Main reinforcement is the most important, load-bearing reinforcing steel in a reinforced concrete structure. It takes up the tensile forces that concrete itself can barely withstand, and lies in the direction where those forces are greatest — for example lengthwise at the bottom of a beam or at the bottom of a floor span. The remaining steel, such as stirrups and distribution reinforcement, supports the main reinforcement and holds it in place.
Why it is needed
Concrete is strong in compression but weak in tension. In a loaded beam or floor, tensile stresses arise, especially at the underside in the span and at the topside over the supports. There the structural engineer places the main reinforcement, so that the steel takes up the tension and the concrete the compression. Together they form a strong whole.
Points to note
- Position — the main reinforcement must lie in the tension zone; wrongly placed steel does not contribute
- Concrete cover — there must be enough concrete around the steel against corrosion and for fire resistance
- Anchorage — the bars must run on and anchor sufficiently, otherwise they pull loose
Never drill or chase into a concrete structure at random: if you hit the main reinforcement you weaken the load-bearing capacity. Have a structural engineer check.
Related terms
- Reinforcement
- Reinforcing steel
- Reinforced concrete
- Concrete cover
- Additional reinforcement
- Beam
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