Chapter 7

Question 1

What defines a Two-Way slab?

Answer 1

• aspect ratio <2
• relative stiffness of beams in 2 directions is more than 0.2 and less than 5
• columns are not offset by more than 20% the span
• reinforcement is placed in an orthogonal grid

Question 2

What can you do if slab thickness does not meet strength requirements?

Answer 2

• Add column capitals
• Add drop panels
• Increase thickness
• Increase column size
• Increase concrete strength
• Add beams

Question 3

What are the 6 limits on using the Direct Method?

Answer 3

1) Min of 3 spans
2) Spans must be relatively equal, not differing by more than 1/3longest span
3) uniform load Wfl/Wfd<2
4) rectangular slab, aspect ratio<2
5) The relative stiffness of the beams in the 2 perpendicular directions must be greater than 0.2 and less than 5
6) Columns cannot be offset by more than 20% span