The Beam Selection Helper picks an appropriate Indian Standard rolled section (ISMB / ISWB / ISHB / ISMC) for a given simply-supported or continuous beam, based on span, applied UDL, and steel grade. It applies IS 800:2007 Limit State design (LRFD) — checks moment capacity, shear capacity, and deflection serviceability — and returns the lightest adequate section plus a safety margin.
Use it during preliminary design to size beams before detailed analysis, during retrofit to confirm an existing section is still adequate, or as a teaching tool for IS 800 limit state checks.
M_d = β_b × Z_p × f_y / γ_m0 where β_b = 1.0 for plastic / compact sections, 1.0 × Z_e/Z_p for semi-compact, < 1.0 for slender (effective section). γ_m0 = 1.10 (resistance factor for yielding). The calculator first classifies the section per Cl. 3.7 (b/T_f and d/t_w ratios), then applies the right β_b. For Class 4 slender sections, an effective section modulus is used — but the helper limits its picks to Class 1 / Class 2 to keep design simple.
For laterally unrestrained beams, M_d is reduced to M_d_LTB = β_b × Z_p × f_bd / γ_m0 where f_bd is the design bending stress from Table 13 / Table 14 / Cl. 8.2.2.1. The helper assumes lateral restraint at supports + at midspan (reasonable for typical floors with deck-on-steel) — if your beam is unrestrained over its full length, apply manual LTB check.
V_d = A_v × f_y / (√3 × γ_m0) where A_v = (D − 2T_f) × t_w for rolled I-sections. Shear interaction with moment per Cl. 9.2 if V > 0.6 × V_d (rare for typical UDLs).
Live load deflection ≤ Span / 360 (typical residential / office), Span / 240 (industrial), Span / 200 (cantilever). For UDL on simply-supported: δ = 5wL⁴ / (384 EI). The helper computes this and flags 'Deflection governs' if so — in which case a deeper section (more I) is required, even if moment / shear are OK.
Factored UDL: 30 × 1.5 = 45 kN/m (LSC). Max moment: 45 × 36 / 8 = 202.5 kN·m. Required Z_p = M / (f_y / γ_m0) = 202.5 × 10⁶ × 1.10 / 250 = 891 cm³. ISMB 350 (Z_p = 889 cm³) — marginal. Pick ISMB 400 (Z_p = 1,290 cm³, 61.6 kg/m). Check shear: V_max = 30 × 6 / 2 × 1.5 = 135 kN; A_v = (400 − 2×16) × 8.9 = 3,275 mm²; V_d = 3,275 × 250 / (√3 × 1.10) = 430 kN >> 135 OK. Deflection (service): δ = 5 × 30 × 6,000⁴ / (384 × 200,000 × 20,458 × 10⁴) = 12.4 mm = L/484 < L/360 OK. Pick: ISMB 400, weight 369 kg total (61.6 × 6). Code reference: IS 800:2007 Sec 8 + Sec 5.
ISMB is lighter than ISWB at the same depth (narrower flange), so for pure flexure with adequate lateral restraint, ISMB is more economical. ISWB is preferred when LTB is critical (long unrestrained spans, narrow building widths) — its wider flange increases lateral stiffness. The helper's default assumption is restrained-at-midspan, which favours ISMB. If you toggle 'unrestrained' it switches to ISWB / ISHB picks.
LRFD (Limit State / Load and Resistance Factor Design): IS 800:2007. Apply load factors (1.5 for live load, 1.5 for dead load × 1.2 etc.) and resistance factors (γ_m0 = 1.10) separately. Failure when factored load > factored resistance. ASD (Allowable Stress Design / Working Stress Method): IS 800:1984. Apply working loads, compare against permissible stresses (60% of yield for tension, 66% for shear). ASD is being phased out — IS 800:2007 is the current code, mandatory for new design.
The current version handles simply-supported beams only. For continuous beams (negative moment over supports), use a frame analysis to get max positive and max negative moments separately, then apply the helper twice (one for span moment, one for hogging at support). Negative-moment region typically governs for span < 8m.
Composite design (IS 11384) is outside this helper's scope. For composite beams, the steel section provides only ~60% of the moment capacity — the slab + shear connectors do the rest. Use a dedicated composite design tool or refer to IS 11384 / Eurocode 4 for full procedure.
Not by default. For long spans (> 8m) or heavy live loads, IS 800 Cl. 5.6.2 recommends camber to compensate for dead-load deflection. Camber = δ_DL = δ from dead-load only. Mill camber is typically set to L/500 to L/750. The helper outputs δ_DL separately so you can pick a camber if needed.