ACI Section 11.5.4.3
ACI Section 11.5.4.3
(OP)
Greetings,
I have a question pertaining to Section 11.5.4.3 of ACI 318-02. It states that when Vs exceeds 2 Vc, then maximum spacing limit shall be d/4. In case an engineer decides to put more shear steel than necessary, does ACI force section 11.5.4.3 into effect? Because the way Vs is defined, it is not the required shear steel but provided shear steel. It almost seems that the code is penalizing you for being conservative, or am I missing something?
I have a question pertaining to Section 11.5.4.3 of ACI 318-02. It states that when Vs exceeds 2 Vc, then maximum spacing limit shall be d/4. In case an engineer decides to put more shear steel than necessary, does ACI force section 11.5.4.3 into effect? Because the way Vs is defined, it is not the required shear steel but provided shear steel. It almost seems that the code is penalizing you for being conservative, or am I missing something?






RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
I have a 48" wide x 16" deep beam
Phi Vc = 74 kips (d=14.5")
Av using a spacing of 4" o.c. = 0.809 in2
If I use 4 #4 ties, Av = 1.2 in2. That gives me Vs = 261 kips > 2Vc, and hence I am forced to use a spacing of 3" o.c.
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
Also, you are not required to check deflections unless the depth of your section is less than that given in table 9.5(a) of ACI 318-05.
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
RE: ACI Section 11.5.4.3
I suppose a more accurate expression for this limit would be,
"Where (Vu/phi - Vc) exceeds 4 sqrt(f'c) bwd ..."
Also, Vc isn't necessarily 2 sqrt(f'c) bwd so the limit doesn't always boil down to 2Vc. You're right though that the general idea is that if the required strength is more than twice the concrete component (originally assuming 2 sqrt(f'c) bwd) then the spacing should be halved since the stirrup strength dominates.
If they did want to assume that Vc = 2 sqrt(f'c) bwd for the sake of this limit then it could be simplified to,
"Where Vu exceeds 6 phi sqrt(f'c) bwd ..." (Vu > 3 phi Vc)
RE: ACI Section 11.5.4.3