Most have identified vibration as the driving difference, but when I did a comparison between the two methods I found differences mainly occured because the NBC tables use limit states design, while the IRC uses allowable stress design to achieve their respective spans. Make sure you are also...
If flexible diaphragm is all you plan on doing, specify a shearwall where you intend to put your strong wall and grab the load from the model to design your strong wall by hand. If you are also doing rigid diaphragm design there is an option to specify the relative rigidity of your walls in the...
