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
| May 5, 2014
Toronto residential tower to feature drawer-like facade scheme
Some of the apartments in the new River City development will protrude from the building at different lengths, creating a drawer-like "push-pull" effect.
| May 2, 2014
Norwegian modular project set to be world's tallest timber-frame apartment building [slideshow]
A 14-story luxury apartment block in central Bergen, Norway, will be the world's tallest timber-framed multifamily project, at 49 meters (160 feet).
| May 1, 2014
Tight on space for multifamily? Check out this modular kitchen tower
The Clei Ecooking kitchen, recently rolled out at Milan's Salone de Mobile furniture fair, squeezes multiple appliances into a tiny footprint.
| Apr 30, 2014
Visiting Beijing's massive Chaoyang Park Plaza will be like 'moving through a urban forest'
Construction work has begun on the 120,000-sm mixed-use development, which was envisioned by MAD architects as a modern, urban forest.
| Apr 29, 2014
Best of Canada: 12 projects nab nation's top architectural prize [slideshow]
The conversion of a Mies van der Rohe-designed gas station and North Vancouver City Hall are among the recently completed projects to win the 2014 Governor General's Medal in Architecture.
| Apr 29, 2014
USGBC launches real-time green building data dashboard
The online data visualization resource highlights green building data for each state and Washington, D.C.
| Apr 23, 2014
Developers change gears at Atlantic Yards after high-rise modular proves difficult
At 32 stories, the B2 residential tower at Atlantic Yards has been widely lauded as a bellwether for modular construction. But only five floors have been completed in 18 months.
| Apr 17, 2014
Online mapping tool helps teams determine multifamily project tax credit eligibility
Accounting and advisory firm Baker Tilly has launched a new, interactive online mapping tool that helps users determine if a business or development project may qualify for the New Markets Tax Credit or Low-Income Housing Tax Credit program.
| Apr 11, 2014
ULI report documents business case for building healthy projects
Sustainable and wellness-related design strategies embody a strong return on investment, according to a report by the Urban Land Institute.
| Apr 9, 2014
Steel decks: 11 tips for their proper use | BD+C
Building Teams have been using steel decks with proven success for 75 years. Building Design+Construction consulted with technical experts from the Steel Deck Institute and the deck manufacturing industry for their advice on how best to use steel decking.
