Shear Wall Design

Segmented Shear Wall Design
 
          There are two design methodologies used for shear walls: Segmented Design  and Perforated Design.   The majority of this tutorial concentrates on the traditional segmented shear wall (SSW) design approach.  An introduction to the perforated design approach and its benefits will be presented later in this tutorial.
 
          Segmented Shear Wall Design (SSW) is the traditional design method that has been used for many years.  In the SSW method, walls are divided into segments of full-height sheathing.  These segments are typically separated by openings in the wall such as doors and windows.  The lengths of each full-height sheathing segment (bi) are summed together, resulting in a conservative estimate of the length of the wall that will resist shear forces.  The full-height segments are then designed to resist the applied loads.  Hold-down connectors (HD) are required at the bottom corners of each segment to prevent each segment from overturning.

          The following  illustrations depict a typical shear wall.  Figure 1 shows that the wall is made up of six sheathing panels, typically plywood or oriented strand board (OSB), that have been mounted vertically to the framing members.  Holes have been framed into the wall to accommodate a window and a door.  This wall geometry will be used several times throughout this tutorial.
 


Figure 1 - Wood-frame wall with openings


Figure 2 - Segmented shear wall model

 
          Figure 2 illustrates the shear wall divided into full-height sheathing segments, shown in green.  Only the full-height sheathing segments are assumed to provide resistance to lateral loads.  The sheathing grade and thickness and the nail size and spacing determine the shear capacity per foot of length of the full-height segments.  IBC Table 2306.4.1 and UBC Table 23-II-I-1 relate these variables so that designers can determine the shear capacity (v) in units of lb/ft (plf) of the full-height segments.  The design shear capacity, V, is found using the following equation:
 

V = v Sbi

Where:

V = total allowable shear capacity of wall (lb)
v = allowable shear capacity per unit length (lb/ft)
Sbi = sum of lengths of full-height sheathing segments
 
 


Topics of this module include:

Introduction, Load Path, UBC Design Table, Wall Shear, Dimension Ratios, Chord Design
 Anchorage, Deflection, Perforated Design Method, Method Comparison, Shearwall Failures

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