AB spacing at exterior shear wall

[AELLC]

In single family residential construction, is there an IBC code requirement that anchor bolts be spaced at 48" max? Or is this only required in commercial (including multifamily residential)?

 

[woodman88]

Which IBC?
The 2003 IBC section 1805.6 states to use chapter 23. Chapter 23 states you can engineer the spacing or you can go the the conventional section 2308.3.3 that states 48" o.c. maximum.
The IBC 2009 conventional section 2308.6 states 72" o.c. maximum.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[AELLC]

Garth,

We had a shearwall schedule that cited the 48" max and we were wondering where the 48" oc was coming from.

It looks like the 48" was a conservative misinterpretation of the Code because our AB spacings are automatically calculated now.

Thanks

 

[AELLC]

postscript - I asked the same question on another engineering forum and they claim the 48" max applies to ALL wood structures more than 2 stories, irregardless of whether the wall is a shearwall or not.

 

[msquared48]

I would ask them "Show me the meat!"

IBC,IRC, BOCA, what?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[AELLC]

Mike,

It was shown in the 2006 IBC Sect. 2308.3.3

Now that I have re-read it again, it states the sill plate anchorage of braced wall lines (shear walls, whether exterior or interior) of structures more than 2 stories shall be at 48" oc max.

That is logical anyway because you wouldn't expect to have very light shear forces (<150 plf)in a 3+ story structure

 

[woodman88]

AELLC, You are correct, the 48" o.c. is for over two stories in the 2003 IBC also. Section 2308.6 state the maximum spacing as 72" for up to two stories.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[jhoulette]

AELLC
When you said
"the AB spacings are automatically calculated"
What did you mean? Calculated by what?

That really concerns me that you are questioning the 48" spacing as too conservative. There are of course many different situations, but if you consider soil pressure for a basement wall, wind load or seismic loads you would typically need 48"oc or possibly tighter for higher load situations.
Yes, if you have the best case situation of 90mph wind, no seismic, and no basement then 72" may work. I don't have the luck of designing in those areas since they typically don't require an engineer's stamp for residential.


Jim Houlette PE
Web:

http://www.evstudio.com

Online Magazine:

http://www.evstudio.info

 

[AELLC]

Jhoulette,

The AB spacings are calculated by Excel. There are no basements. These are one and two - story houses, 90mph wind, no seismic.

Most AB spacings are in the 16" to 48" oc range, but a few where we use gypsum shearwall can be 56" to 72", hence my OP.

We have a standard shearwall schedule that has default AB spacings but frequently the perforated shearwalls require AB spacings that exceed the spacing dictated in the schedule according to shearwall material and fastening.

Since these are production homes, we can't overspecify AB's.

 

[jhoulette]

Got it. Just checking, it got me concerned. Here in Colorado we don't run into many situations that allows the bolts much over 48".

On another topic, I design production homes as well. I would be concerned that the crews would be able to get the spacing right if several different walls have different AB spacing. A few extra ABs is a small price compared to any costs of adding more later.

But maybe you have better crews in your area. ;o)
Good luck!

Jim Houlette PE
Web:

http://www.evstudio.com

Online Magazine:

http://www.evstudio.info

 

[tajmeaw]

Section 2308.6 of the IBC 2006/2009, calls for anchors to be placed within a minimum of 4" and a maximum of 12" from the end of a plate/sill. Is this requirement only if you are using the prescriptive method or is this something that applies for all cases?

 

[woodman88]

Per section 2301.2 the design of the anchors design shall be either 1) ASD with sections 2304, 2305, 2306 or 2) LRFD with sections 2304, 2305, 2307 or 3) Conventional with sections 2304 and 2308.
So not to use section 2308.6 you would need to design your anchor per the ASD or LRFD requirements.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.