Story Drift

For both wind and seismic design, the program determines the lateral deflection of the top of the walls on each shear line relative to the bottom of the wall, and compares with the maximum allowable deflection.

This calculation is made on each level, and for each force direction ( E->W, W->E, N->S, S->N). Results are shown in the Story Drift table of the Design Results. If a failure exists on any story or direction, it is reported in the Design Summary

Post-design Check

Note that this check is not included in the Shearwalls design routine for unknown wall materials. Shearwalls designs walls to resist shear loads and C&C wind loads, and then checks the designed walls for story drift. So a set of wall materials that passed the shear wall design process can fail the storey drift check.

This approach is taken for two reasons -

• Different walls on a shearline can have different materials, and the design process for a single wall occurs before we know the deflection for the entire shearline.
• It is not only wall materials that influence deflection, often the largest component is the hold-down displacement term. There is not currently an iterative design for hold-downs, and even if there was, it would be prohibitively complex to optimize for both hold-downs and wall materials simultaneously.

Suppressing Storey Drift Output

You can suppress the output of story drift check using either the Show/Hide menu or the Display Options settings. Doing so will also suppress any warnings that would appear in the Design Summary.

You can do so separately for wind design and for seismic design.