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- To: seaint(--nospam--at)seaint.org
- Subject: Sheilding
- From: Brian Kehoe <BEK(--nospam--at)wje.com>
- Date: Thu, 10 Sep 1998 11:07:55 -0500
Gabriel Bohm wrote: >>Your help is requested with the following wind loading situation. I have five identical buildings, spaced 16 feet apart. Building height is 120 feet. Building width is 60 feet - this is the dimension perpendicular to the wind direction. The dimension parallel to the wind direction is 20 feet. The buildings are in perfect alignment, such that the first one effectively shields the other four. Normally, we would design one of the five buildings treated as a self-supporting entity subjected to full wind loading, then simply build five such structures, with or without interconnecting struts. The client, of course, understands the cost implications of this approach. This time, it's different - the client insists that we take advantage of wind load reduction due to shielding, and wants the five buildings to be interconnected and treated as one large structure. ASCE 7-95, paragraph 6.5.4, prohibits shielding, but the client guarantees that the five buildings will always stay together. If so, using shielding makes sense. A call to ASCE confirmed that paragraph 6.5.4 is not gospel. Unfortunately, ASCE 7-95 does not address wind loading for series of buildings. Here are my questions: 1. Is it OK to apply wind loads only on the windward wall of building 1 and leeward wall of building 5? 2. Is it reasonable to assume that, as the wind goes around the buildings, vacuum will develop in the spaces between the buildings, which in turn will generate suction on all interior wall surfaces? 3. If my above assumptions are incorrect, what would be the correct approach for applying wind loads? <<< If your client wants to treat these buildings as a group, then you should change the distance between buildings to something smaller than 16 feet. I agree with an earlier post that wind tunnel tests should be conducted to verify the amount of shielding benefit from these buildings at that distance. The end buildings have an aspect ratio of 6 to 1 with only 20 feet to resist the lateral forces. Depending on the lateral system chosen, the seismic design of the middle buildings may not require a large increase to accomodate the wind design. If your client still wants to treat these buildings as a group ask this question: If a fire, earthquake or other natural disaster damages one of the buildings to the point where it needs to be replaced, is your client going to tear down all of the buildings? If not, then you still need to have the other buildings designed without considering the sheilding.
- Re: Sheilding
- From: Bill Lynch
- Re: Sheilding
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