Since completing construction, the 58-story Millennium Tower has become San Francisco’s most infamous building.
The tower is founded on piles driven through soft, compressible clay soils deposited by San Francisco Bay and extending into a dense sand layer over ancient marine deposits of clays, silts, and sands, according to engineering firm Simpson Gumpertz & Heger (SGH). The building’s weight and nearby construction projects caused consolidation and lateral displacement of the soils, which led to the tower settling more than 17 inches and tilting four inches across its footprint. Needless to say, this tilting began to worry residents and thrust the building into the national spotlight.
After a two-year permitting and approval process, a fix is finally set to move forward with SGH as the engineer-of-record. SGH evaluated whether the building required structural reinforcement to restore its integrity or seismic resistance to original levels. SGH lists the outcomes of the evaluation as:
– Developed detailed nonlinear models of the structure, its foundations, and underlying soil to simulate the effects of settlement and tilting
– Conducted detailed nonlinear analyses of the structure’s response to earthquake shaking
– Designed an underpinning retrofit for the structure, consisting of jacking approximately 20% of the building’s weight onto new foundation piles (52 piles to be exact) extended to rock along the structure’s north and west sides
The fix will prevent any future settlement and reverse the current tilting over time. The project is expected to begin this fall.
Related Stories
| Aug 11, 2010
Bovis Lend Lease, Webcor among nation's largest multifamily contractors, according to BD+C's Giants 300 report
A ranking of the Top 50 Multifamily Contractors based on Building Design+Construction's 2009 Giants 300 survey. For more Giants 300 rankings, visit http://www.BDCnetwork.com/Giants
| Aug 11, 2010
Looney Ricks Kiss Architects wins industry honors for mixed-use, multifamily, and residential designs
Looney Ricks Kiss Architects won four Aurora Awards for its architectural designs during the recent Southeast Building Conference in Orlando, including a Grand Aurora Award for a Mixed Use Multi Family community located in the West Village area of Dallas.
| Aug 11, 2010
Jacobs, Arup, AECOM top BD+C's ranking of the nation's 75 largest international design firms
A ranking of the Top 75 International Design Firms based on Building Design+Construction's 2009 Giants 300 survey. For more Giants 300 rankings, visit http://www.BDCnetwork.com/Giants
| Aug 11, 2010
See what $3,000 a month will get you at Chicago’s Aqua Tower
Magellan Development Group has opened three display models for the rental portion of Chicago’s highly anticipated Aqua Tower, designed by Jeanne Gang. Lease rates range from $1,498 for a studio to $3,111 for a two-bedroom unit with lake views.
| Aug 11, 2010
Architecture Billings Index flat in May, according to AIA
After a slight decline in April, the Architecture Billings Index was up a tenth of a point to 42.9 in May. As a leading economic indicator of construction activity, the ABI reflects the approximate nine to twelve month lag time between architecture billings and construction spending. Any score above 50 indicates an increase in billings.
| Aug 11, 2010
Construction employment declined in 333 of 352 metro areas in June
Construction employment declined in all but 19 communities nationwide this June as compared to June-2008, according to a new analysis of metropolitan-area employment data released today by the Associated General Contractors of America. The analysis shows that few places in America have been spared the widespread downturn in construction employment over the past year.
| Aug 11, 2010
Jacobs, Hensel Phelps among the nation's 50 largest design-build contractors
A ranking of the Top 50 Design-Build Contractors based on Building Design+Construction's 2009 Giants 300 survey. For more Giants 300 rankings, visit http://www.BDCnetwork.com/Giants
| Aug 11, 2010
Arup, SOM top BD+C's ranking of the country's largest mixed-use design firms
A ranking of the Top 75 Mixed-Use Design Firms based on Building Design+Construction's 2009 Giants 300 survey. For more Giants 300 rankings, visit http://www.BDCnetwork.com/Giants
