Final Design
After researching over 20 systems and evaluating each against the design criteria, the following final system was selected for a mid-rise building on San Francisco clay requiring immediate occupancy.
It is important to note that all the systems that were discussed in the Research Summary page were not used in the final design. This is because when they are put together, they compete against each other and weaken the structure instead of strengthening it.
THE FINAL SYSTEM
See the table below explaining the final design.
HOW IT WORKS TOGETHER
The ground motion begins, FPS isolators absorb vertical and horizontal forces, viscous dampers control displacement, SMF provides ductile backup, and the piles transfer the remaining loads to stable soil.
In San Francisco clay, the piles bypass the soft soil, and the FPS controls the displacement. The FPS recenters the building, and when it’s paired with viscous dampers and the SMF, immediate occupancy is achievable. None of the elements has height restrictions, so they can easily be applied to a mid-rise building. A similar configuration to this has proven performance at 181 Fermont San Francisco.
The key trade-off of this design is that it has a higher cost, but it is justified by immediate occupancy. It is also complex to make FPS isolators due to precision manufacturing, and the SMF requires RBS detailing. The building would also need space for movement so that it doesn’t hit nearby buildings and cause damage.
3D MODEL
