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
| Feb 5, 2014
7 towers that define the 'skinny skyscraper' boom [slideshow]
Recent advancements in structural design, combined with the loosening of density and zoning requirements, has opened the door for the so-called "superslim skyscraper."
| Feb 4, 2014
Must see: Student housing complex made with recycled shipping containers
Architect Christian Salvati's new structure is just the first step in bringing shipping container construction to New Haven, Conn.
| Jan 29, 2014
Historic church will be part of new condo building in D.C.
Sorg Architects unveiled a design scheme for 40 condos in a six-story building, which will wrap around an existing historic church, and will itself contain four residential units.
| Jan 28, 2014
First Look: BIG's Honeycomb building for Bahamas resort [slideshow]
BIG + HKS + MDA have unveiled the design for the new Honeycomb building and adjacent plaza in The Bahamas – a 175,000-sf residential facility with a private pool on each balcony.
| Jan 28, 2014
2014 predictions for skyscraper construction: More twisting towers, mega-tall projects, and 'superslim' designs
Experts from the Council on Tall Buildings and Urban Habitat release their 2014 construction forecast for the worldwide high-rise industry.
| Jan 28, 2014
16 awe-inspiring interior designs from around the world [slideshow]
The International Interior Design Association released the winners of its 4th Annual Global Excellence Awards. Here's a recap of the winning projects.
| Jan 24, 2014
Urban Land Institute, Enterprise outline issues in rental housing shortage: Report
Bending the Cost Curve: Solutions to Expand the Supply of Affordable Rentals outlines factors that impede the development of affordable rental housing – causing the supply in many markets to fall far short of the demand.
| Jan 22, 2014
SOM-designed University Center uses 'sky quads,' stacked staircases to promote chance encounters
The New School's vertical campus in Manhattan houses multiple functions, including labs, design studios, a library, and student residences, in a 16-story building.
| Jan 13, 2014
Custom exterior fabricator A. Zahner unveils free façade design software for architects
The web-based tool uses the company's factory floor like "a massive rapid prototype machine,” allowing designers to manipulate designs on the fly based on cost and other factors, according to CEO/President Bill Zahner.
| Jan 8, 2014
Strengthened sprinkler rules could aid push for mid-rise wood structures in Canada
Strengthened sprinkler regulations proposed for the 2015 National Building Code of Canada (NBCC) could help a movement to allow midrise wood structures.