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In a liquid-filled tank, must construction joints in the wall align with the construction joints in the slab? These are construction joints, not contraction joints--i.e., continuous reinforcement. Specifically, this is for a circular tank, and according to the specs, the slab will be placed in...

Why is portland cement 94 #/cf alone (SG=1.51), but is 197 #/cf (SG=3.15) when used in a mix design?

Thank you, hokie. I was feeling like the guy who tells a joke and hears only crickets. That is, in fact, the brace--installed parallel to the wall. You know, because it would just be in the way if they brought it out from the wall. Jokes aside, though, concretemasonry, thank you for the tip...

I was a little worried, because I could not find any temporary bracing for these 28 ft cmu walls. Luckily, though, I finally found this. Enjoy. . . .

Thanks to all for the responses. The bottom line is this tank has to be in use for 50+ years, and has to be watertight. I don't like being the unreasonable engineer, and I always try to work with contractors to resolve issues like these, but this is a big one. What he wants to do might work...

I think bond would be okay, because the surface is so rough. I could require a bonding agent, as well. The thickened slabs under the walls will act in flexure, but the slab itself won't see much. What really concerns me most is: a)the roughness that gives me the bond could cause cracking in...

It's very good soil, mostly caliche at this depth. Groundwater is not an issue.

. . .40 yards into a 200+ yard pour for a section of slab in a carousel aeration basin. Now a large section of the slab has about half the thickness in place, with most of the top mat of steel exposed, and some of the bottom mat exposed. They at least had the quick-thinking to 'spread out'...

Try Diamond Dowels from PNA Construction Technologies. www.pna-inc.com These are for shear transfer, not tension or moment.

vincentpa, I disagree that 10.5.4 is "quite clear". It says to use the minimum required by 7.12, but again, 7.12.2.2 says to distribute the temperature and shrinkage reinforcement to each face, so I don't think it's telling us to use the entire 0.005 on each face. Take a 12" wall, d=9"...

I think 10.5.1 does apply, because it says "At every section of a flexural member. . .", which, for a tank, includes walls. So (10-3) applies for each face, and not less than 200/fy. Also, it need not be greater than 4/3 that required by analysis, per 10.5.3. However, the reinforcement...

I was of the belief that if you satisfy your flexural requirements, you then compare the total amount of steel to your temp/shrinkage minimum, for the whole section. However, 10.5.4 of 350 seems to suggest that you should have the minimum temp/shrinkage on each face. Now, after re-reading...

Section 17.5 provides a fairly straightforward analysis method, without having to calculate Q. Specify that the cold joint is roughened to 1/4", and you can get pretty decent capacity using the stirrups you already have there. There is a limit to the available capacity, beyond which you will...

That's what confuses me. Article 1.10.1 says it applies to masonry designed in accordance with section 2.2 or Chapter 5. However, section 2.3.3.4.5 says "Beams shall be designed to meet the deflection requirements of Section 1.10.1." Then in the commentary, it contradicts itself again. So...

ACI 530 requires a maximum deflection of L/600, or 0.3" max, for a beam or lintel supporting masonry. csd72, I'm with you when the span makes that seem impractical, but how do you interpret the code requirement (assuming you are in the US)? I designed one of these almost exactly as Gordy2...

Chapter 17 of ACI addresses this. Double-dipping is permitted. I've got a similar condition, except it hasn't been constructed yet. The contractor is proposing to pour the monolithic slab and beam in separate pours, so I have to investigate the horizontal shear.

Females were a predictably small percentage of my classmates in Civil, fewer still that focused on Structural. However, my first job was working for a female sole proprietor. I left that job for one where I briefly worked under a female, who later went on to start her own firm. Now, at my...

Is that the title you're looking for? I'm not familiar with it. However, PCA has some good books on concrete tanks: "Rectangular Concrete Tanks" and "Circular Concrete Tanks Without Prestressing." www.cement.org

We have it in the specs, but not by name. I don't recall the exact verbiage, but it basically forces them to use soff-cut. Most of the contractors in the area now have it, so it's not the issue it used to be.

I don't know anything about cofferdams, but Section 22 has the modulus of rupture as 5*sqrt(f'c). Section 9 has it as 7.5*sqrt(f'c), but for structural plain concrete, Sec. 22 governs.