|A building where any one level is significantly more flexible (less stiff) than those above and below.|
|Used on these elements|
|Tools for this tag|
The tag building:soft_storey is to provide a way to identify buildings in which at least one storey is significantly more flexible or weak in lateral load resistance than the storeys above and below it (70% or greater reduction from one floor to the next according to the current International Building Code (IBC) definition ). This condition can occur in any conventional construction type and is typically associated with buildings in which one or more storey have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability as a matter of earthquake engineering design (according to the Soft story building Wikipedia definition).
The tag needs to be applied carefully. Although citizen responders can be trained to spot soft storey buildings (and this is included in training as part of the U.S. national community preparedness programs such as CERT) only a detailed analysis by structural engineers can definitively identify one. The best way for confirmation is by either obtaining open data released from an official source, like San Francisco Department of Building Inspection (DBI). Alternatively, one can use an assessment worksheet like the one provided by FEMA.
This information will be critical in disaster preparedness and damage assessment. The San Francisco Bay Area alone has about 138,000 soft storey units in varying stages of retrofitting. According to one government report, two-thirds of the uninhabitable housing units in a major quake will likely be soft-storey residential buildings.
How to map
A building can have soft_storey status as
- yes when assessed as having one or more soft story.
- reinforced, if reinforcing measures have been put in place. When known, one can add in the tag 'source:soft_story' the source of the information, such as San Francisco DBI work permit.
- The value no is for buildings that are assessed as having no soft storeys. Don't use no for buildings that have been reinforced.