Load Duration
Load Duration
(OP)
I often see 1.33 load duration for masonry. What type of duration would this apply to?
Can a 1.6 wind load duration also apply to steel and masonry as it does to wood?
Thank you!
Can a 1.6 wind load duration also apply to steel and masonry as it does to wood?
Thank you!






RE: Load Duration
The 1.33 (1/3 stress increase) factor has traditionally been used for various materials other than wood. However, the new IBC building code does not permit this factor unless you have two or more "transient" loads applied....and it doesn't define what a transient load is so there is debate there about when to use it.
RE: Load Duration
MBones
RE: Load Duration
RE: Load Duration
I have stopped using the increased allowable stresses as that will be the standard in the near future here.
RE: Load Duration
RE: Load Duration
If you are using the IBC, then you will not be using the ACI 530 load combinations. The IBC's ban of the 1/3 increase will govern.
anyone disagree?
RE: Load Duration
RE: Load Duration
Does the increase only apply to wind, or can that also apply to seismic?
RE: Load Duration
http://www.strongtie.com/products/highwind/hw-load-determination.html
RE: Load Duration
When I follow the IBC, I have been using the basic load combinations "ASD". From those equations, I mult. the seismic force by .7 and compare to wind.
Specifically, using plywood shearwalls with 2x studs, a bit of confusion, to me, lies in section 2306.4.1 "The allowable shear cpacities.... in accordance with Table 2306.4.1 These capacities are permitted to be increased 40 percent for wind design."
I am wondering if others have taken an increase in table 2306.4.1 when using seismic forces? Or just for when wind is governing the design? Does APA comment on these increases when using ASD?
TIA
RE: Load Duration
The AISC ASD supplement that removed the 1/3 increase from the ASD 9th didn't come out until the end of 2001.
So shouldn't we still be able to use the 1/3 increase for steel in a dead plus seismic combination according to the alternate combinations in IBC 2000? Since the 1/3 increase wasn't removed from the ASD 9th until after the IBC 2000 came out?
The ASD supplement doesn't mention IBC 2000 alternate combinations being affected.
RE: Load Duration
you should look at boo1's link. Very helpful with those types of explanations.
However, I am asking about wood shearwalls which does have a 1.4 wind increase for shearwall capacities... I would like to know if others use this interpretation to justify this increase in capacity with regards to seismic?
RE: Load Duration
http://www.aisc.org/MSCTemplate.cfm?Section=Modern_Steel_Construction2&template=/ContentManagement/ContentDisplay.cfm&ContentID=24932
RE: Load Duration
RE: Load Duration
You may want to start a new thread. I believe there is a significant percent of forum participants that do not revisit threads for various reasons, such as, the original question has been answered, the thread is old ... There may be many who are not viewing your question!