shearwall-multiple hold downs
shearwall-multiple hold downs
(OP)
hi,
I'm trying to spread uplift (5kips) with 2 hold downs per side (this is just an example).
Is there a simple way to determine what would be an uplift if I use 2 hold downs?
thanks alex
I'm trying to spread uplift (5kips) with 2 hold downs per side (this is just an example).
Is there a simple way to determine what would be an uplift if I use 2 hold downs?
thanks alex





RE: shearwall-multiple hold downs
I would be careful to check rebar in stem wall, and make sure that uplift is resolved all the way to footing.
RE: shearwall-multiple hold downs
Each hd gets 2.5 K
RE: shearwall-multiple hold downs
from risa (i put 10kips) there is a difference. Just wondering where it's coming from.
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
Uplift = lateral shear x wall ht divided by wall length.
Are you a degreed engineer?
RE: shearwall-multiple hold downs
I would be concerned with not utilizing the full capacity of either hold down if they are placed too close together. And if they are spread further apart, some of the leverage is lost.
As for the difference in the results, perhaps Josh Plum could comment on that. You might reconsider posting this in the RISA Technologies forum if you do not get the answer you seek. Josh is in there more and is the resident expert. You would have to red flag this string first before doing that though.
Mike McCann
MMC Engineering
RE: shearwall-multiple hold downs
IMO it is being mis-applied for a simple shear wall.
RE: shearwall-multiple hold downs
Look at what happens when you have HDU in a short shear wall, now that is major loss, not in an 8' wall such as the OP>
RE: shearwall-multiple hold downs
It's always a little problematic putting in two perfectly rigid supports so close to each other. Therefore, you might either do a hand calc (like AELLC suggests), or replace the perfectly rigid reaction with a more flexible spring support.
The real behavior of a shear wall is actually a lot different than that model. You have continuous shear resistance along the length of the wall. You have continuous compressive vertical resistance along the wall. Heck, you probably have something close to contiunous tensile resistance as well. The NDS stiffness and deflection equations assume this type of continous resistance as well....we just don't rely on it for design purposes. Instead, we create a pretend force couple in the chords to resist the total moment. At least that's the current "standard of care" in the industry. If you do something else (however rational) then you probably want it to be more conservative than what the hand calc method would give.
RE: shearwall-multiple hold downs
½(10000 lbs)(10)/10=5000 lbs
½(10000 lbs)(10)/8=6250 lbs
What are the horizontal reaction?
If the holddowns are on the same chord member, taking 1/2 the load to each holddown is reasonable. If each holddown is on a separate chord, more analysis may be warranted. I would be interested to see the result if the tension holddowns are modeled as springs. For a spring constant, I would start with k= hold down capacity/ holddown slip.
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
I have about 11 kips uplift in 3 story condo shearwall. Capacity of 7/8" hilti HY200 in 8" conc wall about 6kips
that's the reason I'm trying to have 2 hold downs on separate chords(16" apart).
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
Are you hooking into a typical spread footing or turn down slab?
RE: shearwall-multiple hold downs
RE: shearwall-multiple hold downs
Mike McCann
MMC Engineering