To accomplish the tremendous task of replacing the east spans of the Bay Bridge from Oakland to Yerba Buena Island, Caltrans initiated a plan to remove portions of the existing Bay Bridge and shift the eastbound and westbound traffic off the existing structure and onto a temporary detour structure known as the Temporary Bypass Structure (TBS). The TBS, which was 1066 feet in length and 170 feet at its highest point, created the room needed for the new Bay Bridge to enter the tunnel in its current alignment.
TRC prepared the final design plans, specifications and estimate for the TBS Viaduct - a double deck steel truss, consisting of five spans. Each span was approximately 250 feet in length and carried five lanes of traffic in each direction on two levels of bridge decks. The spans were built on falsework that was removed after the completion of each truss span. The completed project incorporated around 9000 tons of structural steel.
Located in a zone of high seismic activity that is in close proximity to two nearby faults (San Andreas and Hayward), TRC seismic experts developed a 3-D structural analysis model of the double deck steel truss viaduct as well as conducted a response spectrum analysis in compliance with Caltrans seismic code. TRC also provided a review of the working drawings including steel fabrication and erection plans, shop details, the Fracture Control Plan for fracture critical members (FCM), the stay-in-place metal deck forms, the 10’ diameter cast-in-drilled-hole (CIDH) pile placement and mitigation plans, the tie-down plans, and the joint seal assembly; as well as performed on-site inspection and provided sound engineering consultation and solutions to this complex project during construction. Other tasks included reviewing and analyzing the contractor’s CPM schedule, review of RFIs, preparation and negotiation of change orders, and evaluation of strategies to resolve disputes.
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