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[SEAOC] Seismic retrofit criteria[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaoc(--nospam--at)seaoc.org'" <seaoc(--nospam--at)seaoc.org>
- Subject: [SEAOC] Seismic retrofit criteria
- From: "Estes, Kent R." <kent_estes(--nospam--at)wdi.disney.com>
- Date: Thu, 19 Dec 1996 08:51:20 -0800
It has been a little quiet, so here is a general question that might generate some interest. There has been some discussion about seismic analysis of existing buildings relative to FEMA documents. My question is, what are the latest criteria when dealing with modifications to an existing building that triggers a seismic upgrade? Maybe I'm missing something, but the FEMA documents and others don't seem to give specific criteria which, if violated, initiate a seismic upgrade. I'm thinking more of specific criteria that I have run into in the past such as: altering the stiffness of a shear wall or adding additional mass to a building more than a certain percentage, altering the building more than a certain percentage of the total cost of the building, etc. To get even more specific, does shifting an existing brace to an adjacent bay necessitate a seismic upgrade of the whole building? If the same brace is simply relocated on the same column line for an interior remodel, I would think not. If the use of a building is altered such that new and more mechanical units are required, does this increase in mass (and possibly new mechanical floor area inside a building) require a upgrade to the latest code? Does a change in occupancy trigger a seismic upgrade? What is the latest thinking? More often than not, I have seen criteria like this in internal memos that are enforced by a given municipality, such as the City of L.A. or OSA. Are there intermediate upgrades that are acceptable, such as 75% of the current base shear? There may be two categories of responses to this issue: those based on one's experience and judgment, and those based on specific criteria from a given governmental agency. Both of which may be valid in their own way and would be interesting to discuss. Specific criteria from building officials would be interesting also. ...
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