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For seismic design only, Shearwalls implements NBC 4.1.8.13 by checking the maximum amplified story drift for any shearline against the allowable limits on each level, and for each force direction (E->W, W->E, N->S, S->N).
Storey Drift Calculation
Maximum Deflection
The maximum deflection is the largest deflection on any shearline, calculated as described above. If deflections on a line have been equalised (see Shear Distribution to Wall Segments Within Shearline ), it is the common deflection of all walls on the line. If not, it is the largest deflection for any segment on the line.
Deflection Amplification Factor
The deflections are multiplied by the amplification factor from 4.1 8.13 (2) : Rd Rd / IE . The R values can be input into the Site Dialog, but unless they were over-ridden, they are the values from NBC Table 4.1.8.9
The importance factor IE calculated from the Occupancy category entered in the sited dialog is used.
Allowable Drift Calculation
The allowable drift is calculated according to NBC 4.1 8.13 (3)..
Story height
The storey height hs for each level is the wall height plus the upper floor thickness.
Occupancy Category
The existing input for Occupancy category from the Site dialog is used.
Provisions Not Implemented
Sway Effects
The program does not implement NBC 4.1.3.2(12) regarding sway effects, that is, the effect of vertical loading acting on the structure in its displaced configuration. .
Rotational Deflection
The program does not consider the effect of rotation, that is, the deflection that is caused by the fact that walls on upper floors are rotated due to the deflection on the floor below. This deflection is not mandated in the NBC or CSA O86, but is addressed in the APEGBC Technical and Practice Bulletin for .5 and 6 Storey Wood Frame Residential Building Projects. We hope to implement this in a future version of the program
Output
A new table has been added showing the storey drift calculations for each level and force direction on that level, and indicating success or failure of the storey drift check. Refer to Deflection Output for details.