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# Design a Steel Beam to NZS 3404.1:1997 (Amdt 2)
> Design steel beams to NZS 3404.1:1997 (Amdt 2) with multiple supports and loads. Checks compactness, LTB, shear, bearing and deflection.
New ZealandNZS 3404.1:1997 (Amdt 2)
Beam reactions link to the columns and footings below, so load changes propagate downstream automatically. Design steel beams to NZS 3404.1:1997 (Amdt 2) with multiple supports and loads. Checks cover section compactness, lateral torsional buckling, shear and bearing capacity, and short-term, long-term, and imposed-load deflections.
The Calcs.com steel beam calculator enables the fast design and analysis of a steel beam with multiple supports and loads. Engineers can quickly and easily model any type of steel beam, including steel floor and roof beams with a handy range of presets that reduce repetitive data entry and improve accuracy. Loads can be dynamically linked between structural elements, so beams, columns, and connections can easily be linked and checked for adequacy.
## Method & scope
| Property | Detail |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Design standards | NZS 3404.1:1997 (Amdt 2) |
| Regions | Australia & New Zealand |
| What it checks | Structural model, Load combinations (NZS 1170), Section compactness (Clause 5.1 and 5.2), Design moment capacity (Clause 5.1 to 5.3), Shear capacity (Clause 5.11), Bearing capacity (Clause 5.13), Deflection checks (Clause 2.3), Section properties |
#### Calculation method
##### Structural model
The calculator models the steel beam using a finite element method (FEM) engine. Supports are positioned at user-defined locations and can be pins or rollers. The solver produces moment, shear, deflection, and reaction diagrams for every load case and combination.
##### Load combinations (NZS 1170)
Loads are entered by type: permanent (G), imposed (Q), wind (W), and earthquake (E). The character of the imposed load (office, residential, storage, etc.) affects the combination factors psi. The calculator generates and evaluates all governing NZS strength and serviceability load cases, selecting the worst case for each check.
##### Section compactness (Clause 5.1 and 5.2)
Sections are classified by comparing flange and web element slenderness ratios to the yield and plastic limits from NZS 3404. Compactness classification (compact, non-compact, or slender) in bending about each axis determines the effective section modulus Z\_e used in capacity calculations.
##### Design moment capacity (Clause 5.1 to 5.3)
**Section moment capacity (phiM\_s):** computed from Z\_e and yield stress, factored by phi.
**Member moment capacity (phiM\_bx):** accounts for lateral torsional buckling using:
* **alpha\_m:** moment modification factor derived from the bending moment diagram at quarter-points (M2, M3, M4)
* **alpha\_s:** slenderness reduction factor, a function of the reference elastic buckling moment M\_oa and the section moment capacity
* Restraint classification per span (fully, partially, or laterally restrained)
**Utilization:** **moment utilization** = M\*x / phiM\_sx ≤ 1.0
##### Shear capacity (Clause 5.11)
The nominal shear yield capacity V\_w and shear buckling capacity V\_b are computed from web area A\_w and the shear buckling coefficient alpha\_v. The lesser governs. An additional check on the ratio of maximum to average shear stress (f\_vm / f\_va) is performed for non-uniform shear distributions.
**Shear-moment interaction** is checked where both V\* and M\* are significant at a cross-section.
##### Bearing capacity (Clause 5.13)
At each support, the bearing yield capacity and bearing buckling capacity are computed. The member slenderness reduction factor alpha\_c accounts for web buckling under concentrated bearing. An additional bending-bearing interaction check is performed where required.
##### Deflection checks (Clause 2.3)
Three deflection types are checked against user-defined span/n limits:
1. **Short-term serviceability deflection**, under short-term service loads
2. **Long-term serviceability deflection**, including creep and shrinkage effects
3. **Imposed load deflection**, live and imposed loads only
The governing deflection per span is extracted from the FEM solution and compared to the applicable limit. An optional absolute deflection limit (mm) can also be set.
##### Section properties
Properties (I\_11, I\_22, Z\_11, S\_11, S\_22, J, I\_w, A\_g, A\_w, alpha) are read from the built-in NZ/AU steel section database, including UB, UC, PFC, EA, UA, RHS, SHS, and CHS sections. The angle of the major principal axis and the centroid location are used to resolve loads for asymmetric sections.
##### Load linking
Support reactions are exported as linked outputs. Column and footing calculations placed downstream automatically receive the updated reactions when beam inputs change.
## How to use it
Open it from **Run calc** in the About this calculator panel above.
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See [Checks, References, Conditions and Assumptions](/docs/running-calculations/checking-results/checks-references-conditions-assumptions).
Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export).
## Common questions
The calculator designs steel beams to NZS 3404.1:1997 (Amdt 2) using the limit states design method. Load combinations follow NZS 1170.0 and NZS 1170.1 as applicable. Both strength and serviceability limit states are checked.
Key inputs include the steel section and steel type, total beam length, lateral restraint type and maximum spacing at the critical flange, support positions, distributed and point loads by load type (G, Q, W, E), height of load application relative to the shear center, and deflection limit criteria per span.
The calculator produces: design moment demand M*x vs. design member moment capacity phiM\_sx (including lateral torsional buckling via alpha\_m and alpha\_s), design shear demand V* vs. capacity phiV\_vn, bearing demand R\* vs. capacity phiR\_b at each support, shear-moment interaction, bending-bearing interaction, and short-term, long-term, and imposed-load deflection ratios.
The calculator classifies each span's end restraints using the NZS 3404 segment classification table. It then computes the moment modification factor alpha\_m from the bending moment distribution and the slenderness reduction factor alpha\_s from the reference buckling moment. The member moment capacity accounts for both cross-section compactness and LTB.
Yes. For sections loaded at an angle to the principal axes (such as equal and unequal angles), the calculator resolves loads into major and minor axis components and checks biaxial moment utilization.
Yes, beam reactions link directly to connected column and footing calculations. When inputs change, all downstream calcs update automatically.
## Next steps
Design steel beams to AS 4100:2020 with multiple supports and loads. Floor- and roof-beam presets cut repetitive entry.
Complete list of Calcs.com design calculators available for Australian and New Zealand projects (AS 3600, AS 4100, AS 1720, AS/NZS 1170, and related standards).
Design cold-formed steel beams to AS/NZS 4600:2018 using the Direct Strength Method, with a built-in database of Australian CFS sections.
Analyze simple and continuous beams under AS/NZS 1170.0:2002 (Amdt 5) load combinations, with governing demands identified by load case.
