Another question on ACI 318 App D
Another question on ACI 318 App D
(OP)
Would you ever expect concrete breakout to control in shera for an embed plate in teh middle of a wall, even a very thin wall?
I am picturing a wall supported by a footing. I don't see concrete breakout (for shear) even being a failure mechanism for this case, becuase teh wall is supported in the direction of the load. If the wall were hung from above (I know that's not realistic), I could see it failing like that. I just don't see an embed plate failing in concrete shear breakout in a wall.
Does anyone agree or disagree?
The problem I am having is that when you run through the numbers for it, Avco gets very big as you start getting large ca1 distances (as is the case for a wall with an embed plate 10' from the base of the wall). The problem is this, as ca1 gets large, Vb gets larger and Avco gets larger, and Avc also gets larger, but it adds very, very little to the capacity. Also, if you have a wall where the embed plate is 10' from the base, and in the middle of a 12'wide wall, suddenly your breakout is affect by three sides (technically) because ha (wall thickness), ca2, and (what I call) ca3 (which is the edge distance on the opposite side of ca2) are all less than 1.5*ca1 and you need to do all these other things. I just don't feel like this was meant to be the case.
Any thoughts?
I am picturing a wall supported by a footing. I don't see concrete breakout (for shear) even being a failure mechanism for this case, becuase teh wall is supported in the direction of the load. If the wall were hung from above (I know that's not realistic), I could see it failing like that. I just don't see an embed plate failing in concrete shear breakout in a wall.
Does anyone agree or disagree?
The problem I am having is that when you run through the numbers for it, Avco gets very big as you start getting large ca1 distances (as is the case for a wall with an embed plate 10' from the base of the wall). The problem is this, as ca1 gets large, Vb gets larger and Avco gets larger, and Avc also gets larger, but it adds very, very little to the capacity. Also, if you have a wall where the embed plate is 10' from the base, and in the middle of a 12'wide wall, suddenly your breakout is affect by three sides (technically) because ha (wall thickness), ca2, and (what I call) ca3 (which is the edge distance on the opposite side of ca2) are all less than 1.5*ca1 and you need to do all these other things. I just don't feel like this was meant to be the case.
Any thoughts?






RE: Another question on ACI 318 App D
I ran into similar issues last year. I griped to anyone who would listen that it doesn't make sense.
The problem is that essentially your shear capacity is proportional to Vb/Avco
Vb is a function of Ca1^1.5 and Avco is a function of Ca1^2.. see the problem?! The further away you are from the edge, the LOWER this ratio is.
However, ACI 318-08 has addressed this issue.
I suggest you purchase 08 if only for the improvements to Appendix D. Included in these improvements is a method to increase capacity by taking advantage of reinforcement existing in your concrete member.
RE: Another question on ACI 318 App D
RE: Another question on ACI 318 App D
RE: Another question on ACI 318 App D
I get a pryout capacity of 124K, a steel capacity of 68K, and a shear breakout capacity of 8.8K (no, that's not a typo). That can't possibly be right, can it?
The math is definitely right, it just doesn't make sense.
RE: Another question on ACI 318 App D
I've never said this before, but this is completely assinine!
RE: Another question on ACI 318 App D
It does have a limitation for certain h/d ratios.
RE: Another question on ACI 318 App D
RE: Another question on ACI 318 App D
Never, but never question engineer's judgement
RE: Another question on ACI 318 App D
Never, but never question engineer's judgement