huangyhg

vibration due to air handling unit/compressor
if an reinforced concrete frame structure, two to three spans, in one direction and the same in the other direction are subjected to vibration due to air-handling unit, causing discomfort to the occupants, what actions do we take? the building is a 3-storey r.c structure. the frames are filled with brick along its periphery. is the structure in any danger?
silly questions - silly answer.
remove the air handling equipment the frame will then not vibrate.
really you need to give a lot more information before any sensible guidance can be given.
describe the building in greater detail. are the slabs spanning in one or two directions? what supports the slabs? what is the horzontal bracing system? what is the building used for? what is the air handling equipment? what is causing the vibration? are there any anti-vibration mountings? how are the occupants discomforted?
how is the unit mounted? have you considered vibration isolating mounts?
i think dbuzz is right on.
all ahu's that i deal with come with vibration isolators to dampen the vibrations (springs, neoprene pads, etc). these are facory supplied devices. i would check on that first.
regards,
lutfi
186,
is this a new installation? has something changed recently? you mention discomfort to the occupants and then ask about structural safety. it sounds serious. perhaps the first action should be to inspect the equipment for possible mechanical failures.
effective isolation of problems like this can sometimes be difficult to achieve.
-mike
this is not a new installation. some of the occupants are already accustomed(conditioned) with the situation. but some occupants say the vibration is stronger than previously.we have asked the mechanical people to inspect the ahu and they said they need to replace some parts of the equipment. i did not notice any cracks on the columns and walls of the affected area.
as dbuzz and lufti mentioned vibration isolators might help. they would attenuate some of the higher frequency vibrations in the equipment that pass from the machinery into the structure. much of the energy however is in the lower frequencies and is much more difficult to control. these vibrations require springs with larger deflections than is usually practical.
i was involved with a problem like this with a rooftop hvac system where vendors and a vibration consultant were called in. some improvements were made but what was really needed was judged to be too expensive by management.
that's not to say your problem can't be corrected however, but you might need to contact an experienced engineer in this field for an onsite visit. it depends on the details. the machinery, structural support, maintenance, etc.
good luck,
-mike

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