StruSheets
How to Calculate Wind Coefficient in StruSheets
Use the StruSheets Wind Coefficient Calculator the same way as the original roof and wall effective-area workbook: span, tributary widths, enclosure and qh.
The Wind Coefficient Calculator is the browser version of the office Wind Co-efficient spreadsheet. It is not a black-box wind-load engine. It reconstructs the effective-area curves that PEB engineers already use for roof and wall components.
What you are calculating
Component and cladding coefficients depend on effective wind area. The workbook — and StruSheets — take member span L and the two adjacent tributary widths A and B, then use:
- Effective width = MAX((A+B)/2, L/3)
- Effective area = span × governing width, converted to ft²
- A piecewise log curve for roof or wall, enclosed or partially enclosed
- Pressure = coefficient × qh
Inputs that matter
- Choose Roof or Wall. The breakpoints change: 10 and 100 ft² on roofs, 10 and 500 ft² on walls.
- Set Enclosed or Partially Enclosed. That shifts GCpi and the curve intercepts.
- Enter span and left/right tributary widths in metres, the same yellow cells as the spreadsheet.
- Enter qh in kPa from your MWFRS or velocity-pressure calculation.
How to read the report
The A4 page lists zone coefficients and the matching pressures. The governing value is the largest absolute coefficient. Use that for cladding, purlin or girt checks, not as a frame MWFRS load.
Common mistakes
- Do not enter mm for span or tributary width.
- Do not mix roof curves with wall members.
- Confirm enclosure classification from the Building Condition Check before picking Partially Enclosed.
- qh must be in kPa, not psf.
Related StruSheets
This article provides general educational information. Project-specific structural design, calculations and drawings should be reviewed by appropriately qualified engineering professionals and checked against applicable project requirements and standards. StruTools does not replace engineering judgement or professional design review.