Resilient Design at 85 Bluxome

When the goal of maximizing leasable space also yields resilience; the story of San Francisco’s first USRC-rated building

Problem Statement

With San Francisco office space hitting record high prices, maximizing leasable area is one of the top priorities of commercial developers after the safety and comfort of occupants. 85 Bluxome was no exception as Bluxome Partners, LLC set out to build a modern, stylish, Class A office space in San Francisco’s South of Market (SOMA) neighborhood. In addition to maximizing floor area, Bluxome Partners also sought a design and function that would protect their tenants from the region’s infamous seismic activity as well as ensure the ability to recover quickly from the next big earthquake.

How ZFA Added Value

More Leasable Floor Area + Better Resilience

The solution to maximizing square footage and providing an earthquake-resilient design was able to be addressed in a single structural system: a high-performing proprietary SidePlate moment frame system. This solution provided a stiff seismic force-resisting system that simultaneously:

      • reduced building drift (a.k.a. horizontal movement from seismic forces) to allow the building to be pushed as close to the property lines as possible, increasing valuable floor space on each story, and
      • provided a stiffer-than-required system that improved structural performance in an earthquake.

With careful accounting, the return on investment for this strategy was clear; the added square footage was of far greater value than the cost of the structural steel used to achieve it. Additional attention to detailing of stairs and anchorage of mechanical equipment was performed to ensure cohesive performance between structural and non-structural systems. This, in addition to the increased building stiffness, not only provided structural performance above what the building code requires, it also contributed to the quantitative resilience assessment that resulted in achieving a USRC Gold rating.

Achieving USRC Gold

85 Bluxome is the first building in San Francisco to receive a USRC rating. It was awarded a USRC Gold Rating for achieving five stars for safety and four stars for both damage and recovery. USRC ratings are provided following a building analysis performed with specialized, research-based software. Detailed information about structural, mechanical, and non-structural systems are input, and a complex risk assessment is performed to assess a building’s expected repair costs, recovery time, and casualties. USRC-certified engineers then audit each assessment and award buildings with a Platinum, Gold, Silver, or Certified (code-level) Rating.

The first round of USRC review for 85 Bluxome resulted in a Silver Rating—five stars for safety but only three stars for damage and recovery. As founding USRC members, ZFA engineers have a thorough understanding of how each metric is evaluated and rated. Upon review of the initial evaluation, it quickly became clear that the three-star ratings were overly conservative and that four-star ratings were more appropriate for these two metrics. With minor updates to the evaluation criteria to better reflect the performance of the structure and resulting effects on occupants, 85 Bluxome received an appropriate rating of USRC Gold.

The Result

By listening to and understanding client concerns, ZFA was able to deliver a building that provided the best value to the client and occupants via maximum floor area and superior earthquake resilience. Additionally, utilizing an intimate understanding of seismic risk analysis and USRC rating requirements, a USRC Gold Rating was achieved, documenting the increased expected performance of the structure, which includes functional recovery from a major earthquake in less than one week.

This building is a great example of the synergy that can exist when multiple goals are aligned and everyone—owners, tenants, and communities—wins.