POST LOMA PRIETA EARTHQUAKE ON THE CYPRESS STRUCTURE
Following the Loma Prieta earthquake in 1989 the elevated freeway known as the Cypress Freeway in Oakland suffered catastrophic failure. May sections of the freeway collapsed onto a lower level often referred to as pancaking. There were a few sections of the freeway left standing that were going to need to be taken down. This offered Caltrans a unique opportunity to do testing on the structures, as there were many bridges and elevated sections of freeway built in the same time frame.
As you can see in a few of the attached pictures one of the primary causes of the collapse was the lack of spiral wrapping of the vertical rebar.