Also, on the topic of joints, there are a couple of companies out there that have designed and tested (UC@Berkely) seismic modular expansion joints. Joints tested at velocities of 40 inches/second, large transverse and longitudinal movements. The testing was done in order to fulfill Caltrans...
Another source of error may be the small strain assumption used in linear FEA. ALGOR had an excellent demonstration of this effect on one of their webcasts - on the same cantilever beam example. The differences are pretty dramatic. It may be true that the displacements are relatively small...
At 8" of displacement, isolators or dampers might be an attractive option - keep the displacements down with added damping and you might not need keeper plates. I've heard that GT STRUDL was coming out with a bilinear hysteretic element, that may be of help. You've got to be careful when...
