Should both internal and external vibration isolation be used in a single application? ANSWER: It is possible that the internal springs could resonate with the external springs. This could cause damage to the systems. If the application is near a very vibration sensitive area, the internal isolators should remain locked down; as they are when …
The mechanical equipment is all located on grade outside the building or in a central plant. Do I still need earthquake restraints? ANSWER: The location of the equipment does not change the requirements for seismic bracing. However, the design forces that must be resisted will change based upon the location of the equipment in or …
I am thinking of replacing an aging air conditioning system. Should I add seismic restraint devices with the installation? ANSWER: In the event of an earthquake of a magnitude large enough to cause your air conditioning equipment and piping to break loose, you could lose the use of the building and have the risk of …
Is it possible that a building could be uninhabitable after an earthquake, even with no structural damage? ANSWER: The heating and air conditioning system equipment are considered to be non-structural components of the building. If the building has little or no structural damage but the water piping or air conditioning systems have torn loose or …
The seismic design forces have greatly increased with the advent of the current code in my area. In addition, there is a lot more information that I need to have to determine what force is appropriate. Why is this? ANSWER: During the 1989 and 1994 earthquakes that occurred in California, considerable information was gathered that …
What is “special inspection” for anchor bolts? ANSWER: The actual installation of the bolt into the concrete is a critical part of the restraint system. If the bolt is not embedded deeply enough or properly set into the concrete, it could fail in an earthquake. Special Inspection requires an independent authority to watch the installation …
Why do I sometimes need to add oversized mounting plates to restraints attached to concrete ANSWER: The seismic restraint manufacturer has probably designed the steel restraint so that it is stronger than the material it is anchored to. A good example is when there is a requirement to anchor to a thin layer of lightweight …
Why do I need to provide restraints on equipment that is hung 12″ or less from the ceiling? ANSWER: Although from a philosophic viewpoint it would seem that the rules stated in the questions above should apply to equipment, this is not the case. Equipment behaves more erratically than piping or ductwork during a seismic …
Why do I not have to restrain piping or ductwork that is hung 12″ or less from the ceiling? ANSWER: Items that are hanging on supports react to earthquakes act as though supported on a pendulum. If the pendulum is 12″ or less, its natural frequency is outside the range generated by earthquakes. Because of …
If I follow the current code standards, will my building weather an earthquake without any problems? ANSWER: The codes are based on the maximum “likely” earthquake that has a 2% chance of occurrence in the next 50 years. This means there is a very small chance that an earthquake can occur that is larger than …
