Seismic Restraints

Seismic Rod Bracing Clamps

SRBC Series

The SRBC Series are seismic rod bracing clamps used as additional support for bracing threaded rods used to suspend piping, ducts, conduit and other HVAC equipment. 

Seismic forces act in all directions. Threaded rods are sized purely for gravity loads, making it necessary to add additional rod bracing to prevent buckling of the rods. Uplift forces can easily exceed the dead load on the rod – resulting in compressive forces. If not braced, the rod can buckle and fail. With the addition of the VMC SRBC Series bracing clamp, angle steel bracing can be quickly and easily added to the rod.

When vibration hangers are utilized, VMC recommends attaching the hanger directly to the overhead structure and adding an uplift washer under the box to prevent the spring from becoming unloaded.

Seismic Cabling

SCR Series
Up to 4200lb. Capability

Seismic cable restraints are an excellent way to restrain suspended equipment, piping, and ductwork during an earthquake.  Cables are designed for use in conjunction with externally mounted vibration isolator systems and can withstand up to 1g of force.

Piping, ductwork, and other equipment are typically suspended on vibration isolation hangers within mechanical equipment rooms.  However, this equipment must also positively attach to the structure of the building in case of an earthquake.  Floor-mounted equipment uses a seismically rated vibration isolator or separate snubber.  No such device exists for suspended equipment because it can have any number of possible elevations.  

While isolated piping or ductwork must be seismically restrained to the building structure, it must not compromise the vibration isolation - also known as “short-circuiting”. A “run” of pipe or ductwork must be restrained both longitudinally (in the direction of its run) and transversely (perpendicular to its run) to ensure that it moves with the building and remains attached to the building during an earthquake. VMC seismic cable restraints ensure positive attachment to the ductwork, and when installed slightly slack, do not compromise the vibration isolation by short-circuiting the isolation hanger.

Many different installation configurations are possible and may affect the performance of the restraints. VMC seismic cable restraints are positioned at a 45o angle from the point of support. The diameter of the cable is based on the weight of the equipment and specified seismic force. The SCR Series is made from 7 x 19 air- craft cable and sizes are available in 1/8”, 1/4” and 3/8” diameters.

The VMC seismic cable restraints are packaged in kits to minimize labor cost for the contractor. Each pre- packaged kit contains all of the necessary hardware for proper installation and positive attachment to the building structure. Each piece of equipment requires a mini- mum of four cables, or two SCR kits. VMC SCR Series is factory swaged on one end to minimize installation time. The VMC SCR Series strictly complies with national building code requirements and building codes such as IBC2000, IBC2003 and NFPA5000.

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Single Arm Braces

SAB Series
Up to 2400lb. Capability

The SAB series offers an ideal solution for restraining suspended equipment, piping, ductwork and electrical cable trays during an earthquake.  The SAB series is designed for use with equipment that does not have external vibration isolation systems.  With the SAB series, non-isolated ductwork, piping, and conduits that are rigidly supported can still be seismically restrained.  

The electrical system in a building is a very important part of the HVAC system.  Should the power be interrupted due to inadequately restrained electrical systems, the HVAC system will be rendered inoperable.  While designers typically take great strides to ensure that the mechanical equipment, pipes and ductwork are properly restrained, the electrical system is often overlooked.  Any electrical conduit or cable trays used to supply power to the HVAC or to emergency backup systems must also be properly restrained. 

VMC single arm braces consist of two brackets that allow the brace a full range of motion in all directions.  This provides easy installation and saves on contractor labor costs.  The bracing material - typically channel strut or angle steel - is contractor supplied and cut to size in the field.

The brackets are available in two sizes and incorporate properly sized and spaced anchor bolt holes.  The SAB-1 is designed for attachment to the pipe hanger and anchoring into steel.  The SAB-2 incorporates two anchor bolt holes for attachment to concrete.  The SAB Series requires only one brace per longitudinal location.  The braces are installed at 45 degrees from the horizontal place of the equipment, and perpendicular to each other at either end of the equipment.  The VMC SAB Series strictly complies with national building code requirements and building codes such as IBC 2000, IBC 2003, and NFPA 5000.

Seismic Roof Curbs

Model: P Series & R Series

VMC's "P" series curbs and "R" series rails are high quality, fully adjustable support systems specifically designed for rooftop unit vibration isolation  and seismic/wind restraint.  Each custom built unit incorporates both the roof curb and spring isolation into one complete structure.  VMC engineers design each curb and rail to custom fit any rooftop mechanical equipment.

These fully flashable rooftop support systems also save the contractor unnecessary labor costs.  The curb and and rooftop unit can be fully installed and adjusted before the roof is sealed, eliminating the possibility of any damage to a finished roof.