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Re: IBC 2009/ASCE 7-05 Allowable Stress Increase

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Section says you can use the 1.2 increase if you are using the Basic 
 Combinations for Allowable Stress Design with Overstrength Factor, equations 
 5,6, & 8, and if your supporting member is wood then you are also allowed 
to combine it (see exception below) with the load duration factor increase 
of 1.6 per AF&PA NDS.

" Load Combinations with Overstrength Factor


Basic Combinations for Allowable Stress Design with Overstrength Factor 
(see Sections 2.4.1 and 2.2 for notation).

5. (1.0 + 0.14SDS)D + H + F + 0.7ΩoQE
6. (1.0 + 0.105SDS)D + H + F + 0.525ΩoQE + 0.75L +0.75(Lr or S or R)
8. (0.6 – 0.14SDS)D + 0.7ΩoQE + H Allowable Stress Increase for Load Combinations with Overstrength

Where allowable stress design methodologies are used with the seismic load 
 effect defined in Section

12.4.3 applied in load combinations 5, 6, or 8 of Section 2.4.1, allowable 
 stresses are permitted to be determined using an allowable stress increase 
 of 1.2. This increase shall not be combined with increases in allowable 
stresses or load combination reductions otherwise permitted by this standard 
 or the material reference document except for increases due to adjustment 
 factors in accordance with AF&PA NDS."   If I recall correctly, the 
increase used to be 1.7 in addition to the 1.33 for wood design about two 
or three code cycles ago.

Oshin Tosounian, S.E.

 From: Michel Blangy <mblangy(--nospam--at)>
To: seaint-seaosc(--nospam--at)
Sent: Friday, August 1, 2014 9:03 AM
Subject: RE: [SEAINT-SEAOSC] IBC 2009/ASCE 7-05 Allowable Stress Increase


My question is whether I can use 1.2 with eqtn.


-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On
Behalf Of Himanshu Goyal Sent: Friday, August 01, 2014 8:44 AM
To: seaint-seaosc(--nospam--at)
Subject: Re: [SEAINT-SEAOSC] IBC 2009/ASCE 7-05 Allowable Stress Increase

Yes per the ASCE7-05, the allowable stress increase of 1.2 can be used for
load combinations with over strength factor (5,6 and 8) as listed in 

Himanshu Goyal

On Thu, Jul 31, 2014 at 5:32 PM, Michel Blangy <mblangy(--nospam--at)>

Truncated 1125 characters in the previous message to save energy.

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