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
Standards | Apr 1, 2024
New technical bulletin covers window opening control devices
A new technical bulletin clarifies the definition of a window opening control device (WOCD) to promote greater understanding of the role of WOCDs and provide an understanding of a WOCD’s function.
Adaptive Reuse | Mar 26, 2024
Adaptive Reuse Scorecard released to help developers assess project viability
Lamar Johnson Collaborative announced the debut of the firm’s Adaptive Reuse Scorecard, a proprietary methodology to quickly analyze the viability of converting buildings to other uses.
Green | Mar 25, 2024
Zero-carbon multifamily development designed for transactive energy
Living EmPower House, which is set to be the first zero-carbon, replicable, and equitable multifamily development designed for transactive energy, recently was awarded a $9 million Next EPIC Grant Construction Loan from the State of California.
Adaptive Reuse | Mar 21, 2024
Massachusetts launches program to spur office-to-residential conversions statewide
Massachusetts Gov. Maura Healey recently launched a program to help cities across the state identify underused office buildings that are best suited for residential conversions.
Multifamily Housing | Mar 19, 2024
Jim Chapman Construction Group completes its second college town BTR community
JCCG's 200-unit Cottages at Lexington, in Athens, Ga., is fully leased.
Multifamily Housing | Mar 19, 2024
Two senior housing properties renovated with 608 replacement windows
Renovation of the two properties, with 200 apartments for seniors, was financed through a special public/private arrangement.
MFPRO+ New Projects | Mar 18, 2024
Luxury apartments in New York restore and renovate a century-old residential building
COOKFOX Architects has completed a luxury apartment building at 378 West End Avenue in New York City. The project restored and renovated the original residence built in 1915, while extending a new structure east on West 78th Street.
Multifamily Housing | Mar 18, 2024
YWCA building in Boston’s Back Bay converted into 210 affordable rental apartments
Renovation of YWCA at 140 Clarendon Street will serve 111 previously unhoused families and individuals.
Adaptive Reuse | Mar 15, 2024
San Francisco voters approve tax break for office-to-residential conversions
San Francisco voters recently approved a ballot measure to offer tax breaks to developers who convert commercial buildings to residential use. The tax break applies to conversions of up to 5 million sf of commercial space through 2030.