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RE: Required wall attachment to a flexible diaphragm.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: RE: Required wall attachment to a flexible diaphragm.
- From: "Niaz A. Nazir" <NAN(--nospam--at)eqe.com>
- Date: Thu, 26 Aug 1999 15:13:42 -0700
Note that the forces in wood members will need to be reduced by a factor of 1.4 for WSD and the 1/3 increase is allowed. The idea was to keep the overstrength factor equal to about 2.0 for all materials, i.e., steel, wood, concrete and masonry etc. Gerard Madden <GerardM(--nospam--at)crjarch.com> on 08/26/99 03:00:09 PM Please respond to seaint(--nospam--at)seaint.org To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org> cc: (bcc: Niaz A. Nazir/EQE) Subject: RE: Required wall attachment to a flexible diaphragm. If you are talking about anchorage to a flexible diaphragm of tilt-up of masonry wall, then ap = 1.5 otherwise 1.0. Rp is 3.0 unless you do not meet the shallow anchorage requirement which is the anchor in the wall must be embedded 8 times its diameter (i.e. 3/4" A.B. must have 6" embedment) otherwise your Rp equals 1.5 and your force doubles. The force (Fp) applies to Anchor bolts, prefabricated HD's & CT's etc.., and all elements of the wall anchorage system (Struts, cross-ties, chords, and subdiaphragms.) Note that Steel elements must be designed to resist 1.4 times the force generated by the Fp equation (In ASD & LRFD steel design). That means anchor bolts, metal straps (steel only, not nails in wood- [that's the way I read it]), and simpson/kc metals/zone 4 hardware must be selected to meet this increased force. But the wood elements, i.e. struts, bolted and nailed connections, and subdiaphragms need only be designed to resist 0.85Fp. Soil type D yields the worst results. Yes . . . the forces get very high . . . don't use shallow anchors!!! Confusing Ain't it. We'll get used to it. (hopefully) Gerard Madden, P.E. Civil Engineer, Associate CRJ Associates, Inc. email: gerardm(--nospam--at)crjarch.com tel: 650.324.0691 fax: 650.324.0927 web: www.crjarch.com > -----Original Message----- > From: From the desk of Joe Otto [SMTP:jmo_engineering(--nospam--at)email.msn.com] > Sent: Thursday, August 26, 1999 2:36 PM > To: Seaint@Seaint. Org > Subject: Required wall attachment to a flexible diaphragm. > > The 1997 UBC Section 1622.214.171.124.1 indicates the values for Rp and Ap > of 3.0 > and 1.5 respectively should be used for elements of the wall anchorage > system. > > What are the components of the wall anchorage system that these values > apply > to? Is it the attachment of the wall to the diaphragm. Or does this > also > include the subdiaphragms and cross-ties? > > if hx = hr ==> Fp = ap*Ca*Ip/Rp*(4Wp) > = 1.5 * (.44*1.2) * 1.0 / 3 * 4 * Wp = 1.06Wp > > This seems high to me. If anyone could take the time to > clarify/confirm > this, it would be appreciated. > > Thanks in advance. > > Joseph M. Otto, PE > Ireland Engineering > Fremont, CA > > > >
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