Shear Wall Design

Chord Design
 

         The vertical members at either end of a shear wall are called chords.  In the Segmented Shear Wall (SSW) design method, chords are provided at each end of every shear wall segment (i.e., on either side of every door or window opening, and at corners/ends of walls) and are designed to resist the moment acting in the shear wall segment. In the Perforated Shear Wall (PSW) shear wall design method, chords are only provided at each end of the entire shear wall and are designed to resist the entire moment acting in the shear wall.   The moment subjects the chords to axial loads, either compression or tension.  

          A typical method of analysis for chords in wood-frame walls is to use the overturning moment in the shear wall (or shear wall segment) to determine chord forces.     


  

Overturning Moment:
M1 = v * b1 * h M2 = v * b2 * h
     

Chord Forces:

T1 = C1 = M1 / b1  =  vh T2 = C2 = M2 / b2  =  vh
         
  

        Chords must be designed for both tensile and compressive forces.  The compression chord may also carry gravity loads in addition to the forces associated with the overturning moment. The tension chord may need to resist wind uplift forces in addition to the forces caused by lateral loads.   In order to resist the large tensile and compressive forces, chords are typically composed of doubled full height studs.  

          Because the chords may be subjected to very high axial compression forces it is important to consider the sill plates that the chords bear on.  Crushing of the sill plates (bottom plates) is a common mode of failure for shear walls subjected to large overturning moments.  Therefore, when designing the sill plates, compression perpendicular to grain strength of sill plates should be considered.  

 


Topics of this module include:

IntroductionLoad Path, Segmented Design Method, UBC Design Table, Wall Shear, Dimension Ratios
 Anchorage, Deflection, Perforated Design Method, Method Comparison, Shearwall Failures

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