Earthquake Resistance Through Pile Foundation + SidePlate Technology

85 Bluxome

Positive Impact on the Environment and Tenants 

85 Bluxome Street | San Francisco, CA
Mixed Use | 57,000 square feet
Principal in Charge:  Mark A. Moore
Project Manager:  Ryan Bogart

Today, San Francisco consists of a nearly square-shaped landmass of nearly 49 square miles, but it wasn’t always quite this large. Expansion into the Bay over the past 150 years has kept our city growing, and designing structures to be stable in these less-than-ideal soil conditions has been a continuing challenge for structural engineers.

Our recent project at 85 Bluxome Street, a five-story modern building in the south of Market neighborhood, included the challenges associated with deep foundations in Bay Mud as well as seismic and sustainability concerns for which San Francisco is famously on the forefront.

First, we had to secure a solid foundation.

Imagine a bucket of sand that has been saturated with water. If you were to press down on the sand with your palm, it would act like a relatively stable solid. Now, imagine shaking the bucket hard enough and long enough so that the sand becomes loose and pourable, like a liquid. That’s precisely what can happen in an earthquake—what seems like a solid foundation can become anything but in a matter of seconds. The process is known as “liquefaction,” and it’s a real concern when building on reclaimed land from the Bay.

To ensure that 85 Bluxome would stand up to Mother Nature, we designed a deep pile foundation. Piles reach deep into the earth and transfer the weight of a building to more stable soil or bedrock. Many types of piles are available, but the system chosen for this project—drilled displacement piles—consist of steel pipes with a screw-like tip that are quietly drilled into the loose Bay Mud. The steel pipe is then filled with concrete and connected to the base of the structure with a reinforcing cage, making for a stable, reliable support structure.

Next, we focused on seismic sway.

Given the seismic activity in this beloved city, we also need to routinely contend with the potential for swaying buildings. In space-constrained cities like San Francisco, architects often design buildings that extend to the edge of property lines in order to deliver maximum leasable space to the tenant. That seems like a reasonable solution until an earthquake strikes, and buildings start moving side-to-side, or swaying.

To handle the sway, we added stiffness to the structure by using the proprietary SidePlate moment frame lateral force-resisting system. The combination of a deep pile foundation and SidePlate technology was designed to greatly reduce the impact an earthquake will have on the structure while delivering maximum leasable space to the owner.

Positive impact through LEED Gold rating and WELL certification.

The developers for 85 Bluxome sought a LEED Gold rating, and on top of that, are among the first to seek WELL certification, an emerging concept that buildings should have a positive impact on their dwellers or tenants. More specifically, a WELL Building Certified™ spaces can help create a built environment that improves the nutrition, fitness, mood, sleep patterns and performance of its occupants. 85 Bluxome will offer many amenities including a workout room, locking bike racks, locker rooms with showers, a rooftop deck, and office space with varying levels of privacy that are designed to promote collaboration and flexibility.

85 Bluxome Street uses modern structural systems to provide a healthy, open space for its tenants, and brings new life to this piece of land that was once part of the Bay. We are incredibly proud to have been part of the design team of this progressive and project.