Sunday, 8 June 2014

Sample Spreadsheet Calculations for Portal Frame Shed

Example spreadsheet calculations for determination of wind loads on a building with  a doubly pitched roof to the criteria of AS1170.2. Once reference wind pressure been found, then pressure coefficients on the external surfaces are found for directions theta=0 (transverse wind load) and theta=90 (longitudinal wind load). The moments in an assumed single span doubly pitched portal frame (or gable frame), are then calculated using Kleinlogel rigid frame formula: the frame is assumed to have fixed bases (eg. moment connections). Then based solely on sectional strength a minimum size steel section is selected. This section may not be suitable if cannot provide adequate lateral torsional restraint, and pass the detailed member capacity checks.

These calculations can be carried out using the following spreadsheet:

Additional structural calculations are required to design a full building, this is just the calculations for the action-effects of the primary frame, and the design actions on the building. Ignoring the rigid frame, the spreadsheet simply provides the wind actions for the surfaces of the building which can be used to assess/design other components. Other components would include the following:

  1. Roof X-Bracing and struts
  2. Wall X-Bracing and struts
  3. Roof Purlins (cladding rails)
  4. Wall Girts (cladding rails)
  5. End Wall Mullions


[08/06/2014] : Original
[14/09/2015] : Added some notes.