As novice Rebar Shop Drawings Detailer 1

[SaintShopDWG]

Hi All,

I am novice Rebar Shop Drawing Detail (meaning this something I want to do). I am currently reviewing ACI and CRSI manuals for rebar detailing but I am having little bit of difficulty with calculating rebar spacing. Does anyone know where I can find someone that can tutor me on the issue?

 

[BulbTheBuilder]

You can start with concrete textbook on the basics. Most textbooks show how to get area, spacing, and number of reinforcements.

If you are interning at a shop, you can directly ask people around you "how to read shop drawings", "how you to get the spacing", "how reinforcements are placed", and others.

Let's assume you have a 24' wide slab with 28#4 reinf. The number of rebars = (24'*12in/ft)/28 = 10.28". Hence your spacing is 10"

*key things, for quantity of rebar if you get 27.3, round up to the nearest whole number which 28. The reason you can't place 27 and a fraction along the length so you add 1.

***For spacing, if you get 11.7", round down to the nearest "constructable" number like 11.5" not 12". You need the 11.7" (smaller spacing) for structural integrity so you can't exceed 11.7".

 

[SaintShopDWG]

Thank you for responding to my message. I appreciate your time. Your example was helpful. I have many text books on the subject. Currently, I am studying ACI SP-17, ACI Detailing Manual and CRSI Reinforcing Bar Detailing Text book. Moreover, I feel like I have a fair understanding for interpreting the drawings. Where I get lost is the math for spacing. For Example in the image below when I do the math for 10 spaces @ 6 3/8"+/-. One of the bar end up in the required cover. Math wise, I understand the theory but it doesn't match up with the drawings. The text book provide acceptation and rules for spacing. I am still a little confused on when the math does not match the drawings what to do.

 

[BulbTheBuilder]

You're welcome, SaintShopDWG! Those are excellent resource materials, and I even refer to them sometimes. The "+/-" symbol is there to indicate approximate dimension. Most time, you will get the dimensions exactly on the field, just like what you indicated in this image. For this case, one or two of the reinforcements will have a spacing lesser than 6 3/8".

The engineer designs a footing and calls out say #5@6 3/8". The 6 3/8" is indicated on the drawing to show the limit when it comes to spacing.
On site, they will place the edge reinforcement first to maintain their 3" and distribute the rest of rebars 6 3/8" c/c (center to center). As they get the last edge of the last reinforcement, placing additional rebar gives a spacing lesser than 6 3/8".

As long as the spacing and number of rebars requirement are satisfied, we are good. I hope this with logic.

 

[SaintShopDWG]

Thank you, This information was very helpful.

 

[BulbTheBuilder]

You are welcome!