SFMTA Central Subway Chinatown Station

Construction for this new station will require the deepest building excavation ever in the City of San Francisco in the middle of San Francisco’s Chinatown neighborhood.

Customized Solution

  • The new, 100,000 s.f. Chinatown Subway Station will extend Muni-light rail service from South of Market to Chinatown. The station includes a mined cavern with platform for trains, as well as the concrete station structure that extends 100 feet below ground. The project includes retail at the street level and is being designed for future rooftop vertical development opportunities.
  • Perhaps the greatest challenge was minimizing obstruction to traffic above during all phases of construction. The fast construction schedule also required a complicated design solution with a bottom-up construction approach.
  • Underground construction required minimizing ground settlement in order to maintain the foundations of numerous existing historic structures above despite the massive volume of the excavation.
  • For current construction updates, please visit the Central Subway Chinatown Blog.

San Francisco City Hall Seismic Retrofit

As the Prime Consultant for the largest base isolation retrofit project in its time, Forell/Elsesser developed and implemented an unprecedented base isolation retrofit solution, directed 13 sub-consultants, and coordinated planning and sequencing of the retrofit construction of one of San Francisco’s greatest treasures.

Customized Solution

  • Built in 1912, the 550,000 s.f., 4-story City Hall building sustained damage from the 1989 Loma Prieta earthquake, necessitating repairs and a seismic retrofit. Base isolation was selected as the best solution because it is the most cost-effective solution and it allows for minimum intrusion to the ornate historic building, all while providing maximum seismic protection.
  • In addition to base isolation, the project included installation of concrete shear walls around the light courts, and steel bracing at the dome/drum level.
  • Forell/Elsesser assisted the City with obtaining funding for this project, and facilitated the extensive review process from federal, state, and local agencies.
  • The large scale and breadth of this retrofit and repair project required careful planning and sequencing during construction to avoid damage to the precious historic fabric of the building and to avoid structural instability in the event of an earthquake during construction.

 

AOC Mono County (Mammoth Lakes) Courthouse

Designed to withstand the heavy Mammoth snows as well as a large earthquake, this much needed courthouse was completed under budget and on schedule despite strict building guidelines.

 

Customized Solution

  • With two full courtrooms, a hearing room, administrative offices, and additional counters to serve the public, the completion of this new structure will improve access and services to the community.
  • Perhaps the greatest challenge of this project was the interaction between engineering for seismic activity and snow, as the building needed to withstand both, potentially at once. With the addition of a window wall framed with architecturally exposed steel in the lobby, this was no simple task. Therefore, the roof is designed to withstand 400 lbs. per sf of snow—a massive weight. The steel framed main building and garage are equipped with buckling restrained braced frame walls for seismic strength.
  • The project team was able to navigate the local and AOC construction guidelines, and successfully design for both. The project was completed under budget and on schedule.

 

Portola Valley Town Center

This five-building town center located near the San Andreas Fault employed sustainable design practices wherever possible, achieving LEED Platinum Certification.

 

Customized Solution

  • As sustainable design was essential to the project, Forell/Elsesser worked closely with the architect to creatively blend structural and architectural elements for the most efficient, expressive design possible. PV solar paneling, reclaimed materials from the previous Town Hall, reused timber from the site, FSC approved lumber, and recycled (slag) concrete were among the sustainable design elements used throughout the project.
  • Forell/Elsesser worked diligently with the contractor, ensuring that both sustainability goals and construction schedule requirements would be met
  • Due to the close proximity of the San Andreas Fault, the structural materials used throughout the center are proven to increase seismic safety. The multiple-sloped roof profiles also required special attention and were designed to withstand large seismic events.
  • The center includes a Library, Town Hall, Community Hall with kitchen, activity rooms, and an assembly area. The Town Hall seismic system was designed to provide better performance than required by code standards with the intention that it could potentially serve as an Emergency Operations Center after a major earthquake.

 

Pasadena City Hall Seismic Retrofit

The LEED Gold Certified rehabilitation of this 1927 historic landmark included cost-effective seismic isolation, modernization of plumbing and electrical systems, and the addition of a new building with a connecting underground tunnel, all without altering the building’s historic integrity.

 

Customized Solution

  • The City of Pasadena had two primary goals for the seismic upgrade of their City Hall: to limit the intrusion of the new seismic upgrade into the significant historic elements of the building and to minimize the amount of damage anticipated after a major earthquake. To address both needs, friction pendulum isolators were placed between the foundation and basement. They were positioned on an off-grid system with one isolator in the center of four columns, thus supporting the entire square rather than one isolator per column. This innovative technique both minimized costs and increased construction efficiency.
  • Forell/Elsesser benchmarked performance analysis against data obtained from the Northridge earthquake, showing that much of the historic non-structural elements were sound and did not require repair, thus keeping costs down.
  • Shear walls were installed on the East end of the building’s wings, and a replacement of the deteriorating arcade with a utility tunnel running underneath, structurally tied the building’s two wings together. The project also included the modernization of Mechanical, Electrical and Plumbing systems, necessitating the redesign of structural systems to accommodate the new weight and space requirements of these energy-efficient additions.