Two-Way Slab Design Based on ACI 318-11 using Finite Element Method

What is two way Slab?

When the ratio of long span to short span is less than 2, then the slab is known as a slab spanning in two directions or two-way slab.


—1. Choose layout and type of slab. Type of slab is strongly affected by architectural and construction considerations.
2. Choose slab thickness to control deflection.  Also, check if thickness is adequate for shear.
3. Choose design method.
Equivalent frame method- use elastic frame analysis to compute positive and negative moments.
Direct design method – uses coefficients to compute positive and negative slab moments
4. Calculate positive and negative moments in the slab.
5. Determine distribution of moments across the width of the slab.  Based on geometry and beam stiffness.
6. Assign a portion of moment to beams, if present.
7. Design reinforcement for moments from steps 5 and 6. Steps 3-7 need to be done for both principal directions.
8. Check shear strengths at the columns.