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
Market Data | Dec 29, 2020
Multifamily transactions drop sharply in 2020, according to special report from Yardi Matrix
Sales completions at end of Q3 were down over 41 percent from the same period a year ago.
Multifamily Housing | Dec 16, 2020
What the Biden Administration means for multifamily construction
What can the multifamily real estate sector expect from Biden and Company? At the risk of having egg, if not a whole omelet, on my face, let me take a shot.
Giants 400 | Dec 16, 2020
Download a PDF of all 2020 Giants 400 Rankings
This 70-page PDF features AEC firm rankings across 51 building sectors, disciplines, and specialty services.
Multifamily Housing | Dec 4, 2020
The Weekly show: Designing multifamily housing for COVID-19, and trends in historic preservation and adaptive reuse
This week on The Weekly show, BD+C editors spoke with leaders from Page & Turnbull and Grimm + Parker Architects about designing multifamily housing for COVID-19, and trends in historic preservation and adaptive reuse
Giants 400 | Dec 2, 2020
2020 Multifamily Sector Giants: Top architecture, engineering, and construction firms in the U.S. multifamily building sector
Clark Group, Humphreys & Partners Architects, and Kimley-Horn head BD+C's rankings of the nation's largest multifamily building sector architecture, engineering, and construction firms, as reported in the 2020 Giants 400 Report.
Smart Buildings | Nov 20, 2020
The Weekly show: SPIRE smart building rating system, and pickleball court design tips
The November 19 episode of BD+C's The Weekly is available for viewing on demand.
AEC Tech | Nov 12, 2020
The Weekly show: Nvidia's Omniverse, AI for construction scheduling, COVID-19 signage
BD+C editors speak with experts from ALICE Technologies, Build Group, Hastings Architecture, Nvidia, and Woods Bagot on the November 12 episode of "The Weekly." The episode is available for viewing on demand.
Multifamily Housing | Nov 11, 2020
San Jose affordable housing project will feature a mass timber frame
SERA Architects and Lendlease will design and build the project.
Multifamily Housing | Oct 30, 2020
The Weekly show: Multifamily security tips, the state of construction industry research, and AGC's market update
BD+C editors speak with experts from AGC, Charles Pankow Foundation, and Silva Consultants on the October 29 episode of "The Weekly." The episode is available for viewing on demand.
