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RE: 2nd try - Subject of Code Clarification - Non-Building Structures

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Shirish,

You haven't had much of a response, but I'll give it a shot.  I do not have the California code, but I do have the 1994 UBC.

Questions 1 & 2:  Your scenario refers to a nonstructural component, but your question pertains to a nonbuilding structure.  There is a distinct difference.  What is it that this problem relates to?

Question 3:  AISC Table J3.3 applies to fasteners in bearing-type connections and does not apply to rod braces of nonbuilding structures.  In general you are allowed to use the 1/3 stress increase for ASD, but do not forget to factor up the applied loads as required by the UBC provisions for tension only concentric braced frames.  See UBC 2211.8 and specifically UBC 2211.8.2.3.

I understand and empathize with your confusion.  It is for this reason that the NEHRP / BSSC created the "Nonbuilding Structures" technical subcommittee which I have the privilege to chair.  We worked very closely with the "Nonstructural Components ... " technical subcommittee during the last cycle in an attempt to provide more clarity for the practitioner.  

The 1997 NEHRP should be available soon, and I would appreciate your comments.

Harold Sprague, PE, Office Manager
Krawinkler, Luth & Assoc.
4412 W. Eisenhower Blvd.
Loveland, CO 80537
Voice: 970 667-2426
Fax: 970 667-2493
Email: hsprague(--nospam--at)klaalov.com


-----Original Message-----
From:	ShirishM(--nospam--at)aol.com [SMTP:ShirishM(--nospam--at)aol.com]
Sent:	Thursday, February 19, 1998 2:02 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	2nd try - Subject of Code Clarification - Non-Building Structures

The first time this message was sent on 02/12/98. Having had no response, this
is my second request. No offence as every-one is busy. Anyone with any
comments - as to what is reasonably correct the following condition?

Per 1995 California Building Code (1994 UBC), Chapter 16A, section 1630A-1632A
for Non-Building Structures, Table 16A-O as a reference.

I need clarity and or interpretation to the following scenario:
Wp = DL + contents(LL)
Horizontal seismic force = Fp = 0.3*Wp
Vertical seismic force = 1/3*Fp  per footnote 12
When calculating OTM and RM for a non-building structure:

1) The vertical component of seismic force: isn't this supposed to be applied
to anchorage analysis only? and not for the entire non-building structure.
 
If one uses 1/3*Fp acting vertically upwards for overturning analysis together
with Fp for OTM, than what is correct for question #2?

2) When calculating resisting moments, is one supposed to use Wp , or 0.85*DL
plus LL or should it be 0.85*Wp  to resist overturning moment? (Section
1631A.1)

Last but not least,

3) For rod-bracing in metal building strutures or non-building structures,
rods are used as tension braces only. The tension force has two components
when connected to a primary frame - one in direction of frame and the other
perpendicular. If one uses AISC, Part 5, Table J3.3 for allowable tension
stress Ft, at the connection of rod to primary frame. Is one allowed to
increase the tension stress due to wind or seismic (*1.33) or does footnote #1
of Table 16A-O over-rule this increase?

I would like your opinions as to the interpretations and what are the general
acceptable practices for the three questions?

Shirish V. Mistry. S.E.


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