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# Design a Concrete Member (Design Only) to AS 3600:2018 (R2021)
> Design concrete members to AS 3600:2018 from analysis forces you already have, such as 3D model results. Fast capacity design and reinforcement optimization.
AustraliaAS 3600:2018 (R2021)
Design concrete members to AS 3600:2018 from analysis forces you already have, such as results taken from a 3D structural model. Capacity design for members whose demand comes from external analysis.
The Concrete Member Design Only calculator to AS 3600:2018, is perfect for the fast capacity design of concrete members where engineers already have analysis results available (for example, when forces are being taken from a 3D analysis model of a concrete structure). By enabling easy input of analysis forces on the member, the concrete member calculator enables the fast and optimized design of concrete reinforcement.
## Method & scope
| Property | Detail |
| ------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Design standards | AS 3600:2018 (R2021) |
| Regions | Australia & New Zealand |
| Who it's for | AU structural engineers doing fast capacity checks on concrete beams and columns where moment and shear demands are already known — preliminary design validation, retrofit/upgrade assessments, and custom sections with unique geometries or reinforcement configurations. |
| What it helps with | Input moment and shear demands directly and get AS 3600:2018-compliant capacities plus utilization summaries without building a full structural model. Streamlines reinforcement optimization when forces come from a 3D analysis model, and handles bespoke member designs the standard beam/column calculators don't cover. Fully released out of beta in Dec 2024. |
| Presets | Manual Input, (BETA) Link to Analysis Module |
| What it checks | Axial capacity, Bending and axial interaction, Biaxial bending, Shear, Tension, Deflection: creep and shrinkage |
#### What it calculates
Australian structural engineers running capacity checks on concrete beams and columns when the moment and shear demands are already known, from a 3D analysis model or hand calculations. Suits preliminary design validation, retrofit and upgrade assessments, and custom sections the standard beam and column calculators do not cover.
Input moment, shear, and axial demands directly and get AS 3600:2018 capacities plus utilization summaries without building a full structural model. Streamlines reinforcement optimization when forces come from a 3D analysis model, and handles bespoke members the standard beam and column calculators do not cover.
#### Calculation method
The calculator performs a capacity design of a reinforced concrete member to AS 3600:2018 from design actions the engineer supplies directly. It suits members whose forces come from a separate analysis, such as a 3D structural model, and reports each action as a demand-versus-capacity check with the governing clause shown.
##### Axial capacity
For members carrying axial load, the ultimate squash load is found from the concrete and reinforcement areas using the uniform compressive stress block (Cl 10.3, 10.6.2.2). Slenderness is then addressed through the axial buckling capacity (Cl 10.4): the calculator classifies the column as braced or sway about each axis, computes the buckling load, and applies a moment magnifier that amplifies the design moment for second-order effects.
##### Bending and axial interaction
Moment capacity is evaluated with the axial demand acting simultaneously. For each axis the calculator constructs the interaction curve from key points: the decompression point (Cl 10.6.2.3), the balanced failure point (Cl 10.6.2.5), the pure bending capacity (Cl 8.1), and the general combined axial-and-moment condition (Cl 10.6.2.4-5). At each point it resolves the neutral axis location and parameter, the depth of the concrete compressive stress block, the concrete compression force, and the corresponding capacity reduction factor, giving the factored ultimate moment capacity at the applied axial load.
##### Biaxial bending
When bending acts about both axes at once, the biaxial moment and axial interaction is checked with the power-law rule of Cl 10.6.4. The power coefficient is derived from the axial utilization, and the combined utilization about the two axes must be 1.0 or less.
##### Shear
Shear about each axis is checked with the sectional design method (Cl 8.2). The calculator computes the effective shear depth and breadth, the angle of the compression strut, the web crushing limit, the concrete shear strength contribution, and the reinforcement contribution from the fitments, then reports the factored shear capacity against the shear demand. The simplified concrete shear method is valid when the concrete strength is 65 MPa or less with no prestressing, tension, or torsion.
##### Tension
For members in net axial tension the ultimate tensile load is taken from the reinforcement yield capacity with the relevant capacity factor, and checked against the tension demand.
##### Deflection: creep and shrinkage
Serviceability uses the simplified deflection method (Cl 8.5.3). The calculator derives the drying, autogenous, and total shrinkage strains (Cl 3.1.7) and the creep factor (Cl 3.1.8) from the concrete age at loading, member geometry, and climate environment. Cracked and uncracked second moments of area are combined into an effective second moment of area, and short- and long-term deflections are compared against the entered deflection and extension limits.
##### Assumptions
Torsion, prestressing, and post-tensioning are not considered, and detailing requirements (covered by Cl 4, 5, and 8.3, among others) are checked separately. For columns, the worst-case compression and moment actions are not necessarily from the same load combination, transmission of axial force through floor systems (Cl 10.8) is not checked, and columns in net tension are excluded. All utilization ratios must be 1.0 or less for the design to pass.
## How to use it
Open it from **Run calc** in the About this calculator panel above. To start from a typical setup, choose one of the presets listed there.
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).
## Available presets
Each preset opens the calculator with a typical setup already entered.
| Preset | Open in Calcs.com |
| ------------------------------------------------------- | ------------------------------------------------------------------------------------------ |
| Manual Input | [Run with preset](https://app.calcs.com/new/sheet/AUConcreteMember?presetCode=manualInput) |
| (BETA) Link to Analysis Module | [Run with preset](https://app.calcs.com/new/sheet/AUConcreteMember?presetCode=elementLink) |
## Common questions
AS 3600:2018, the Australian concrete structures standard. Column actions use the axial squash and buckling provisions (Cl 10.3, 10.4, 10.6) and the biaxial interaction rule (Cl 10.6.4); beam actions use the flexural provisions (Cl 8.1) and the sectional shear design method (Cl 8.2). Deflection uses the simplified method (Cl 8.5.3) with creep and shrinkage from Cl 3.1.7 and 3.1.8.
Member type (beam or column), total member length, and cross-section depth and breadth. Concrete strength and type, end restraint condition or a custom effective length factor. Longitudinal reinforcement (corner and additional bars per side, type, and cover to fitments) and fitment type, spacing, and leg arrangement. Design loads are entered directly: axial compression or tension, bending moment about the X and Y axes, shear about the X and Y axes, and initial deflection or extension where relevant.
For columns: axial squash capacity, axial buckling capacity, moment capacity about each axis considering the axial demand, biaxial moment and axial interaction, and tension capacity. For beams: positive and negative moment capacity, shear capacity, and short- and long-term deflection limits. Shear about each axis is also checked. Every action is reported as demand versus capacity with the governing AS 3600:2018 clause.
Yes. For each axis the calculator builds the interaction curve from the decompression point (Cl 10.6.2.3), the balanced failure point (Cl 10.6.2.5), the pure bending capacity (Cl 8.1), and the combined axial-and-moment condition (Cl 10.6.2.4-5). The biaxial case is then checked with the power-law interaction of Cl 10.6.4. Members in net tension are not considered.
The Concrete Member (Design Only) calculator takes the design actions (axial force, moment, and shear) directly rather than deriving them from spans and applied loads. That makes it suited to capacity design where the forces already exist, such as results from a 3D analysis model, and to bespoke members with geometry or reinforcement the dedicated beam and column calculators do not cover.
Yes. The member design actions can be linked directly from a structural analysis result in the same Calcs.com project, so the capacity checks update automatically when the analysis forces change. This keeps reinforcement optimization in step with the model without manually re-entering axial, moment, and shear demands.
## Next steps
Design rectangular concrete beams to AS 3600:2018 (Amdt 2) with unlimited spans. Checks flexure, shear, and short- and long-term deflection.
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 rectangular and circular reinforced concrete columns to AS 3600:2018 (Amdt 2), with P-M interaction, biaxial bending, slenderness and shear.
Design reinforced concrete walls to AS 3600:2018 (Amdt 2), including fire resistance and load combinations.
Design one-way reinforced concrete slabs to AS 3600:2018 (Amdt 2) with live FEA. Checks moment capacity, shear, and short- and long-term deflection.
Changes in AS3600:2018 Amendment 2 (Concrete)
