A soft-story building is a multi-story structure built with a first floor that is open in nature, much less rigid (soft) than the floors above. There are many examples of buildings with soft-story conditions including multi-family apartment buildings with tuck-under parking or subterranean parking.
Soft-story apartment buildings are prevalent in California known to be the most earthquake-prone territory. Soft-story / apartment buildings are at risk of earthquake damage however; seismic retrofits will help mitigate the destruction for vulnerable structures.
The main feature soft-story buildings are easily recognized by is also the main reason for structures to collapse or fail in an earthquake. This popular design feature is known as, tuck-under parking (parking that is below raised parts of the structure), very common for apartment buildings. Cities are constantly updating CA building codes in order to adhere to Life Safety standards. A helpful guide for soft-story building policies is the Soft-Story Model Ordinance and Handbook, https://abag.ca.gov/sites/default/files/soft_story_model_ordinance_1.pdf
What happens to a building during an earthquake? Most earthquake-induced building damage is a result of ground shaking. When the ground shakes at a building site, the building’s foundation moves with the Earthquake causing the structure built above the ground to move even more than the ground based on the height and weight of the structure. Some building types are better able to resist these ground motions better than others. Soft-story apartment buildings in Los Angeles and the San Fernando Valley built prior to 1980 are at risk of collapsing during an earthquake. The first story is far too weak to support the entire structure above during an earthquake. Therefore, it is imperative to perform seismic retrofits on all the vulnerable soft-story buildings.
The Soft-Story Program Handbook is a guide to help city and county government interested in addressing susceptible soft-story structures, it is outlined in the following sections:
- Fragile Apartment Buildings: The Soft-Story Problem
- Preparing a Retrofit Program
- Developing Retrofit Policy and Program Elements
- Implementing a Retrofit Program
Review the handbook here, https://abag.ca.gov/sites/default/files/soft_story_report_web_version_v2_1.pdf
Saunders Construction is the premier seismic retrofit solution company in California and has been performing soft-story seismic retrofits since 1980. Saunders Construction now services five states, California, Washington, Oregon, Nevada, and Utah, https://saundersseismic.com/contact/