Steel–concrete composite beams

What this module covers

• Explain composite action physically, in terms of where the neutral axis moves
• Calculate the plastic moment of a composite section and say which case is efficient
• Say what a shear stud has to do and the two ways it can fail
• Explain why partial shear connection is legitimate and often economic
• Separate the construction stage from the composite stage, and say which governs
• Explain why an unpropped beam's deflection cannot be calculated in one go

Lessons

1. 11.1

   How composite action works, and what it buys

   The slab is already there. Connect it to the beam and the two act as one section — with the concrete doing what it is good at and the steel doing what it is good at.

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2. 11.2

   The construction stage, and why deflection needs three calculations

   Before the concrete sets, the beam is bare steel carrying wet concrete with nothing holding it sideways. That stage frequently governs — and it leaves a deflection behind that never goes away.

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