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STRUCTURES The Bridge Development Report (BDR) performed during the Initial Engineering Phase will establish the basic parameters that will affect the work in the Final Engineering Phase. The BDR will consider various bridge elements and compare them for viability, durability, constructability, maintainability, and cost. Examples of BDR element comparisons include: • Main Span Structural System Elements - o Florida U-Beams (FUB) - FUBs are preferred choice from preliminary calculations and design concepts and are featured in the narrative below o Florida I-Beams (FIB) - FIBs introduce more elements to erect, more diaphragms to cast, have less torsional capacity, and add visual clutter with the additional beam lines beneath. o Steel Box or I-girders - With the highly corrosive oceanfront environment, steel superstructures need coating systems that require costly maintenance. Maintenance activities are costly and disruptive to traffic along Collins Ave. • Foundation Elements - o Drilled Shafts - installation of shaft casings increase construction vibration risk to adjacent high value properties o Augercast piles - minimal installation vibration The following discussion previews the BDR process and presents solutions resulting from our initial screening of known project issues. Final recommendations will be documented for City and FDOT review, comments, and approval prior to proceeding to Final Engineering phase. Main Structural System The structural system needs to solve the following requirements to satisfy the functionality and geometry of the Bridge Park: • Complex Irregular Plan Geometry - requires a superstructures system that can accommodate width changes without excessive cost or complicated details • Grade Separated Park Areas - requires a superstructure cross section that can accommodate different elevations without excessive structural depth • Single Span - requires a superstructure system that spans the entire Collins Avenue corridor We propose the use of a “spine and rib” system with a spine of consisting of three redundant, Florida U Beams (FUBs) and continuous transverse concrete ribs of varying lengths. The spine and rib system provides structural redundancy, weight efficiency, geometric versatility, durability, constructability, and low-cost relative to other systems such as heavy segmental post-tensioned systems or high maintenance steel. It is critical to provide a simple and redundant structural system to support the complex functionality. It is equally important to develop a structural system that is safely constructible and durable to protect the City’s investment. D-12