Structures / 181 Fremont Tower
- Jason Krolicki
The 181 Fremont Tower is the tallest mixed-use building on the West Coast of the United States. The 56-story tower is 820 ft tall, features 67 luxury residences and 435,000 square feet of commercial space. There is an amenity floor with a fitness center, lounge, and a double-height outdoor terrace that separates the residential and commercial levels. The tower also has a pedestrian bridge on the seventh level that connects to the adjacent Transit Center’s rooftop park.
Mega-braces span up to 75 meters across the building’s façade over the lower two-thirds of the tower. The mega-braces are comprised of three parallel braces, a middle built-up box primary brace and secondary steel braces on either side. One end of the secondary braces is attached to a viscous damper. As the tower sways in wind or seismic events, the system behaves like a giant shock absorber to limit building drift and reduce floor accelerations.
A perimeter steel lateral force-resisting system consisting of mega-braces are utilized to resist wind and seismic forces instead of a traditional concrete or steel core system. Transfer trusses at the third level carry the loads to mega-columns at the corners to create a column-free lobby. The columns are designed to allow slight uplift at their bases in a major earthquake to limit demands on the foundation system. The superstructure is supported by a five-story concrete basement on deep foundations anchored into bedrock.
The building is recognized as the tallest mixed-use building in California. The 181 Fremont Tower is designed to achieve immediate occupancy following a 475-year seismic event. This is accomplished by designing the building to sustain only superficial damage using the innovative lateral system. The design also incorporates enhanced performance criteria for non-structural components such as elevators, stairs, and façade. Arup’s designers have noted that it “would aim to achieve life safety as well as rapid functional recovery by incorporating enhanced seismic design and contingency planning”.
- ASCE Region 9 Outstanding Structural Engineering Project (2018)
- CTBUH Best Tall Building Award of Excellence (2019)
- ASCE SF Section Outstanding Structural Engineering Project (2018)
- DFI Outstanding Project Award (2018)
- CTBUH Structural Engineering Award of Excellence (2019)
- AISC IDEAS2 National Award (2019)