Australian / New Zealand Standard 4600 for Cold-Formed Steel Structures, 2018 Edition
The AS/NZS 4600:2018 module checks cold-formed steel members with the Direct Strength Method. It runs in SkyCiv Structural 3D and supports custom restraints along each member.
For the 2005 edition, see AS4600 Member Design.
With this module you can:
- Run design checks to AS/NZS 4600:2018 with the Direct Strength Method, including:
- Member pre-qualification
- Axial tension
- Axial compression: section capacity, and member capacity for global, local and distortional buckling
- Bending about both axes: section capacity, and member capacity for lateral-torsional, local and distortional buckling
- Shear along both axes
- Combined bending and shear
- Combined compression and bending
- Combined tension and bending
- Design channels, Z sections, hat sections, back-to-back channels and lipped channel boxes, prismatic or non-prismatic
- Define custom restraints and pseudo-restraints along each member
- Export detailed step-by-step PDF reports
- Run the SkyCiv Designer (Run Designer) to find the most efficient section
Current version support
Sections
- Channel
- Lipped Channel
- Lipped Channel single
- Z Section
- Lipped Z
- Hat Section
- Back-to-back Channels
- Back-to-back Lipped Channels
- Lipped Channel Box
Back-to-back lipped channels and lipped channel boxes are supported only by this code. Sections can be prismatic or non-prismatic, and the material must be steel. Sections must not come from the Australian/Steel (250 Grade), Australian/Steel (300 Grade), Australian/Steel (DuraGal) or American/AISI databases.
To see this list in the software, open the log and click View supported sections.
Software
- SkyCiv Structural 3D
AS/NZS 4600-2018 is also listed in the Design Code dropdown of SkyCiv Beam. This page describes the module in SkyCiv Structural 3D.
Note
Units must be in Metric to use this design module. In the Model, open Settings (top bar) > Units and set the unit system to Metric.
Opening the module
- Solve the model.
- Click Design in the top bar.
- In Select a Design Module, choose Cold-Formed Steel Member.
- In Which design code would you like to start?, pick AS/NZS 4600-2018, then click Start.
If a design module is already open, use Change Module in the Design menu to switch codes.
The design panel opens on the left, with the 3D model on the right. The header shows the code, plus Request Feature and Run Designer. On the right of the tab bar are three buttons:
- the settings (gear) button, which opens Member Design Settings
- the log button, which opens the Member Design Log
- Check, which runs the design check
When the module starts, an alert may tell you that there are important messages. They are shown in the Member Design Log, for example "6 members were loaded with default values", or members that were not imported because their section or material isn’t supported. The log has a View supported sections link.
The tabs are Details, Factors, Materials, Sections, Members, Restraints, Loads and Results.
Member Design Settings
Click the gear button to open Member Design Settings. It has one option:
- Checks based on geometric axes instead of principal axes: unchecked by default. It affects the capacity of sections that are not symmetric about both axes, such as Z sections.
As the dialog notes, engineering guidance should be used when you change these settings. Click Save to apply.
Details
On the Details tab you can enter the project details. You don’t have to fill them in, but anything you enter is shown in the Project Details table of your reports. Project Units shows Metric and can’t be changed here.
Factors
The Factors tab shows the capacity reduction factors:
| Factor | Description | Default |
|---|---|---|
| ΦC | Compression | 0.85 |
| ΦB | Bending | 0.9 |
| ΦV | Shear | 0.9 |
| ΦT | Tension | 0.9 |
If a member is not pre-qualified (Clause 1.6.3(c)(i)), ΦC, ΦB and ΦV are reduced to 0.8. The factors used for each member are listed in its report under Strength Limit State Factors, with their clause references.
Materials
The Materials tab lists the materials used by the designed members, with their Yield Strength and Ultimate Strength. The table is filled in from the model and can’t be modified here. To change a material, go back to the Model.
Sections
The Sections tab lists the sections used by the designed members. The section data comes from the model and can’t be modified here.
- Design: tick the box to design the members that use this section. The icon in the column header toggles all rows.
- Section ID, Section, Shape, Material ID and Material: taken from the model.
- DSM: click View to see the DSM factors of the section.
The DSM Factors for Section n dialog shows a sketch of the section with its axes, and the elastic buckling stresses (in MPa) used by the Direct Strength Method:
| Symbol | Buckling stress |
|---|---|
| fo,l,c | Local buckling, compression |
| fo,d,c | Distortional buckling, compression |
| fo,l,bx | Local buckling, bending about x |
| fo,d,bx | Distortional buckling, bending about x |
| fo,l,by,- and fo,l,by,+ | Local buckling, bending about y (negative and positive) |
| fo,d,by,- and fo,d,by,+ | Distortional buckling, bending about y (negative and positive) |
Any factor that is not provided has its check skipped. For a section that is symmetric about an axis, the positive and negative factors about that axis are not needed. The values can’t be edited here: to change them, go to the Section Builder and launch the Cold Formed Steel Design module.
Members
The Members tab lists the design members. Each design member is made up of one or more model members.
- Expand Table Width: widens the table.
- Split Selected and Join Selected: split the selected design members, or join them into one design member.
| Column | Description |
|---|---|
| Select | Ticks the row, for example to split or join members |
| Design | Tick to include the member in the design check, untick to leave it out |
| Design Member ID | The ID of the design member |
| Member IDs | The model member(s) that make up the design member |
| Section IDs | The section(s) of the design member |
| L (m) | The length of the design member |
| Restraint ID | The restraint set used by the member. Click it to open that restraint in the Restraints tab |
Design Member ID, Member IDs, Section IDs and L (m) come from the model and can’t be changed here. Effective lengths and K factors are not entered on this tab: they come from the Restraints tab.
Restraints
AS/NZS 4600:2018 supports custom restraints, so you can add your own restraints to be used in the calculations. For a full description, see our documentation on member restraints.
- Auto Group: gives similar members the same restraint ID.
- Restraint ID: selects the restraint ID to view or edit. Use the down and up arrows to go to the next or previous ID.
- Assign to Member(s): assigns the current restraint ID to members.
- Duplicate: copies the current restraint ID to a new ID.
The restraint table is filled in from the model supports and connections. For example, a member supported at both ends gets a row at each end.
| Column | Description |
|---|---|
| Select | Ticks the row, for example to apply a standard restraint to it |
| Position | Distance of the restraint from the start of the member |
| Major Compression | 2-key restraint code (F or R) for major-axis flexural buckling |
| Kz | Effective length factor for the major axis (auto by default) |
| Minor Compression | 2-key restraint code (F or R) for minor-axis flexural buckling |
| Ky | Effective length factor for the minor axis (auto by default) |
| Lateral-Torsional | 4-key restraint code (F, R or S) for lateral-torsional buckling |
| Global Buckling Bracing | Unbraced, Top, Bottom or Both. If the lateral-torsional restraint fully braces a flange, the global buckling check is skipped for the cases that the bracing covers. Hover over the ℹ icon for details |
| Delete | Deletes the restraint row |
To add pseudo-restraints (restraints that are not modelled), enter the spacings in Add pseudo-restraints by spacing(s) and click Add. You can enter a comma separated list (for example 1.5,1.5,1.5), use the multiply operator (4*1.5), or use the < operator to fit as many restraints as possible. Click Delete next to Add to remove all the pseudo-restraints.
Pseudo-restraints are added as released (RR and RRRR), so they have no effect until you change their codes. In the example below, 4*1.5 adds rows at 1.5, 3 and 4.5 m on a 6 m member, and their Lateral-Torsional code is changed to FFFR.
Below the table are sub-tabs, each with an A (automatic) badge by default:
- Tension: with Default values on, the defaults are used. Switch it off to enter your own:
- kt: correction factor for the distribution of forces in a tension member. The default assumes a non-uniform force distribution, per AS/NZS 4600:2018 Clause 3.2.3.2.
- An factor: factor that reduces the gross area to the net area. The default is 0.85, which assumes a bolted connection.
- Major Compression (Lz, Kz), Minor Compression (Ly, Ky), Twist Compression (Lx, Kx), Major Lateral-torsional (Lb, kLT, Cb) and Minor Lateral-torsional (Lb, kLT): by default, Determine from restraints (as defined in the restraints table) is on. Switch it off to enter your own values for the whole member. Under Standard Restraints, click an icon to apply a standard restraint to the selected rows.
The Restraints section of each member report shows the restraints that were used: the user input (position, restraint codes, kez and key, top and bottom flange restraint, member rotation and global buckling bracing), the major-axis and minor-axis compression segments, the compression twist segments, the effective lateral-torsional restraints and the segments for each load combination.
Loads
The Loads tab lists the load combinations from the model, with their Name and Criteria. Tick Apply for each load combination you want to include. Serviceability combinations are listed and can be ticked, but no serviceability check is performed.
Results
Click Check to run the design check. The Results tab shows:
- Show Design Ratios for: chooses which ratios are shown, for example Governing Result, Failed Members, or a single check.
- GOVERNING: the highest ratio and its member.
- A toolbar to filter (All), sort, copy, show the table and open the report, plus a Summary button for the summary report.
- The Member Design Ratios table, with a Status (Pass or Fail) and a Report icon for each member. Hover over the ℹ icon in a column header to see the clause it refers to.
| Column | Check | Clause |
|---|---|---|
| P | Axial (tension or compression) | 3.2 or 7.2.1 |
| Mx | Bending about x | 7.2.2 |
| My | Bending about y | 7.2.2 |
| Vy | Shear along y | 7.2.3 |
| Vx | Shear along x | 7.2.3 |
| CSBx | Combined shear and bending, about x | 7.2.3 |
| CSBy | Combined shear and bending, about y | 7.2.3 |
| CCB | Combined compression and bending | 7.2.4 |
| CTBm | Combined tension and bending, member capacity | 7.2.5(1) |
| CTBs | Combined tension and bending, section capacity | 7.2.5(2) |
In the 3D view, each member is coloured Fail, Warning or Pass and labelled with its governing ratio.
Checks performed
| Check | AS/NZS 4600:2018 reference |
|---|---|
| Member pre-qualification (sets Φ) | Clause 1.6.3 |
| Axial tension, section capacity | Section 3.2 |
| Axial compression, section capacity | Section 7.2.1.3 |
| Axial compression, member capacity (global, local and distortional buckling) | Section 7.2.1 |
| Bending about x and y, section capacity | Section 7.2.2.3.2 |
| Bending about x and y, member capacity (lateral-torsional, local and distortional buckling), including positive and negative bending about y for singly symmetric sections | Section 7.2.2.1 |
| Shear along y (web) and along x (flange) | Section 7.2.3 |
| Combined bending and shear, about both axes | Eq. 7.2.3(9) |
| Combined axial compression and bending | Eq. 7.2.4 |
| Combined axial tension and section bending capacity | Eq. 7.2.5(2) |
| Combined axial tension and member bending capacity | Eq. 7.2.5(1) |
The module does not check slenderness limits, deflection (serviceability), web crippling or torsion.
Reports
Click the report icon in a member’s Report column to open its design report. It opens in a Design Report for Member #n dialog with Close, Open in New Tab, Download HTML and Download PDF buttons. The report is titled "AS/NZS 4600-2018 – Direct Strength Method", and contains:
- Project Details
- Utility: every check with its reference, symbol, description, ratio and status
- Sections: the dimensions and properties of the section
- Ultimate Limit States: Member Pre-Qualification, Strength Limit State Factors, Member Internal Actions, Member and Restraints, followed by each check step by step
Click Summary on the Results tab to open the Summary Report. It lists the project details (including the design code), the strength load combinations with their factors, and the results for all members.
