Insulating concrete form saferoom from FEMA 320.
Two important areas to consider when designing safe rooms with precast concrete are the connections between the panels/sections and the debris impact-resistance of some sections. Connectors must be able to withstand large loads generated by extreme winds.
For debris impact-resistance, some systems must be further protected. For example, when standard single- and double-tee precast sections are used for roof systems, a “topping” layer of reinforced concrete is typically required to meet the debris impact-resistance criteria.Insulating concrete forms
To help homebuilders and homeowners build economical safe rooms for both new and existing homes, the Portland Cement Association, American Polysteel, and Lite-Form International worked together to develop safe room plans specifically for insulating concrete forms (ICFs).
Made of foam insulation or other insulating material, the forms typically have one of two basic configurations: pre-formed interlocking blocks into which the concrete is placed, or individual panels with plastic connectors that form cavities into which the concrete is placed.
Thanks to the efforts of these industry partners, FEMA 320 includes using ICFs. The sections provided in the FEMA 320 plans have all been tested and shown to resist a 15-pound, 2x4 projectile traveling at 100 mph. Note there are some ICF products called screen grid forms, shaped similar to waffle grid forms. These ICF products create a discontinuous concrete infill (voids), and should not be used in safe room construction.
With a constantly evolving industry, new technologies and adaptations are on the horizon. In addition to modified mix designs, the market is already seeing advances using Kevlar in conjunction with concrete to resist debris impact. As the industry advances, new materials and construction methods will be developed to enhance the durability, feasibility, and robustness of FEMA safe rooms.
The 2008 release of the FEMA 320 and 361 safe room documents, along with the ICC-500 Storm Shelter Standard, was a significant milestone in standardizing criteria for structures built to provide protection from tornadoes and hurricanes.
With the incorporation of the ICC-500 Storm Shelter Standard into the 2009 IBC and IRC, most of the FEMA safe room criteria that have been used since the 1990s have now been codified. It is now the challenge of designers, emergency managers, owners/operators, and industry groups and participants to strive toward producing quality safe rooms that meet the new criteria.
CLICK HERE FOR THE WEB EXTRA ARTICLE: FEMA Updates Safe Room Publications:Changes for Concrete Safe Rooms
John Ingargiola is a senior engineer with FEMA. Tom Reynolds and Scott Tezak are senior engineers with URS, a provider of engineering, construction, and technical services based in San Francisco.
For more on FEMA safe rooms, visit www.fema.gov/plan/prevent/saferoom, contact the FEMA Safe Room Help Line at firstname.lastname@example.org, or telephone 866-222-3580.