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Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?

Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?

Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?

Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?

Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?

Per the attached figure, when calculating snow drift, I typically assume the wind blows in a direction diagonal to the main building footprint giving an upwind fetch distance of the square root sum of the squares of the building width and length.  I have seen other engineers take the upwind fetch distance as the perpendicular distance from the edge of the building to the parapet (B in the attached sketch).  Typically, the first approach which may be slightly conservative still gives reasonable numbers.  However, when the building is very long compared with the width (as might be the case for an industrial building), using the square root sum of the squares gives an extremely large drift compared with only using the perpendicular distance.  Is there any justification in ASCE 7 for using the perpendicular distance?