1/3 increase for seismic/wind for masonry?

[seattlemike]

There has been some talk that the 1/3 increase for masonry is going away in the IBC 2006. But it's still in the IBC 2003, right? 2.1.2.3 of the ACI 530-02/ASCE 5-02 seems to allow the 1/3 stress increase, which can be used with the ALTERNATIVE basic load combinations of the IBC 2003.

What do you think?

 

[haynewp]

Look in IBC chapter 21 and make sure that section of ACI 530 is permitted.

 

[Bagman2524]

That's my understanding as well.

 

[seattlemike]

haynewp,

your response is bit vague, not too helpful in it's current form. perhaps you could be more specific if there a particular passage you are aware of?

thanks,
mike

 

[haynewp]

I am away from the office today so I don't have the IBC with me right now, but I know it removes parts of other standards as being applicable (such as ACI 530). I don't know specifically if it does this with the 1/3 increase as you stated is in 530, because I don't have chapter 21 memorized. But I would check CH 21 to make sure there is not something like "ACI 530 applies with exception of sections 2.1.2.....etc." before I assume the 1/3 increase is permitted by IBC 2003 for masonry.

 

[Ron]

The 1/3 overstress allowance has been removed from almost every other structural consideration as well....why not masonry now!

 

[DaveAtkins]

In the current IBC, the 1/3 increase IS allowed for the alternative load combinations, but that is because the alternative load combinations multiply wind load by 1.3 (which is approximately a 1/3 increase). I don't use the alternative load combinations, and I don't use the 1/3 increase for masonry (or steel).

DaveAtkins

 

[haynewp]

I haven't used IBC 2003 as much as 2000. Is the seismic force the same between the standard and alternate load combinations or is there some other hidden multiplier as well? I never use the 1/3 increase either anymore, even when I am allowed.



Mendacity is a system that we live in. Liquor is one way out and death's the other.
-Tennessee Williams

 

[Bagman2524]

2101.2.3 Prestressed Masonry shall be designed in accordance with Chapters 1 and 4 of ACI-530.
2101.2.4 Masonry designed by the empirical designed method shall comply with the provisions of 2106 and 2109 or Chapter 5 of ACI-530.
2101.1,2 Masonry shall comply with 2106,07 & 08
2106.1 Masonry structures shall comply with 1.13.2.2 of ACI-530.
2107.1 Masonry WSD shall comply with Chapters 1&2 of ACI-530.
2108.1 Design of Masonry per strength design shall comply with chapters 1 & 3 of ACI-530.
There are some exceptions mixed in there.