CompuServe Messages

Hi, Phil. I lived in Glendale during the Sylmar quake in 1971. I am also a structural engineer now residing in San Diego. The quake appears to have had a significant vertical component. Since the Oakridge fault is a thrust fault this is not surprising. The problem is that our building codes do not account for vertical accelerations exceeding 15% of G. I think that will now need to be revised. This is important in buildings that have a "transfer" level of framing. An apartment built over parking is an example. Because the spacing of parking spaces does not fit neatly with the typical widths of apartments beams are frequently used to transfer forces from walls above to columns below. With a significant vertical component of acceleration these beams can be overstressed and fail. Even if they don't fail they can be bent so much that they will be pulled off their supports. The San Andreas is a transverse fault and will generate far less in the way of vertical acceleration. It's horizontal components, though, will be whoppers. These are accounted for, however, in current codes. It appears that a code revision is in the offing. Mark