calculating "d" in a r/c wall

[arh13p]

I have a 10" wall with vertical steel located in the middle. I am checking to see if it matters what side the contractor ties the horizontal steel. when calculating "d" for both locations, if the steel is located on the tension side, do I need to substract db for the vertical steel along with 1/2db of the horizontal steel or just ignore the vertical steel all together? thanks.

 

[CANPRO]

I'm not sure I follow your question...

"if the steel is located on the tension side"...the steel is always on the tension side...thats why its there.

Your distance 'd' is from the outside of the compression face to the centre of your tension reinforcment...if you need to subtract the diameter of your vert. steel to figure out that distance then thats what you do.

As far as which side your horizontal steel is on...if its just there for temp/crack control then I really don't think it matters.

If your horizontal steel is there because of bending then I would suggest putting it on whatever side gives you the largest 'd'

 

[arh13p]

sorry I worded that poorly. I am sizing steel based on the bending moments. I want to take a conservative approach in sizing my hortizontal steel so it won't matter which side they tie the steel too. hope this make more sense.

 

[msquared48]

So you are spanning the wall horizontally rather than vertically?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[arh13p]

Its a 8' wide, 24' long, 8' deep tank with an open top.

 

[Lemony]

Depends on if you are designing for seismic forces. I believe ACI let's you use 0.8*L if not, but that is for shear. For bending look up the Cardenas procedure.

 

[rowingengineer]

make sure you have enough steel for shrinkage ect.

http://www.nceng.com.au/

"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected” Petroski 1992

 

[delagina]

caneit already answered your question

 

[PSlem]

If the tank is for liquids check ACI 350, not 318, for minimums.

 

[UcfSE]

If you want it to not matter which side the GC ties to, use the smaller d for both directions of bending, in and out of the wall plane.

 

[ztengguy]

Or show on your drawing that you want the steel in a certain location, thats what most other engineers do, so they can build it properly.

 

[rapt]

Lemony ,

.8 L is only fopr PT design and it requires a lot of PT steel at the tension face, not in the middle (indirect requirement as the test is is based on were pretensioned beams with strand at minimum cover to the tension face!)

For RC, use the smaller d if you want to cover bad installation, or the possibility of bending in both directions (eg swimming pool where soil pressure/external water pressuse could give tension on one face while internal water pressure could give tension on the other face)!

 

[BAretired]

A single middle layer of steel may meet code requirements, but for a water retaining structure, I believe you should have two layers, one near each face.

BA

 

[Lemony]

Rapt,

Please refer to ACI 318-08 11.9.4. And again, that is for shear design.

 

[Brad805]

I agree with BA. If this is a water retaining structure strength rarely controls the design. Crack control is far more important. Even if it were the controlling factro I would use the more conservative approach so that if the contractor does his own thing locating the bars we do not end up in a lengthy debate.

Brad

 

[msquared48]

No top?

OK, the 8 foot wide end walls can span horizontally, but not the 24 foot side walls. These need to be fixed at the base and span vertically with the steel placed so as to resist both the max soil load with no water, and the max soil load with the water. You will also need to use waterstops at the base of the wall.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BAretired]

You might find the following link helpful.

http://www.mde.state.md.us/programs/Water/DamSafety/TechnicalReferences/Documents/

http://www.mde.state.md.us/assets/d...Structural Engineering presentation_Gene.pdf

BA

 

[rapt]

Lemony ,

That is for longitudinal shear and is based on the length of the wall.

arh13p's question related th transverse bending!