IntermediateTopic 59 of 112Civil & Structural
Composite structures
Steel and concrete working together increase strength and stiffness.
In depth
Steel beams connected by shear studs to a concrete slab act compositely, increasing stiffness and strength. Also concrete-filled tubes, composite columns, and profiled decking. Transformed-section method and plastic design are used. Reduces steel weight by 20–30%.
Key points
- Shear connectors
- Effective slab width
- Construction stage checks
ExampleOffice floors use steel beams with 130 mm composite slabs on metal deck.
What is Composite structures?
Steel and concrete working together increase strength and stiffness.
Why is it important to understand composite structures?
Composite construction uses steel and concrete together so each material works where it is strongest, which saves steel and increases stiffness.
What makes composite action work?
Shear connectors transfer horizontal shear between the steel and concrete, so they act together as one section.
What is the advantage of composite beams?
They are much stiffer than the steel beam alone, which allows lighter sections and longer spans.
How is Composite structures used in practice?
Typical applications include designing a composite floor beam with a concrete slab on steel decking, using shear studs to connect a slab to a steel girder in a bridge and increasing the span of a steel beam by adding a concrete top slab.
What should I learn before Composite structures?
Study "Steel connections" first (topic 58 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Composite structures?
Shear connectors. Effective slab width. Construction stage checks.
Can you give an example of Composite structures?
Office floors use steel beams with 130 mm composite slabs on metal deck.
What comes after Composite structures?
The next topic is "Timber design", which builds directly on this one.
How difficult is Composite structures?
It is classed as Intermediate in Civil & Structural (topic 59 of 112). It is an intermediate topic. Work through the beginner topics in Civil & Structural first.