IntermediateTopic 53 of 112Civil & Structural
Design of RC slabs
One-way and two-way slabs depend on support conditions and aspect ratio.
In depth
One-way slabs span mainly in the short direction (L/B>2) with distribution steel across; two-way slabs span both, using moment coefficients. Minimum thickness L/20–L/30 by deflection control. Flat slabs, waffle slabs and post-tensioned slabs suit large spans; punching shear needs checking.
Key points
- Cover and spacing
- Edge conditions
- Punching at columns
ExampleA 125 mm one-way slab spans 3.5 m between beams.
What is Design of RC slabs?
One-way and two-way slabs depend on support conditions and aspect ratio.
Why is it important to understand design of RC slabs?
Slab design depends on how the slab is supported, so knowing whether it spans one way or two ways saves steel and avoids errors.
When does a slab act one way?
When the length to width ratio is greater than about two, so most of the load travels in the short direction.
What is span to depth ratio?
A simple deflection check that relates the span to the effective depth, and it gives a quick check before detailed calculation.
How is Design of RC slabs used in practice?
Typical applications include choosing reinforcement for a one-way floor spanning between beams, designing a two-way slab supported on four sides and checking the deflection of a slab with a long span-to-depth ratio.
What should I learn before Design of RC slabs?
Study "Design of RC beams" first (topic 52 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Design of RC slabs?
Cover and spacing. Edge conditions. Punching at columns.
Can you give an example of Design of RC slabs?
A 125 mm one-way slab spans 3.5 m between beams.
What comes after Design of RC slabs?
The next topic is "Design of RC columns", which builds directly on this one.
How difficult is Design of RC slabs?
It is classed as Intermediate in Civil & Structural (topic 53 of 112). It is an intermediate topic. Work through the beginner topics in Civil & Structural first.