bolted, a novel system of seismic units was devised. This system consists of 6 units, four of the PSD type, acting as shear keys up to a predetermined force value, and as viscous dissipators above that force; the other two units are VFDs, which for slow movements act as free expanding or contracting, while for sharp movements, such as wind gusts, or seismic actions, act as viscous dissipators. There are two transverse PSD units at the center of the bent caps, and in the longitudinal direction there are two PSDs at the South abutment, and two VFDs at the North abutment, thus allowing a configuration of fixed on one side and movable on the other for thermal actions, shrinkage and traffic loads, allowing the participation of both abutments in almost equal terms, by calibration, in the resistance to the seismic action in the longitudinal direction. Bearings sliding in both directions were used at the four support corners of the arch.
David B. Peterson, P.E., F.ASCE - Director, Structures, RK&K
On January 3, 2017, the North Carolina Department of Transportation (NCDOT) awarded the 2.5‐mile long, $145.3 million NC-12 Rodanthe bridge project over Pamlico Sound to the Flatiron Constructors and RK&K design‐build team. The design and construction of this unique “jug-handle” bridge on North Carolina’s scenic coast was a very challenging project. It was opened to traffic in June 2022 as the ninth longest bridge in North Carolina.
Due to the geometry of the bridge, environmental limitations, and an accelerated schedule, our team developed a specific construction technique that would minimize the footprint of impacts to the environment. This method was an innovative “Advancing Rail System” that allowed gantry and platform cranes to straddle the newly constructed bridge, substantially decreasing environmental impacts. While the new bridge is nearly 13,000 feet long, the rail system was only 3,000 linear feet at any one time, as it used previously constructed sections of the bridge for access. With a horizontal alignment that narrowly bypasses a historic sunken ship, the new two‐lane bridge is 40 feet wide with bicycle safe rails and has a minimum of 17 feet of clearance above mean sea level (MSL). The superstructure consists of 72” Florida I-Beams (FIBs) in the tangent section of the main bridge. The total number of 54” diameter precast prestressed cylinder piles is 294 with a total length of installed driven pile of approximately 41,500 linear feet. The concrete piles were driven between 80 feet to 135 feet deep into the soil of Pamlico Sound.