Earthquake engineering for the design of base isolation has emerged as one of the strongest tools for control of structural vibration. When the potentially dangerous earthquakes occur, it is the seismic mountings for the vibration isolation that come into play and protect the building or non-building structure from damage. The importance of the seismic isolation devices and seismic mounts is not understood by the people till they see the devastation with their own eyes. However, the awareness about the subject and the media coverage of natural disasters has made the people cautious about seismic isolators.
Seismic base isolator: The methodology used in the past was to add braced frames and shear walls to strengthen the structure from the impact of the earthquake. This action was increasing the rigidity of the structure making it vulnerable to the seismic impact. The
seismic base isolator is a workable approach that isolates the structure from the ground below, reducing the propagation of seismic shock into the structure. Besides reducing the structural damage, the seismic isolation results in the protection of the other equipment like computers, precision instruments, medical devices, and communication hardware from damage.
Seismic isolation for HVACs: The seismic restraint guidelines must be followed for the installation of suspended piping, ductwork, conduits and cable trays. While the seismic HVAC isolation separation mounts are to be used for the heavier equipment like air conditioners, chillers, and AHUs, the adequate use of hanging spring isolators is recommended for the piping and ducting. It is also recommended to use transverse and longitudinal braces for the suspended piping and ducts. The seismic isolator manufacturer is likely to guide you for the seismic mounting hardware.
Seismic mounts: The ordinary vibration mounts provide vibration isolation. However, this feature is combined with a multi-directional flexible restraint to prevent the movement of equipment under the seismic forces in a seismic isolator. Thus, the movement of the equipment relative to the supporting structure is restricted. However, there is a limit to the restraint capacity along any major axis and is capped at 12 mm. Similarly, the seismic brackets for packaged units are standardized steel brackets with rubber grommet washers to minimize the impact of the seismic shock forces at anchor locations.
Isolation hangers: The hanger springs are designed to reduce the vibration and noise
generated by the hanging equipment. The isolation hanger consists of a stamped bracket with a spring, cap and elastomer element. The springs have lateral spring stiffness almost equal to the vertical stiffness. The hanger spring also allows for a support rod misalignment through a 30-degree arc. The major applications for the isolation hangers are the isolation hanger duct and isolation hanger acoustic ceiling.
Among the seismic isolator manufacturers, Andre HVAC International Inc. has taken the lead in the product variety and availability of the seismic isolation units. Whether it is the seismic bracket or the HVAC vibration hangers you are likely to find the complete seismic solution at AHI.