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
| 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.
| Nov 27, 2013
Wonder walls: 13 choices for the building envelope
BD+C editors present a roundup of the latest technologies and applications in exterior wall systems, from a tapered metal wall installation in Oklahoma to a textured precast concrete solution in North Carolina.
| Nov 26, 2013
Construction costs rise for 22nd straight month in November
Construction costs in North America rose for the 22nd consecutive month in November as labor costs continued to increase, amid growing industry concern over the tight availability of skilled workers.
| Nov 25, 2013
Building Teams need to help owners avoid 'operational stray'
"Operational stray" occurs when a building’s MEP systems don’t work the way they should. Even the most well-designed and constructed building can stray from perfection—and that can cost the owner a ton in unnecessary utility costs. But help is on the way.
| Nov 19, 2013
Top 10 green building products for 2014
Assa Abloy's power-over-ethernet access-control locks and Schüco's retrofit façade system are among the products to make BuildingGreen Inc.'s annual Top-10 Green Building Products list.
| Nov 15, 2013
Greenbuild 2013 Report - BD+C Exclusive
The BD+C editorial team brings you this special report on the latest green building trends across nine key market sectors.
