Seismic Bracing Company

Earthquake Brace

What's a BRB & why use them?

What’s a BRB?

Basically you take a solid steel core, typically rectangular in shape, then wrap it in special material, then place it through a steel tube and then fill the space between the core and the tube with grout.  The special material prevents the steel core from bonding with the grout so the grout and tube will not take any load and only the steel core does.  The grout and steel tube are only needed when the steel core is in compression and tries to buckle.  The grout confines buckling of the steel core on a local level and the larger more stable steel tube surrounding the grout prevents the entire BRB from buckling.  In tension the grout and steel tube do nothing and just go along for the ride.

 
BRB Config.PNG
 

Why they are so cost effective?

The cost effectiveness of BRBs comes from two major factors.  The first factor is their ductility/durability, which allows the engineers to reduce seismic loads more than ordinary braced frames.  The second factor is the orders of magnitude of less force BRBs can possibly deliver to the structure than ordinary braces.  Ordinary braces have a much lower compressive strength than their tension strength because they buckle in compression.  With BRBs, we just need to provide enough cross sectional area for the steel core to handle the seismic force.  With ordinary braces you have to size them so they won’t buckle and then you have all this extra material that can deliver orders of magnitude more force to the structure when in tension.  In both BRB and ordinary braced frames, the entire braced frame structure must be capable of sustaining the maximum force the brace can deliver.  Thus, for BRBs, the braced frame connections, columns, beams and foundation sizes can be reduced by a major amount.

 
 
 

Occupancy (Insurance):

BRBs are capable of sustaining deformation far greater than they will experience during big earthquake and their durability can sustain several big earthquakes.  Thus, the chances of occupying and utilizing a BRB braced building after an earthquake is more likely.  Ordinary braces will most likely buckle during a big earthquake and possibly fracture making it less likely to be able to occupy and use an ordinary braced building after an earthquake.  Therefore, since BRBs are more cost effective it’s like getting paid to insure your structure.