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RE: UBC 1633.2.5 clarification

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If you are designing a positive connection for a beam, you can divide E by 1.4 in an ASD load combinations that show E divided by 1.4.  If you are designing a tie at a re-entrant corner I think 1633.2.5 provides a lower limit on the force to tie the strength level force to tie portions of the building together but it does not tell you that it needs to be checked for strength like 1633.2.6.  I think you could check 1633.2.5 with ASD but 1633.2.6 still reads to be checked for strength.

 -----Original Message-----
From: Pat Clark [mailto:bcinc(--nospam--at)nanosecond.com]
Sent: Wednesday, October 30, 2002 8:55 AM
To: seaint(--nospam--at)seaint.org
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?
 
Pat
----- Original Message -----
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-----
From: Pat Clark [mailto:bcinc(--nospam--at)nanosecond.com]
Sent: Tuesday, October 29, 2002 1:37 PM
To: seaint(--nospam--at)seaint.org
Subject: 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.