Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Concrete Design
	Subarea:	Slab Design
	Original Author:	Bentley Technical Support Group

I am trying to define a Slab Design brief from within the RC Designer ( Concrete Design mode ). The Main Reinforcement tab refers to directions like X and Y. How do I know which directions are these referring to and can I change it ? Also what does the terms “Top/Bottom” and “Outer” bars represent ?

As far as X and Y direction are concerned, these are displayed on the slab itself when you go to the Concrete slab > Summary page within RC Designer. You can always change the direction of X and Y, if you want to, by going to the menu option Slab > Slab Axes. The resulting dialog box would provide option to define the X direction either by selecting two existing slab nodes or by selecting a component plate, in which case the X is aligned along the local X of the selected plate. Once you make the change, the graphics may not refresh. To refresh it, right click on the graphics window, choose Diagrams > General > uncheck the box for Design Axis> click Apply which should remove the axis plot. Now recheck the Design axis check box and click Apply. You will now see the modified orientation of X and Y. Outer bar simply denotes the bars which are closest to the top and bottom faces of the slab. Once the X and Y are established, you can use the right hand rule to find positive Z. The face in the direction of the positive Z would be the top face of the slab just like in STAAD.Pro. The opposite face would be considered the bottom face.

So if you have Outer bar direction set to “X” under Top Bar Criteria, it means that for the top face of the slab, the bars which are placed nearest to the face, are oriented along the X direction. The bars in Y would be inside the X direction bars.