Work has begun to construct temporary piers to support the I-43 Leo Frigo Bridge. Pier 22 of the bridge settled approximately 2.5 feet in late September/early October. The new piers are being constructed by Lunda Construction. The goal of the structures is to prevent any additional settlement of the deck. The bridge will remain closed pending a permanent solution. The ENR article did not list what the piers will be founded on, but the conceptual drawings available from WisDOT seem to show drilled shaft foundations. [Source: ENR: Engineering News Record. Image: WisDOT via ENR]
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San Francisco Millennium Tower Has Settled 16 Inches
The residential high-rise Millennium Tower in San Francisco has settled a total of 16 inches since opening, 2 inches deferentially. A spokesman for the tower owner blames the settlement on the excavation next door for the Transbay Transit Center, a $2.4 billion dollar project being constructed 60 feet underground.
However, the Transbay Joint Powers Authority (Transbay) hired geotechnical firm Arup in 2010. Their initial report indicated that the tower had already settled 10 inches by the time excavation began for the Transit center. Arup seems to have been tasked with design, installation, and perhaps monitoring of a geotechnical monitoring program, some information on the scope is available in a 2012 presentation given by Arup available on the Transbay website.
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