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
Smart Buildings | Jan 7, 2014
9 mega redevelopments poised to transform the urban landscape
Slowed by the recession—and often by protracted negotiations—some big redevelopment plans are now moving ahead. Here’s a sampling of nine major mixed-use projects throughout the country.
| Jan 3, 2014
World’s tallest vegetated façade to sprout in Sri Lanka [slideshow]
Set to open in late 2015, the 46-story Clearpoint Residences condo tower will feature planted terraces circling the entire structure.
| Dec 31, 2013
BD+C's top 10 stories of 2013
The world's tallest twisting tower and the rise of augmented reality technology in construction were among the 10 most popular articles posted on Building Design+Construction's website, BDCnetwork.com.
| Dec 27, 2013
$1 billion 'city within a city' development approved by Coachella, Calif., city council
The mega development includes 7,800 homes, a retail center, office space, and nearly 350 acres of open space.
| Dec 23, 2013
MBI commends start of module setting at B2, world's tallest modular building
The first modules have been set at B2 residential tower at Atlantic Yards in New York, set to become the tallest modular building in the world.
| Dec 20, 2013
Can energy hogs still be considered efficient buildings? Yes, say engineers at Buro Happold
A new tool from the engineering firm Buro Happold takes into account both energy and economic performance of buildings for a true measure of efficiency.
| Dec 13, 2013
Safe and sound: 10 solutions for fire and life safety
From a dual fire-CO detector to an aspiration-sensing fire alarm, BD+C editors present a roundup of new fire and life safety products and technologies.
| Dec 10, 2013
16 great solutions for architects, engineers, and contractors
From a crowd-funded smart shovel to a why-didn’t-someone-do-this-sooner scheme for managing traffic in public restrooms, these ideas are noteworthy for creative problem-solving. Here are some of the most intriguing innovations the BD+C community has brought to our attention this year.
| Dec 4, 2013
First look: Dubai's winning bid for World Expo 2020 [slideshow]
Dubai has been chosen as the site of the 2020 World Expo. HOK led the design team that developed the master plan for the Expo, which is expected to draw more than 25 million visitors from October 2020 through April 2021.
| Nov 27, 2013
Exclusive survey: Revenues increased at nearly half of AEC firms in 2013
Forty-six percent of the respondents to an exclusive BD+C survey of AEC professionals reported that revenues had increased this year compared to 2012, with another 24.2% saying cash flow had stayed the same.