Opinion Paper Unexpected Stress Failures during Earthquakes

At present it is the consensus that structures should be desitned to undergo ductile deformations if subjected to very strong ground shaking, so structures designed without consideration of large deformations can be expected to experience undesirable damage. However, in most strong earthquakes some unexpected ground motion or unexpected structural failure occurs which deserves closer examination. In both the Northridge and the Kobe earthquakes there were unexpected ground motions as well as unexpected structural damage. The reason such failures are unexpected is that their possibility was not identified during the design process.