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Appendix D of ACI 318-08 provides formulas for calculating the projected concrete failure area, ANC on page 421 for varying number of rods. These formulas are to calculate the ANC when ALL of the rods are in tension, i.e. when ALL the rods are experiencing uplift when in the process of being...

I think I just had a light bulb moment! All of us have been going on about "minimum steel", starting with my initial inquiry about the placement of "minimum T&S" steel. However, most of the time, in the subsequent posts, we do not actually specify whether we mean "minimum flexural steel, i.e...

Thank you so much for your response, hokie66. It really helps me to understand the underlying principles behind the footing design. Ok, you said, "The assumption in providing T&S reinforcement is that the whole thickness of the section is in the same stress state, so the reinforcement can be...

Is anyone willing to take a stab, that if all my combined footing requires is minimum flexural steel, then why the reinforcement cannot be "split" between the top and bottom faces? What is, or are the main reason(s) for this? Do the top and bottom bars, say parallel to the long direction, not...

Sorry for not being more clear earlier. I do have two columns on my spread footing. I am providing reinforcement on both the top and bottom faces, in this case, it is minimum reinforcement. From the discussion above, I will provide minimum reinforcement in EACH direction, TOP and BOTTOM. Two...

Thank you very much for all the wonderful responses which are bringing some clariy to a seemingly "easy" topic, but can still be confusing to a lot of engineers. I have got a follow-up question based on herewegothen's response; which is the tension face of the footing. I hope all of you, esp...

StructuralEIT, thank you so much for your prompt response, as always. BTW, there is not Section 14.4.4 in ACI 318-05. Section 14.4 is on Page 239. Did you mean Section 14.3.4? My 35" footing is for illustrative purpose for this question only. What would be your best solution for the question...

I have got a question about the placement of minimum temperature and shrinkage steel, say for a 35" thick rectangular footing 14 feet long and 5 feet wide. Let's say, that all I need for my footing is minimum temperature and shrinkage steel. Hence, Ast = 0.0018bh = 0.0018 * (14*12) in * 35 in =...

marinaman: You hit the nail right on the head! Yeah, the hair pin ties are used for a foundation designed for a pre-engineered metal building (PEMB), or a metal building system (MBS), as it is called nowadays. Are PEMB's or MBS's where hair pin ties are mainly used? I have not really used...

Per ACI 318-08 D.5.3.5 - The pullout strength in tension of a single hooked bolt, Np [shall not exceed]: Np = 0.9 * f'c * eh * da, where 3 da <= eh <= 4.5 da ( <= means "less than, or equals to") eh = distance from the inner surface of the shaft of a J- or L-bolt to the outer tip of the J-...

kslee1000, Thank you so much for providing that post and taking the effort to provide that sketch. It is surely appreciated and helps a lot in the discussion. BTW, ACI 318-08 also presents the same drawings as "Failure modes for anchors" in Fig. RD.4.1 on Page 415. BAretired, ACI 318-08...

Correct me if I'm wrong, but whenever I've designed anchor bolts, I have mainly designed for: 1. Breakout strength 2. Pullout strength 3. Side-face blowout strength, and 4. Pryout strength I am going pretty much by Appendix D of ACI-318. In my particular case, I did not design for side-face...

I have got a question about the design of a group of four anchor bolts that are tied with hair pin ties. My hair pin ties are #7 bars and about 6'-6" long. They are in the shape of V with a "flattened bottom". The "flattened bottom" is pointed towards the outside of the slab and hooked around...

I have an exterior concrete spread footing, say 10' x 10'. The thickness is 3', say. My column is 2' from the edge of the footing. Therefore, my actual eccentricity, e is 10'/2 - 2' = 3. Now, I have been told that my eccentricity - the calculated eccentricity, that is - can be less than the...

Thank you very much, jheidt2543 and kslee1000. I've got two questions, though. One is, what is the best way to evaluate the footing overlap influence area? Would this be a factor if I design a combined footing, or would it only be a factor if I design two separate footings. Why would two...

I have got a general question about the design of a combined footing vs. a single footing. I have just finished a design of a single footing for a storage silo. It is founded on grade, with a soil bearing capacity of 3 ksf. My footing will be a 19 ft by 19 ft by 3 ft thick footing, reinforced...

Avc, as defined in ACI 318 Section D.6.2, is the projected area of the failure surface on the side of the concrete member at its edge for a single anchor or a group of anchors. Now, my aim is to calculate the concrete breakout strength of anchor in shear. ca1 is the distance from the concrete...

Thank you so much, jike. That really helped, and now I can move on with the checking.

I am checking the concrete strength of my footing, and came across this formula for the nominal moment of a one-foot section of my footing: Mn = 5 * (fc')^1/2 * S S = section modulus Could someone please verify the validity of this formula, and where is this formula stated, i.e. provide some...

Thanks for the support, NS4U and for the practical example you provided. Even though a reduction of 50% (NS4U's example with area of steel) and a reduction of 43% (NS4U's example with steel capacities) are reasonably close, they are not exactly the same, and the variance may be even more if the...