Code Sections and Analysis - The Analysis of Irregular Shaped Structures - page 7

4.1.1 Design requirements
The proportioning, design and detailing of engineered wood systems members,
and connections in lateral resisting systems shall be in accordance with the refer-
ence documents in Section 2.1.2 and the provisions of this chapter. A continuous
load path, or paths, with adequate strength and stiffness shall be provided to
transfer all forces from the point of application to the final point of resistance.
4.1.4 Boundary elements
Shear wall and diaphragm boundary elements shall be provided to transfer the
design tension and compression forces. Diaphragm and shear wall sheathing
shall not be used to splice boundary elements. Diaphragm chords and collectors
shall be placed in, or tangent to, the plane of the diaphragm framing unless it can
be demonstrated the moments, shears, and deformations, considering eccentrici-
ties resulting from other configurations can be tolerated without exceeding the
framing capacity and drifts limits.
4.2.1 Application requirements [partial quote]
Wood diaphragms shall be permitted to be used to resist lateral forces provided
the deflection in the plane of the diaphragm, as determined by calculations, tests,
or analogies drawn therefrom, does not exceed the maximum permissible deflec-
tion limit of attached load distributing or resisting elements. Framing members,
blocking, and connections shall extend into the diaphragm a sufficient distance to
develop the force transferred into the diaphragm.
4.2.2 Deflections [partial quote]
Alternatively, for wood structural panel diaphragms, deflection shall be permit-
ted to be calculated using a rational analysis where apparent shear stiffness
accounts for panel deformation and non-linear nail slip in the sheathing-to-framing
connection.

1.5 Complete Load Paths

Irregular-shaped structures similar to the one shown in Fig. 1.1 are commonly designed
without properly addressing the irregularities contained therein. Tie straps with block-
ing are often randomly placed throughout the structure without explicit purpose, in an
ambiguous attempt to provide a solution to the irregularities, and are seldom supported
by calculation. All the connections that are required to develop a complete load path are
often ignored, even along straight lines of lateral resistance. ATC-7 4 noted that failures
have occurred for the following reasons:

• Connection failures were caused by incomplete load paths, incomplete designs,
inadequate detailing, and inadequate installation (construction). Often, deter-
mination of the size of wood chords for tension and compression forces is also
ignored in the design, which ensures failure.
• Designs included diaphragm shears and chord forces only, no connection
designs.
• Designs did not include load paths that continued down to the foundation and
into the soil.
• Designing to the maximum diaphragm and shear wall capacity (close nail-
ing), while limiting the number of shear walls to a minimum (no redundancy),