Module 09
Reinforced-concrete slabs
One-way and two-way action, flat slabs and the punching failure that gives no warning, yield lines, and stairs — where the load is not where you think it is.
What this module covers
- Derive how a two-way slab shares its load, rather than looking it up
- Decide when a one-way idealisation is justified
- Design a two-way slab, and recognise when minimum steel governs
- Check punching shear at a flat-slab column and say why it is the critical failure
- Explain yield-line analysis as an upper-bound method, and why that matters
- Load a stair correctly, allowing for the slope
Lessons
Why a slab chooses a direction, and why the choice is decided by the fourth power of the span ratio.
Start lesson →The failure that takes buildings down, and the analysis method that finds more capacity than there is if you let it.
Start lesson →
Module checkpoint
Check what you have taken in
6 questions
Question 1
A panel is 3.5 m × 5.0 m. What fraction of the load goes the short way? Give the decimal.
Question 2
Why is yield-line analysis described as an upper-bound method?
Question 3
A 5.0 m square simply supported slab is reinforced with m = 20 kNm/m. What collapse load does yield-line analysis give, in kN/m²?
Question 4
A 200 mm slab has 25 mm cover and H12 bars in the outer layer. What is the effective depth to the outer layer, in mm?
Question 5
A punching check fails, and the stress at the COLUMN FACE also exceeds vRd,max. What is the correct response?
Question 6
A stair has a 175 mm waist, 250 mm going and 175 mm rise. What is the slope factor applied to the waist self-weight?