Seismic horizontal irregularity

[bnickeson]

I have a parking garage that has a horizontal irregularity Type Ib: extreme torsional irregularity due to having a shear wall down the middle of the building and one on the east side (none on the west side). In the other orthogonal direction, I have no torsional irregularity, as both shear walls are equidistant from the center of mass. So since I have an irregularity in one direction, do I have to apply the requirements for that irregularity in both orthogonal directions or just the direction in which the irregularity takes place? For instance, ASCE 7-05 says to increase the diaphragm and collector connections by 25%, but does that also apply to the direction in which I am not irregular? It wouldn't make much sense if I had to, but then again there's no where that I can find in the code that explicitly states that.

Thanks.

 

[ishvaaag]

In my opinion, you can proceed without applying the requirements of irregularity in the direction the system is regular, i.e., you follow a per hypothesis basis; but when considering the case where torsional deformation is induced, the forces in the collectors of the perpendicular direction, obviously generated by the torsion, should follow the enlargement of solicitations, and they -at least theoretically- might control the design, unknown till not proven. This is a solution that respects the idea of that torsionally induced forces may need a bigger safety factor whereas it does not go over-conservative for the direction in which the forces are regularly taken.