ASCE 7-16 Update A. Lynn Miller, P.E. Senior Code Compliance Engineer PGT Custom Windows + Doors
ASCE 7-16 Simplified Language for Effective Wind Area (Chapter 26 Commentary): •
Current language in ASCE 7-10: For typical door and window systems supported on three or more sides, the effective wind area is the area of the door or window under consideration. For simple spanning doors (e.g.,horizontal spanning section doors or coiling doors), large specialty constructed doors (e.g., aircraft hangar doors), and specialty constructed glazing systems, the effective wind area of each structural component composing the door or window system should be used in calculating the design wind pressure.
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New simplified language in ASCE 7-16: For windows, doors and other fenestration assemblies, the effective wind area for typical single unit assemblies can be taken as the overall area of the assembly. For assemblies comprised of more than one unit mulled together or for more complex fenestration systems, it is recommended that the fenestration product manufacturer be consulted for guidance on the appropriate effective wind area to use when calculating the design wind pressure for product specification purposes.
ASCE 7-16 Components and Cladding 0.6 Rule Written into Chapter 26 Commentary: •
C&C Rating for Building Envelope Products. Building envelope products that have been tested to air pressure standards (such as ASTM E330, CSA A123.21, or other standards that incorporate a safety factor) are typically rated for an allowable stress design wind pressure (0.6W) rather than a strength design pressure (1.0W) or wind speed. In order to properly select products tested and rated in this manner, the C&C pressures determined from Chapter 30 should be adjusted for the allowable stress design load factor of 0.6W in Section 2.4.1.
ASCE 7-16 Directionality Factor, Kd: Currently, many engineers misinterpret the footnote at the bottom of Table 26.6-1 ASCE 7-10: Since no load combination on fenestration (no dead load), some felt that the 0.85 did not apply and defaulted to 1.0.
ASCE 7-16: The footnote has been removed, thus confirming that 0.85 is the appropriate factor to use for directionality.
ASCE 7-16 ASTM E1886/E1996 Version Update: • E1886 reference updated to 2013 version o Updating to the 2013 version clarifies that ASD design pressures are to be used for cyclic testing • E1996 reference updated to 2014 version o Since this standard now references the ultimate wind speed maps, the wind zone adjustment user note has been removed:
ASCE 7-16 Tornado Commentary: • New provisions have been added to the commentary to provide information and guidance for those designing structures in tornado-prone regions. • Provides enhanced design criteria such as higher wind speeds, partially enclosed internal pressure coefficient, directionality factor of 1.0, more stringent impact requirements for higher EF-rated tornadoes. • Intended to be a non-mandatory informational guide only and is not part of the main body of the standard.
ASCE 7-16 New Roof Pressure Coefficients for Low-rise, Sloped Roofs: • Current coefficients in ASCE 7-10 for low, moderate-sloped roofs are derived from limited research based on 4:12 pitched gable roofs only. Recent research has found that these values are too low. • Current standard has no GCp values for hip roofs with slopes greater than 27 degrees. • New research for ASCE 7-16 includes wind tunnel test models of hip roofs with 4:12, 5:12, 6:12, 7:12, 9:12, and 12:12 pitches. • Significant changes in roof zone configurations and increased GCp coefficients have induced great controversy in the roofing industry.
ASCE 7-16 New Wind Speed Maps for All Risk Categories (Risk Category II Shown Below): • Hurricane-prone regions in SE same as ASCE 7-10, non-hurricane regions of the US have been reduced
ASCE 7-16 Existing Risk Category II Map in ASCE 7-10 (700-year MRI):
ASCE 7-16 New Wind Speed Map for Risk Category IV (3,000-year MRI): •Currently, Risk Categories III and IV are in the same map with a 1,700 MRI
ASCE 7-16 Existing Risk Category IV Map in ASCE 7-10: (1,700-year MRI):
ASCE 7-16 • Current Status of ASCE 7-16 • The standard has been adopted into the 2018 IBC and IRC as the referenced standard for design loads. o New maps have been adopted into IBC but not IRC. This will likely cause a great deal of confusion (similar to the different maps used in the 2012 IRC). o New roof pressure coefficients will likely not be adopted by the IRC. • ASCE 7-16 should be available for purchase sometime in July of 2017
• Questions?
