Shearwall Design

Important Note – These are descriptions to changes implemented in WoodWorks Shearwalls for version 9 and may not reflect current behavior.

1. Seismic Design Category Restrictions

   The limitations on seismic design categories that materials can be used for given in IBC Table 2306.7 note a, referring to ASCE 7 12.2-1 and in SPDWS 4.3.7.5 for gypsum wallboard and other gypsum or plaster materials, SDPWS 4.3.7.4 for fiberboard, and SDPWS 4.3.7.6-9 for lumber sheathing, are now imposed by setting the shear capacity for those materials to zero if it is a prohibited seismic design category.

   Previously the program merely warned the user on the screen that prohibited materials were being used, and placed a message under the Seismic Information table, but went ahead and allowed you to design for these materials anyway. No message appeared under the shear results table. Notes now appear under the Sheathing Materials table, the Seismic Information table, and the Shear Design table. Refer to for more details .

2. Seismic Height-to-Width Factor
   1. Design Shear based on Rigidity with Seismic Factor (Bug 2187)

      When the Distribute forces to wall segments based on rigidity option was selected in conjunction with the Use shearwall capacity to approximate rigidity option, the design shear distributed to each segment was not taking into account the seismic height-width factor from SDPWS.

      This resulted in walls with H-W factors less than one to be given more design shear than they should have been, and the other walls on the shearline received less design shear than they should have. Since the program designs for the walls with the low height-to-width factor, this created conservative designs.

   2. Combining Seismic Height-to-width Factor (Bug 2190)

      When there was more than one full-height segment on a wall, the program was using the weighted average of combined height-to-width factor of all the individual segments’ height-to-width factors, instead of the minimum height-to-width factor of any segment in the shearwall. This resulted in the design wall for a shearline using a larger height-to width factor than it should have, and non-conservative design.

      This also affected the calculation of redundancy factor ρ, when checking whether on walls resistance is greater than 35% of resistance of the story.