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[SEAOC] RE: [SEAOC] Single jolts like an EQ, but not EQ!!!!![Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc <seaoc(--nospam--at)power.net>
- Subject: [SEAOC] RE: [SEAOC] Single jolts like an EQ, but not EQ!!!!!
- From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
- Date: Wed, 06 Nov 96 15:55:00 PST
- Encoding: 72 TEXT
Obtain some more information. I would tend to discount any residual "locked-up stresses". They would have manifested into perceptible vibrations some time ago. Check the mechanical equipment. If there are isolators, are they still in proper working order? Can the timing of the perceived vibrations be linked to any of the mechanical equipment, like the compressors for the HVAC equipment? Have the HVAC compressors switched on in various sequences in an effort to simulate the perceived vibrations. What were the environmental conditions immediately prior to and during the vibrations. Did the perceived vibrations occur at night, sunny conditions, etc.? Elements heated by solar gain during the day will shrink again when the sun goes down. This cycling can produce stresses in the internal structure of the building. Check to see if any heavy equipment is operating close to the building. A large refuse bin dropped a few inches can send a shock wave through a building. Try to determine a pattern of the vibrations, and a pattern to potential vibration sources, and see if you can find a match. Good luck. Harold Sprague, spragueho(--nospam--at)bv.com ---------- From: seaoc To: seaoc Cc: seaoc; asl-cse Subject: [SEAOC] Single jolts like an EQ, but not EQ!!!!! Date: Wednesday, November 06, 1996 3:32PM I am talking about a 5-story office building in the S.F. Valley, designed and constructed in the early/mid sixties. Steel frames in both directions (with welded cover plates), grade beams at the base, pile foundation. Floor framing is lt.wt. concrete fill over plywood on wood joists spanning between steel beams. A few tenants (at one side of the building) are complaining about random "jolts" that started about a year ago and are occuring increasingly. Naturally the owner would like to find out what is going on (and so do I !) By the way, the one and only side of the building where the complaints are coming from has continuous brick spandrels which are supported top, btm. & mid-height at every column (about 21 ft o/c). One of my guesses is that there might be some "locked-up stresses" which are being "released". (Spandrel connections and/or welded connections). There appear to be no visual deformations and/or cracks. The building was "inspected" after the EQ by a structural engineer, but no beam/col or spandrel/col connections were exposed or inspected. I thank your for the upcoming comments and suggestions. Antonio S. Luisoni Consulting S. E. ... ...
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