FEMA 453 Design Guidance for Shelters and Safe Rooms

Figure 2-20
Steel jacket retrofit detail
2.5.2.4 Structural Upgrades. Conventionally designed columns
may be vulnerable to the effects of explosives, particularly when
placed in contact with their surface. Stand-off elements, in the
form of partitions and enclosures, may be designed to guarantee
a minimum stand-off distance; however, this alone may not be
sufficient. Additional resistance may be provided to reinforced
concrete structures by means of a steel jacket or a carbon fiber
wrap that effectively confines the concrete core, thereby increasing
the confined strength and shear capacity of the column,
and holds the rubble together to permit it to continue carrying
the axial loads (see Figure 2-20). The capacity of steel flanged
columns may be increased with a reinforced concrete encasement
that adds mass to the steel section and protects the relatively thin
flange sections. The details for these retrofits must be designed to
resist the specific weight of explosives and stand-off distance.
1" Clear space
around columns
filled with 5,000 psi
non-shrink grout
Concrete
Sand blast concrete
surfaces prior to
jacketing
Chip corners 1"
and grind
smooth
3/8" Steel jacket
1" Radius
bent plate
2- Structural deSign criteria