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RE: Masonry Question

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As stated, the 1/3 stress increase is permitted by IBC and ASCE 7 if allowed by the material standards.  The ACI 530-05 has some good commentary in Commentary Sect. 2.1.2.3 and 2.1.3.4.
 

2.1.2.3 Previous editions of building codes have customarily used a higher allowable stress when

considering wind or earthquake in a structure. This increase has come under attack, and there has been some confusion as to the rationale for permitting the increase. The committee recognizes this situation but has opted to continue to increase allowable stresses in the traditional manner until documentation is available to warrant a change

 

2.1.3.4 Strength requirements - The strength of members and connections is based on working stress

procedures modified by a factor. The nominal capacity is approximated as the allowable stress increased by 1/3 (for the load combinations that include wind or earthquake in accordance with Section 2.1.2.3) and further multiplied by a factor of 2.5.



Regards,
Harold Sprague



From: sdorado(--nospam--at)tbengineeringinc.com
To: seaint(--nospam--at)seaint.org
Subject: RE: Masonry Question
Date: Fri, 14 Mar 2008 08:39:41 -0700

Jason,

                I re-read section 1605.3.2 in the IBC (same as in CBC) and it says the 1/3 increase is allowed when using the alternate load combinations which include wind or seismic, “where permitted by the material chapter or the referenced standards.”  This goes back to my original questions, because I have not been able to find the location in the masonry chapter of the IBC, where it mentions a 1/3 allowable stress increase.  Also, it goes back to the debate I have about the sections in the Building Code Requirements for Masonry Structures (ACI 530-05/ASCE 5-05/ TMS 402-05).  Please let me know what you think.  

 

Salvador Dorado

 

T & B Engineering, Inc.

4344 Latham St., Suite 100

Riverside, CA 92501-1773

P: (951) 684-6200

F: (951) 684-6226

 

From: Jason Christensen [mailto:jason(--nospam--at)wcaeng.com]
Sent: Friday, March 14, 2008 7:37 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Masonry Question

 

Not sure about the CBC, but the IBC allows the 1/3 increase, as allowed by other codes, only when using the Alternate ASD load combos, see IBC 2006 Section 1605.3.2.

 

Jason

 

 

From: Salbador Dorado [mailto:sdorado(--nospam--at)tbengineeringinc.com]
Sent: Thursday, March 13, 2008 5:45 PM
To: seaint(--nospam--at)seaint.org
Subject: Masonry Question

 

Is there an allowable 1/3 stress increase when designing Masonry Shear Walls using the ASD Method?  If so could you please point me to the section of the ACI530/ASCE 5/TMS 602 or the 2007 CBC  where I can find it.  I know that there is a 1/3 stress increase allowed mentioned in section 2.1.2.3 of ACI 530/ASCE 5/ TMS 602 when considering load combination c, d, or e (which contain wind or earthquake loads) of section 2.1.2.1 of the ACI 530/ASCE 5/TMS 602.  However, section 2107A.2 of the CBC requires that section 2.1.2.1 be deleted from the ACI 530/ASCE 5/TMS 602. Does the deletion of section 2.1.2.1 mean that the 1/3 allowable stress increase no longer applies? Or does it mean that the 1/3 increase is still permitted where the ASD Load Combination includes wind or earthquake loading.  Please provide me with some information on this matter.  Thank You.

 

 

Salvador Dorado

 

T & B Engineering, Inc.

4344 Latham St., Suite 100

Riverside, CA 92501-1773

P: (951) 684-6200

F: (951) 684-6226

 



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