The Internal birdcage scaffolding module checks tube and fitting birdcage scaffolding, in internal locations not exposed to the wind, for compliance with TG20:21.
The software checks whether the scaffold is TG20:21 compliant, calculates the maximum leg loads for foundation design and, if the scaffold is tied, the maximum tie duty and required tie pattern.
The following sections provide details of the user inputs required, and also explain the outputs provided by the software.
The display panel options are similar to that of the Tied independent scaffolding module, with the following options available:
A map is provided to search for the site address. Note that, for an internal birdcage scaffold, a wind calculation is not performed from the site location as is the case for independent scaffolding.
A 3D preview of the birdcage is displayed, which updates as the input options are selected. Holding down the left mouse button will allow you to rotate the view, the mouse scroll wheel can be used to zoom in or out and holding the right mouse button will allow you to pan the view.
2D illustrations of the birdcage are provided in first-angle projection, displaying the front elevation, side elevation and plan view.
A summary report is provided when the calculations are performed, including the 2D elevations, the birdcage loading and dimensions, the calculated leg load and, if applicable tie duty, and the results of the TG20:21 check.
The following options are available for selecting the site location:
| Input | Description |
|---|---|
| Site details | The site address can be selected by searching for an address from the Search bar above the map, or by moving the site marker. This address can be manually overwritten if required, which does not alter the location of the site on the map. |
You can enter the scaffolding dimensions by selecting the Scaffolding tab, this will automatically switch the display from the map to the 3D model. The 3D model updates whenever the inputs are modified.
| Input | Description |
|---|---|
| Load class |
The maximum permitted loading on the scaffold in accordance with TG20:21 Operational Guide section 13.1. One lift may be loaded to the given load class, plus either one lift 50% loaded or, in the case of perimeter boarding, one lift of perimeter boards may be loaded. Changing the load class automatically defaults the maximum bay length and width in accordance with TG20:21, which may then be modified if required. The load class is limited to 1 – 3 for TG20:21 compliant birdcages. |
| Scaffold length |
The length of the scaffold in the direction of the ledgers, limited to 20 m. This should be a multiple of the maximum bay length if you do not want the bay lengths to be averaged. |
| Scaffold width |
The length of the scaffold in the direction of the transoms, limited to 20 m. This should be a multiple of the maximum bay widths if you do not want the bay widths to be averaged. |
| Maximum bay length | The maximum bay length for the scaffold, limited by the load class as in Table 13.2 of the TG20:21 Operational Guide. |
| Maximum bay width | The maximum bay width for the scaffold, limited by the load class as in Table 13.2 of the TG20:21 Operational Guide. |
| First lift height | The maximum height of the first lift, which is limited to 2.5 m in accordance with section 13.1 of the TG20:21 Operational Guide. |
| Lift height | The maximum height of the lifts above the first lift, limited to 2.0 m in accordance with section 13.1 of the TG20:21 Operational Guide. |
| Number of lifts | The total number of scaffold lifts, whether boarded, unboarded or perimeter boarded. |
| Lift boarding |
Specifies how many lifts are boarded and whether perimeter boarding will be provided to access the surrounding walls below the top lift. The available options depend on the number of lifts, with all options available for birdcages with at least three lifts. |
| Number perimeter boards | The width of the perimeter access platforms in scaffold boards. |
| Stabilisation method |
Specifies how the scaffold will be stabilised, as described TG20:21 Operational Guide section 13.1, either:
|
| Foot lift |
Specifies whether the scaffold will have a foot lift, as described in TG20:21 Operational Guide section 13.2. A foot lift is required for a single-lift TG20 compliant internal birdcage. |
| Tube material |
The tube material from which the scaffold will be constructed, in accordance with TG20:21 Operational Guide section 4.1:
The tube material can be identified on delivery with a stamped marking or attached tag stating the steel designation, for example ‘EN 10219 – S 355 JOH’. |
