Cracked or uncracked capacities of Simpson STHD hold downs?
Cracked or uncracked capacities of Simpson STHD hold downs?
(OP)
In the 2011 Simpson catalog, where it lists the capacities of LSTHD/STHD hold downs, there are values under cracked that are in most cases lower than the values under uncracked.
Is this related to seismic governing, or what? Exactly what determines cracked or uncracked?
Is this related to seismic governing, or what? Exactly what determines cracked or uncracked?






RE: Cracked or uncracked capacities of Simpson STHD hold downs?
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
Does anyone ever do such an analysis?
I am also assuming the above applies to both wind and seismic (I don't have recent AC318)
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
For a PT slab, maybe you add your PT stress to the modulus of rupture? Not sure though...
Would you count hairline cracks from shrinkage as 'cracked concrete'? If that was the case wouldn't you always have to assume a cracked section?
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
I still don't know because what would be a rational analysis of actual bending moment in a continuous concrete wall footing and stem?
The footing is bearing on soil so that in the case of uniform load, then there would be no moment in the stem?
Where beams or girder trusses are putting a heavy concentrated load on the stem, how could it be practical to analyze all that, plus it is bearing on soil, which is to me a difficult support condition to analyze.
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
The highest-rated hold down (STHD14) has the same values for both cracked and uncracked, so it won't be a bother to downgrade the lesser hold downs.
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
RE: Cracked or uncracked capacities of Simpson STHD hold downs?
I suggest that the cracked values are values that can be relied on after a seismic event of a certain level. But as to what that level is, 6 or 7, you would have to call Simpson as suggested.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com