ABSTRACT

ABSTRACT: This paper presents the design aspects for the Indian River Inlet Bridge Replacement design-build project in Delaware, USA. The new bridge will carry the SR1 Coastal Highway across the Indian River Inlet. The roadway includes four lanes of traffic with shoulders, a 12 ft sidewalk and a sand bypass system. The main span unit consists of a concrete cable-stayed bridge with a 950 ft main span and 400 ft back spans. The superstructure components include edge girders, floor beams and a concrete slab. It is supported by two vertical planes of stay cables anchored in the edge girders. The stay cables are anchored in two vertical reinforced concrete pylons using structural steel anchorage boxes to resist longitudinal tensions across the pylon section. The floor beams and edge girders are post-tensioned, as well as the top slab in the longitudinal direction in the vicinity of the transition piers and center portion of the main span. The foundations for the main span unit consist of 36 inch × 36 inch prestressed concrete piles. The deck is fixed for longitudinal movements at the North pylon and free to move at the South pylon. The deck is guided laterally at both pylons. Expansion joints are located at the transition piers and abutments. The cable-stayed spans are built on falsework over land and in cantilever with a traveling form for the portion of the main span located over the Inlet. The paper will discuss several innovative designbuild features. Some of the innovative features that will be presented include: large (36") driven piles, which proved to be the least cost and most effective foundation for the challenging soils; innovative edge girder transitions through the pylons minimized the overall footprint of the structure; single mast pylons with no cross struts; and use of cast-in-place and precast components to optimize design and construction efficiencies.