An interesting two part series of articles authored by Prof. Dr. Graham Powell. Prof. Powell is Professor Emeritus of Structural Engineering at the University of California at Berkeley. Over his career, Professor Powell has developed, or supervised the development of, several computer programs that have been used widely in research and industry. He currently works as a consultant to Computers and Structures Inc., developing and supporting the CSI PERFORM computer program. Professor Powell may be reached at firstname.lastname@example.org.