Kevin Kosta
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Concrete beam analysis.

Enter a rectangular section to explore its bending resistance. Change an input to recalculate the result.

Reinforcement layout

Section geometry

Design strengths & action

Use design strengths you have already determined for your exercise. Positive bending only; bottom steel is in tension.

Section result

Singly reinforced
Flexural resistance— kNm

—

Neutral axis, x—
Relative depth, x/d—
Steel strain, εₛ—
Steel stress, σₛ—

Section geometry, compression zone and neutral axis; two dots represent each steel layer. h d Aₛ Compression zone Tension steel

Section schematic · dashed line: neutral axis x · shaded area: compression zone. Bar count and size are symbolic; extreme aspect ratios are adjusted for clarity.

Calculation steps
  1. Force equilibrium—
  2. Concrete compression, Cc = 0.8 fcd b x—
  3. Moment about tension steel, MRd—

Educational section analysis using plane sections, εcu = 3.5‰, Es = 200 GPa and a rectangular concrete block of depth 0.8x at fcd. Steel stress follows compatible strain, capped at ±fyd. The fixed block parameters represent normal-strength concrete (up to C50/60); high-strength concrete is outside this model. The gross concrete block neglects the small area displaced by compression bars. No axial force is included. Steel rupture and ductility limits are not checked. This checks flexure only; it does not check shear, detailing, minimum or maximum reinforcement, serviceability or the current national annex. See JRC worked examples ↗