đź“„ Stability & Fire Boundary - Sway Stability, Snap Through and Fire Boundary Design Checks
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Stability & Fire Boundary
Sway Stability, Snap Through and Fire Boundary Design Checks

The Sway Stability, Snap Through and Fire Boundary Design checks are displayed using the Stability & Fire Boundary button in the MasterPort side toolbar.

To apply Sway Stability, Snap Through and Fire Boundary design checks:-

You can assign up to 5 checks for each design check, and have the option to assign a brief title.

The first three input parameters are similar in all 3 design checks

  • Column: Click on the Column cell in the input grid then from the frame geometry area select the column. The member number will be placed in the input cell, and the cursor will move to the next row, ie, Rafter 1 input cell. 
  • Rafter 1: Select the first rafter member
  • Rafter 2: Select the second rafter member

Complete the remaining input data for each check.

Sway Stability Check
SCI P252

This is a quick, code-style screening check on a portal frame. 

See SCI P252 Section 6 – In-plane frame stability → 6.2 Sway check method → “Formula Method” and Section 6.2.2 – Sway-check method for lateral load cases

  • No. of Bays: Number of portal bays.
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The Sway Stability and Snap Through checks are quick, code-style screening checks on a portal frame.

Read more below.

Snap Through Check
SCI P252

This is a quick, code-style screening check on a portal frame. 

It is recommended to utilise the various Analysis options (such as the Elastic Critical Load Factor λcr & P-Delta) to quantify actual global stability effects in your Portal frame .

SCI P252 - the “formula method” checks in the In-plane frame stability section, specifically the snap-through stability subsection.

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The Sway Stability and Snap Through checks are quick, code-style screening checks on a portal frame.

The depend on a Idealised portal mechanism (e.g. no props).

The sway stability check and the snap through check are generally not recommended for modern portal frame design. Both checks are considered legacy things and represent an older, historic way of checking structural stability.

Instead of using these legacy checks, modern design codes address frame stability through the elastic critical load factor (αcrit​). By assessing the elastic critical load factor, you can determine whether the frame is sway-sensitive and if a P-Delta analysis is required to account for second-order effects. The modern buckling analysis methodology effectively captures the modes of failure addressed by snap through type checks.

Fire Boundary Check
SCI P313

MasterSeries Fire Boundary Check is implementing SCI P313’s formula method (with K-factor, geometry coefficients A/B/C, residual moment and VR/HR/OTM checks).

  • Roof load kN/m^2: Reduced Roof Dead Load at Collapse
  • Wall Load kN/m^2: Reduced Wall Dead Load at Collapse

Additional Fire Boundary Checks

The fire boundary checks will also carry though to 

  • Steel Connections Design module to create a base plate design check for the associated bay.
  • Concrete Pad Foundation Design â€“ The same load case transfers to the Pad/Column Base module, ensuring axial load, shear and punching checks are re-run with the reduced wall/roof dead loads appropriate to a fire scenario.

Output

The calcs will show if the particular check is passing of failing.

Printing and Exporting of these 3 design checks is carried out from within the general checks tabs at the bottom of the screen, and not in the main print manager.

  •   Print/Export the current design brief, i.e., only the active number of the active design check.
  •   Print/Export all briefs numbers (which contain data) for all 3 design checks.


Nodal Displacements

In MasterPort, the nodal displacements check is located along with the four general checks as outlined above. Displacement checks are automatically generated for sway stability, and horizontal eaves displacement on the eaves nodes, as well as vertical displacements on the apex nodes, as shown below.

Additional check nodes can be added along with the relevant load cases, displacement directions and limits if applicable. Up to 9 lines of checks can be included.

As with the general checks, printing and exporting is controlled from the nodal displacements tab and not the general print manager.

  Print/export the nodal displacement checks as they appear in the grid.