Tipping Mar's Seismic Design of SFPUC Delivers Sustainable Design Goals and More

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Tipping Mar's seismic solution delivered immediate-occupancy performance, a carbon dioxide emissions savings of 7.4 million pounds, a 13th story, and $29.7 million in direct and downstream savings to San Francisco's greenest office building.

SFPUC Headquarters

How greatly Tipping Mar's seismic engineering approach contributed to the project's sustainability goals isn't immediately obvious but was crucial to the project's success as well as for direct and downstream cost savings totaling $29.7 million.

The San Francisco Public Utilities Commission's new headquarters at 525 Golden Gate Avenue is finally open. The building, designed by KMD Architects with Stevens and Associates Architects to a LEED Platinum target, is said to be one of the greenest office buildings in North America, complete with wind turbines, solar panels, and a Living Machine that recycles wastewater.

How greatly Tipping Mar's seismic engineering approach contributed to the project's sustainability goals isn't immediately obvious but was crucial to the project's success as well as for direct and downstream cost savings totaling $29.7 million.

The SFPUC building was originally designed as a steel-framed structure; however, the U.S. economic meltdown rendered such a design financially infeasible. So in 2008 Webcor Builders issued Tipping Mar a twofold challenge: to redesign the SFPUC building in concrete and to deliver immediate-occupancy-level performance. A successful concrete redesign would allow the otherwise stalled project to move ahead into construction. (An immediate-occupancy-performance level is mandated for buildings that need to remain occupiable and fully operable after a disaster like a large earthquake.)

Tipping Mar had developed an innovative hybrid lateral system involving vertically post-tensioned concrete cores, a system designed to return a building to plumb after a significant seismic event. In redesigning the SFPUC headquarters in concrete, Tipping Mar implemented the latest iteration in the firm's series of "self-centering" walls and met the performance mandate.

(For a detailed animation of the construction sequence, including the placement of the PT cores, click here.)

In addition, Tipping Mar's design solutions:
--allowed the addition of a 13th story to an originally 12-story building because of resulting lowered floor-to-ceiling heights (in turn equating to higher density--a green goal--not to mention greater usable real estate);
--from the standpoint of embodied energy, decreased the project's carbon footprint by 7.4 million pounds of carbon dioxide emissions compared to conventional concrete mixes. Tipping Mar worked with Central Concrete to design six different low-cement concrete specs for the project. In these mixes, Portland-cement replacements ranged from 40 to 70 percent, with slag and flyash as the green cementitious replacement materials. (Tipping Mar's special concrete mix designs have earned LEED innovation credits on several projects.)
--saved the project $4 million in direct structural costs, $1 million in indirect structural costs, and $24.7 million in downstream costs ($11 million on skin, $10 million on the mechanical system, and $3.7 million on the electrical system), as described in the 02/12/12 article "Tensioning Eases Stress" by Nadine Post in Engineering News Record.

It's not often that structural engineering lends impact of such magnitude and scope on whole-project and sustainability goals, but the very green San Francisco Public Utilities Commission headquarters incontrovertibly proves the possibility.

Tipping Mar was the seismic consultant on the SFPUC headquarters; SOHA Engineers is the engineer-of-record.

About Tipping Mar, Structural Engineering: Tipping Mar is a boldly innovative firm in Berkeley, CA, whose practice of structural engineering unites inventive approaches, the highest levels of technical and practical skill, a superior understanding of structural behavior, and an appreciation of good design to bring the greatest value in award-winning seismic design to clients’ projects.

A small firm of 28, Tipping Mar has nonetheless won 25 excellence in structural engineering awards from local, regional, and national structural engineering associations. A leader in sustainability-oriented design, the firm's portfolio includes 1 certified Living Building, 10 LEED Platinum and 8 LEED Gold buildings, and 5 net-zero-energy projects. In addition, Tipping Mar's low-cement concrete mixes and self-centering lateral systems have won LEED innovation credits across several projects.

Contact: Gina Tesser Phelan, gina [dot] phelan [at] tippingmar [dot] com; 510 549-1906
Tipping Mar Web site: http://www.tippingmar.com

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