Shear/Braced Wall Panel Design
Proper wall bracing is critical in the design of any home. It is critical not only because it increases life safety and adds to the overall structural quality of a house, but because the code requires it. Current code for wall bracing can be complex, the International Residential Code (IRC) has a number of provisions which must be followed. Wall bracing provides racking resistance against horizontal (lateral) racking loads from wind and earthquakes and prevents the wall studs from distorting in the plane of the wall (racking) in “domino fashion” and, thus, prevents building collapse. Our firm is very familiar with city requirements and can perform complete wall bracing designs as part of our design package. Below are some basic descriptions to help understand the concepts behind the braced wall panel (BWP).
Braced Wall Panel:
• A braced wall panel is a section of a braced wall line that has the ability to resist lateral forces created by winds and seismic eventss.
Braced Wall Line:
• A braced wall line per the International Residential Code (IRC) is an exterior or interior wall line that contains braced wall panels within 12.5 feet of both ends (or 8 feet in Seismic Design Categories D0, D1 or D2), and 25 feet on center throughout the length of the braced wall line. Braced wall lines must occur every 25-35 feet depending upon your Seismic Design Category and wind zone. Braced wall panels are permitted to be offset from the braced wall line up to 4 feet on either side of the braced wall line. An offset greater than 4 feet is treated as an additional braced wall line.
• A prefabricated panel is a manufactured wall panel that is equivalent to a braced wall panel for use in a narrow section of wall. These panels can be used as a substitute for the 8 traditional methods of wall bracing. When calculating the percentage of bracing within a braced wall line, each narrow prefabricated braced wall panel counts as 4 feet of bracing.
• Continuous sheathing is a method of bracing a wall that requires the entire wall line to be covered with wood structural panel sheathing meeting all the provisions set forth in the IRC, which includes special nailing details at corners.