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RE: Table 16-O - Horizontal Force Factors, ap and Rp[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Table 16-O - Horizontal Force Factors, ap and Rp
- From: Harold Sprague <harold.sprague(--nospam--at)neenan.com>
- Date: Mon, 30 Aug 1999 09:21:54 -0600
I would suggest that anyone interested in this topic should review chapter 6 of the 1997 NEHRP Provisions and the Commentary. Rick Drake is being a bit modest by not mentioning that he and Bob Bachman did a ton of work on this topic. It is well presented in the NEHRP documents. Regards, Harold Sprague The Neenan Company -----Original Message----- From: Rick.Drake(--nospam--at)fluordaniel.com [mailto:Rick.Drake(--nospam--at)fluordaniel.com] Sent: Monday, August 30, 1999 8:01 AM To: From the desk of Joe Otto Cc: Seaint@Seaint. Org Subject: Re: Table 16-O - Horizontal Force Factors, ap and Rp The a-sub-p factor in the 1997 UBC represents the dynamic amplification factor, relating the dynamic properties of the component to that of the structure. Knowing the fundamental period of both the component and the structure, this value can be exactly determined using basic dynamic principles. However, since this value is not practical, a-sub-p has been assigned a value based on whether the component is either "rigid" or "Flexible", a-sub-p of 1.0 and 2,5 respectively. This is analogous to the 1994 UBC method of multiplying C-sub-p times 2 for flexible items. If your equipment is rigid, and not on vibration isolators (see footnote 14), a-sub-p of 1.0 is appropriate. If not, a-sub-p of 2.5 is appropriate. Rick Drake, SE Fluor Daniel, Aliso Viejo, CA ******************************************* From: "From the desk of Joe Otto" <jmo_engineering(--nospam--at)email.msn.com> AT fdinet on 08/26/99 02:01 PM EDT To: "Seaint@Seaint. Org" <seaint(--nospam--at)seaint.org> AT fdinet@ccMTA-fdlncta10 cc: (bcc: Rick Drake/AV/FD/FluorCorp) Subject: Table 16-O - Horizontal Force Factors, ap and Rp On one of our jobs, we're installing some air conditioning package units on top of a typical panelized roof. We used a value of 1.0 for ap as required by 3.B in Table 16-O (page 2-33). We received a plan check comment indicating that the value of ap should be 2.5 because the attachment of the unit is below its center of mass as is required by 3C. If I use the 2.5 value, I get a value which is greater than that required for emergency power systems (3.D) and containers with flammable hazardous materials (3.E). Both parts of the code appear to apply? Can anyone clarify when 1.0 or 2.5 are truly intended to be used. Thanks in advance. Joseph M. Otto, PE Ireland Engineering Fremont, CA
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