The new east span of the San Francisco-Oakland Bridge features a single tower self-anchored suspension (SAS) bridge. During construction of the SAS bridge, a temporary bridge was used to support the box girders until erection of suspension cables was completed. The transfer of deck load from the temporary bridge to the suspension cables was achieved in November 2012 and the SAS bridge has become the largest of its kind in the world. The new bridge will be in service in Fall 2013.
Large diameter driven steel pipe piles were used for the temporary bridge foundations at Towers D,F and G located in San Francisco Bay. At Tower D, the large diameter steel pipe piles were driven through thin overburden into bedrock using a large Menck MHU500T hammer with a rated energy of 550 kJ. As there was no precedence in driving open-ended pipe piles into the Fanciscan Formation bedrock, challenges were faced with uncertainties in drivability, driving stresses, pile embedment in bedrock and pile capacity. These uncertainties were addressed by incorporating additional measures into the pile design, and by the use of dynamic pile monitoring during initial driving and re-strike. Pile relaxation was observed during pile installation.
At Towers F and G, setup effect was a key issue for the piles driven into the deep soft marine sediments. Drivability analyses were conducted to predict pile run, driving stresses, selection of hammer and refusal criteria. The piles were dynamically monitored during driving to estimate pile capacities. Due to the set-up effect in the Bay Mud, the piles gained up to 3.3 times the initial capacity during the re-strike and were in excess of the design capacity.
This paper presents details of the design, construction, testing, and performance of the driven pipe piles at temporary Towers D, F and G. Settlement data of the temporary tower foundations while in service confirmed the satisfactory performance of the pile foundations.
Thavaraj, T., A. Sy and M. Reyes. 2013. “Driven Pipe Pile Solutions for the Temporary Foundations at the New San Francisco-Oakland Bay Bridge,” in: 38th Annual Conference on Deep Foundations, Phoenix, Arizona, September 25-28, 2013. New York: Deep Foundations Institute.
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