ANSI SPRI WD-1 2020 pdf free download – Wind Design Standard Practice for Roofing Assemblies.
Verify Roofng System Suitability In order to determine if this adhered membrane roofng system assembly is suitable for use, compare the Factored Tested Load Capacity (L t ) to the calculated feld area (zone 1 ) wind uplift design load. Since L t (-30 psf or -1 .5 kPa) exceeds the design load for zone 1 (-22.1 psf or -1 .1 kPa), the roofng system assembly, as tested, is suitable for use in the feld area of the roof (both zone 1 and zone 1 ’). Perimeter & Corner Layout Evaluation L t (-30 psf, -1 .5 kPa) exceeds the calculated wind uplift design load for the perimeter (-29.1 psf, -1 .4 kPa) area of the roof, but L t is less than the corner area design load (-39.7 psf, -1 .9 kPa). Consequently, the as-tested assembly is suitable for use in the perimeter area but not in the corner area. To determine if rational analysis is acceptable for defning the assembly layout for the corner area, check the requirements of Section 2.5.1 of this document. 1 .
Tested Wind Uplift Load Capacity is greater than the calculated corner area design load X 2. Roofng system assembly utilizes mechanical fasteners for insulation attachment √ Since L t is less than the corner area design load, rational analysis is not permissible for the corner area. An alternate roofng system assembly with an L t greater than the corner area design load will need to be selected for use in the corner area. However, as an option, this alternate roofng system assembly could be used over the entire roof. Ultimate Wind Uplift Design Load Notes The use of ultimate wind uplift design loads (without conversion to allowable design loads) is possible with this document if required by the designer of record. The methodology outlined in Section 2 of this document will still be applicable.
When calculating wind uplift design loads utilizing either ultimate wind speed maps (as contained in ASCE 7-1 6) or using a safety factor of 1 .0 with allowable loads, rational analysis for the perimeter and corner areas for adhered membrane roofng system assemblies will not be possible. The reason is that the 1 .0 safety factor is contained in the Rational Analysis rule: “The Tested Wind Uplift Load Capacity (without consideration of any safety factor) must be greater than or equal to the calculated corner area wind uplift design load”. In this instance multiple assemblies can be used in the feld, perimeter and corner areas (to meet the specifc zone uplift pressures) or one assembly (that meets the corner design load) can used across the entire roof. This “lesson learned” applies only to adhered membrane roofng system assemblies. The Rational Analysis rules are different for mechanically fastened membrane roofng system assemblies.
A building with a futed steel deck has the following calculated allowable design wind uplift loads determined by using the ASCE Standard (pre 7-1 6 edition, therefore no 1 ’ zone). A safety factor of 2.0 is being used along with the allowable design loads for this example.
Calculated design wind uplift loads:
f Field area=-25.6 psf (-1 .2 kPa)
f Perimeter area=-42.9 psf (-2.1 kPa)
f Corner area=-64.6 psf (-3.1 kPa)
Note: The ASCE 7-1 0 and earlier Standards do not include a zone 1 ’ area.ANSI SPRI WD-1 pdf download.