Expert: Bill DeShawn - 5/19/2011

Question
Hi there!
I'm currently working in concrete rebar (steel in concret) and I was wondering if it was possible in AutoCAD 2007 to add a proprety to calculate something for me? For example, I've drawn a simple line illustrating the length and direction to where I want to place some rebar, let's say the bar is 12'4". Now on the plan it is indicated that I need to place bars every 12" maximum. So by hand I know that I need 14 bars. Now is it possible to make this simple calculation in autoCAD 2007 so that if I select the 12'4" line, it will automaticaly tell me 14 bars in like the proprety window or something.

So having this in mind, I would then create another one for let's say 16"c/c, 20"c/c, etc so that I if the spacing changes I can quickly get the number of bars needed.

Thanks in avance!

Answer
Marc,
not exactly, because there isn't a "property" that will know what the boundaries of your slab are.  However, I was working on a LISP routine for you today.  And since this isn't a private message, anyone who would like to download this, may click on the following link or paste the text to their browser window to download the routine.  Create a line on the layer of your choice that will be the model line for all the lines you want to represent the rebars within the slab. The routine will ask you to select the one and only rebar line that you drew in the slab boundary, then it will ask you to select the boundaries that are to each side of the line so it can then create an array of those lines to fit within the boundaries.  You will then be asked to select a direction for the array.  If the boundary width is a multiple of the distance between one side of the boundary and the other, you will need to erase the last object in the array.  Otherwise you will be asked to move the new array of lines to one side or the other just a little bit in order to center them within the boundary.  

Now suppose you wanted just to make a note of how many bars it would take to spread the steel from one side to the other and you didn't want to actually draw them.  If that's the case, let me know, and I'll edit the routine so that it puts a note above the line that says "(20) #_____ HORIZ. REBAR" (you can chg an attribute for the blank value.  "(20)" will be automatically changed to what actually is needed as found by the routine.  For that, however, I would need a sample drawing from you to be able to get layer, text style and height information to include those settings in the routine.  It would also put a note below the line with the spacing information.  And correct me if I'm wrong, but to my knowledge, the note would read O/C or O.C. for "ON CENTER" instead of "C/C".  Is that not correct?

 I made the routine to work within rotated UCSs just in case you run into that.

You can find the routine here:
http://my.sterling.net/~bdeshawn/slabrebar.lsp

Keep in touch
Bill DeShawn
http://my.sterling.net/~bdeshawn