Klohn Crippen Berger (KCB) was retained by the American Bridge/Fluor JV to serve as lead construction engineers for the largest self-anchored suspension bridge in the world. The 700 m-long suspension deck system consists of twin steel orthotropic box girders. Construction required the design of twin temporary steel trusses to support the box girders during deck erection until loads were transferred to the suspension cables. The temporary trusses were supported by seven steel frame towers, which were designed as state-of-the-art “tubular” eccentrically braced frames using steel box sections. A 165 m-tall temporary steel erection tower was designed to erect the single permanent steel suspension tower in four separate lifts.
The falsework was in service for a period of 3-4 years, a relatively long time for temporary structures. Given the seismic risks in the Bay area, the falsework was designed for substantial seismic and vessel impact loading. Foundation types included micropile foundations on bedrock, cast-in-drilled-hole concrete caissons, and deep driven steel piles in soft marine clays in 25 m-deep water. Fast track design and construction was required to meet an aggressive schedule. The design was initiated mid-2006 and both the design and construction of 25,000 tonnes of temporary steel work was completed by November 2009. The bridge opened in 2013.
- Structural design of temporary towers and trusses
- Geotechnical design for tower foundations
- Staged erection analysis of the temporary work and deck and tower segments
- Design for seismic and ship impact loading