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Re: UBC 1633.2.5 clarification

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According to the UBC Errata they have changed the last sentence of 1633.2.5 from "0.5CaI" to "0.3CaI" but interestingly this has not been picked up in the new 2001 CBC.  Anybody know if the errata is correct??

Thomas Hunt, S.E.
ABS Consulting

"Pat Clark" <bcinc(--nospam--at)>

10/30/2002 09:55 AM
Please respond to seaint

        To:        <seaint(--nospam--at)>
        Subject:        Re: UBC 1633.2.5 clarification

I'm pretty familiar with 1633.2.6, and understand those provisions.  I'm questioning 1633.2.5, where they want an increase to 0.5 Ca*I*W, which is well above my system seismic load.  Can this load be reduced by 1.4 for ASD? Does this increase affect both the connectors and the element?
----- Original Message -----
From: Haan Scott M DPW CIVIL ENGR(n)
To: seaint(--nospam--at)
Sent: Wednesday, October 30, 2002 9:01 AM
Subject: RE: UBC 1633.2.5 clarification

UBC 1633.2.6 Talks about designing collectors = drag struts.  It says use the regular diaphragm formula 33-1 for wood and that you can multiply the collector capacity by 1.7 to determine it's strength without a 1.33 ASD increase.  Dividing by 1.4 is in UBC 1612 ASD load combinations which are not mentioned in 1633.2.6 so you can't divide by 1.4 if you are checking collectors but you multiply the capacity by 1.7 to determine strength so it comes out in the wash.  1.33*1.4=1.862>1.7, so there is a slight hit for collectors in 1633.2.6.
-----Original Message-----
Pat Clark [mailto:bcinc(--nospam--at)]
Tuesday, October 29, 2002 1:37 PM
UBC 1633.2.5 clarification

1997 UBC notes the following:

1633.2.5 Ties and continuity. All parts of a structure shall be interconnected and the connections shall be capable of transmitting the seismic force induced by the parts being connected. As a minimum, any smaller portion of the building shall be tied to the remainder of the building with elements having at least a strength to resist 0.5 CaI times the weight of the smaller portion.

A positive connection for resisting a horizontal force acting parallel to the member shall be provided for each beam, girder or truss.This force shall not be less than 0.5 CaI times the dead plus live load.

For a wood framed structure (R=5.5), with a drag strut or drag truss, would this minimum force include the drag truss or strut capacity, the connectors/fasteners, or both.  Can it be divided by 1.4 to get back to ASD level forces?


Thanks in advance,

Pat Clark, P.E.