What prerequisites do I need for Beam Design Workflow?

You should be familiar with the relevant structural steel design code, have your project loads and geometry defined, and understand the limit states you need to check. The guide walks through each step with code references — have the applicable code edition available for verification.

Can I apply this guide to any steel design project?

The guide covers standard design procedures that apply broadly to steel structures. However, project-specific conditions (unusual geometry, dynamic loading, high-temperature service, fatigue, seismic demand) may require additional checks beyond the scope of this guide. Always consult the full code text for your project.

How do I verify the results from this guide?

Use the free calculators on Steel Calculator to run each check independently with your specific inputs. Cross-check against hand calculations using the referenced code clauses. A licensed Professional Engineer must review and stamp all final designs.

Beam Design Workflow | Steel Calculator

------------------------------ | ------------------------------------------- | --------------------------------------------- | --------------------------------------- | -------------------------------- | | Flexure phi | 0.90 | 0.90 | gamma_M1 = 1.00 | 0.90 | | Shear phi | 1.00 (most rolled) | 0.90 | gamma_M0 = 1.00 | 0.90 | | LTB approach | Lp/Lr transition, Cb modifier | alpha_m moment modifier, Le effective length | chi_LT reduction factor, LTB curves a-d | omega_2 equivalent moment factor | | Section classification | Compact / Non-compact / Slender | Compact / Non-compact / Slender (Table 5.2) | Class 1 / 2 / 3 / 4 | Class 1 / 2 / 3 / 4 | | Moment capacity (compact, braced) | phi Mn = phi Fy Zx | phi Mn = phi fy Zx | Mc,Rd = Wpl fy / gamma_M0 | Mr = phi Fy Zx | | Deflection limit (floor, live) | L/360 (AISC DG3) | L/250 (AS 1170.0 App C) | L/250 total, L/300 variable (EN 1990) | L/360 (NBC) | | Cb / alpha_m factor | Cb = 12.5Mmax / (2.5Mmax + 3MA + 4MB + 3MC) | alpha_m from Table 5.6.1 or rational analysis | C1 from Table B.3 (EN 1993) | omega_2 from Cl. 13.6 |

Stage 1 — Define the loading

Identify all load cases: dead, live, wind, seismic, construction, and any special loads.
Determine whether loads are applied as point loads, distributed loads, or a combination.
Confirm which load combination standard applies (e.g., ASCE 7, AS/NZS 1170, EN 1990).
Record whether the inputs to the calculator are factored or unfactored — mixing them is the most common beam calculation error.

Stage 2 — Analyse for actions

Confirm support conditions match the analysis model (simple vs fixed vs continuous).
Keep a clean separation between analysis actions (from beam calculator) and member checks (capacity calculator).
Track which loads are service vs factored and avoid mixing them in the same calculation step.

Stage 3 — Select a trial section

Record section properties source (database vs supplier catalog) and axis orientation.
Verify that the section database matches the region and standard you are working with (e.g., W shapes for AISC, UB/UC for AS, IPE/HEA for EN).
Note whether the section is compact, non-compact, or slender — this affects the capacity calculation method.

Stage 4 — Check strength limit states

Flexural capacity: check both yielding and lateral-torsional buckling.
Shear capacity: check web shear (and web crippling/buckling at concentrated load points if applicable).
Record unbraced length and restraint assumptions for stability screening — these have a large effect on capacity.

Stage 5 — Check serviceability

Document both strength and serviceability results, even if one clearly governs.
Identify the deflection limit source (code, project specification, or client requirement).
Confirm which load combination applies to deflection (typically service-level, not factored).
See Deflection limits explained for more detail on serviceability assumptions.

Documentation

Record the governing standard and edition.
Record all input values with units, the trial section, and the controlling limit state with its utilization ratio.
Archive the calculation so another engineer can reproduce it.

Frequently Asked Questions

What is the most common beam design mistake? Mixing factored and unfactored loads. If you enter factored loads into a calculator that then applies its own load factors, the beam is checked against demands that are too high (overly conservative) or the calculator may not apply factors at all (unconservative if you entered service loads expecting factors to be applied).

Should I check deflection even if strength governs? Yes. Deflection limits are serviceability requirements and must be satisfied independently of strength. A beam can pass all strength checks and still violate a deflection limit.

How do I handle lateral-torsional buckling? The unbraced length (distance between lateral restraint points) is the key input. If the beam is continuously braced (e.g., by a concrete slab), LTB does not govern. If discrete bracing exists, you must determine the unbraced length for each segment.

Does the calculator handle continuous beams? The beam analysis tools handle simply-supported and basic configurations. Multi-span continuous beams require a separate analysis to determine the moment and shear diagrams, which can then be used as inputs to the capacity checker.

Is this guide engineering advice? No. It is an educational workflow description to help organize beam design calculations. Project criteria and compliance decisions are defined by the governing standard and the engineer of record.

What unbraced length triggers lateral-torsional buckling for a W18x35 beam per AISC 360? Per AISC 360-22 Table 1-1 for W18x35: Lp (plastic moment limit) ÃÂ¢ÃÂÃÂ 4.31 ft and Lr (elastic LTB limit) ÃÂ¢ÃÂÃÂ 14.0 ft. Below Lp, the full plastic moment Mp governs. Between Lp and Lr, moment capacity reduces linearly. Above Lr, elastic LTB governs and capacity falls rapidly. For a simply supported beam with the top flange continuously braced by a concrete slab, Lb = 0 and LTB does not apply. For an unbraced steel roof beam with Lb = 20 ft, elastic LTB would reduce the available moment significantly below Mp.

What L/360 limit means numerically for a 30-foot floor beam, and what section is typically needed? L/360 = 30 ÃÂÃÂ 12 / 360 = 1.0 inch maximum live-load deflection. For a simply supported beam under a uniform live load of 50 psf on a 10-foot tributary width (500 lb/ft = 0.5 k/ft), the required moment of inertia is I_req = 5wL^4 / (384EÃÂÃÂ) = 5 ÃÂÃÂ 0.5 ÃÂÃÂ 30^4 ÃÂÃÂ 1728 / (384 ÃÂÃÂ 29,000,000 ÃÂÃÂ 1.0) ÃÂ¢ÃÂÃÂ 467 inÃÂ¢ÃÂÃÂ´. From AISC tables, a W18x35 (Ix = 510 inÃÂ¢ÃÂÃÂ´) or W16x40 (Ix = 518 inÃÂ¢ÃÂÃÂ´) would satisfy this limit. Strength (moment) must be checked separately.

Run This Calculation

ÃÂ¢ÃÂÃÂ Beam Capacity Calculator — moment, shear, and deflection per AISC 360, AS 4100, EN 1993 with full derivation output.

ÃÂ¢ÃÂÃÂ Beam Span Tool — shortlist W-shapes for span and load, with deflection limit screening.

ÃÂ¢ÃÂÃÂ Composite Beam Calculator — composite W-shape with concrete deck per AISC 360 Chapter I.

Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Any calculations, outputs, examples, and workflows discussed here are simplified descriptions intended to support understanding and preliminary estimation.

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.