Authors of pushover analysis honored

RESTON, Va.—The American Society of Civil Engineers recently initiated the Hall of Fame as a way of honoring technical papers presented at the Offshore Technology Conference (OTC) and their authors, whose innovation and vision have had a lasting influence on the design, construction, and installation of the offshore infrastructure. One of the honors went to a structural engineer who revolutionized ultimate strength and reserve capacity design. Paper 2357, presented at the OTC in May 1975, titled, "Inelastic Analysis of Fixed Offshore Platforms for Earthquake Loading" was authored by structural engineer Joseph Kallaby, P.E., and David N. Millman, P.E.

The paper introduced a method—commonly referred to as pushover—that highlighted the important role that ductility and reserve strength play in the design and assessment of platforms or other structures under extreme, or "ductility level," earthquake events. It formed the basis of the revolutionary new earthquake criteria—adopted by the American Petroleum Institute in 1975—used in establishing platform ductility and reserve strength. More than a decade and a half later, it was incorporated into design standards to evaluate reserve strength under storm conditions. It spurred tens of millions of dollars in research and testing in the United States and Europe to understand and quantify the behavior of space-frame structures up to collapse. It is now used worldwide and is incorporated into all major analysis software. It also forms part of standard structural engineering practice in the performance-based evaluation of buildings.

The paper also proposed the dual criteria of providing adequate stiffness for elastic strength design, and ductility for reserve strength to survive major earthquakes and other severe loading.

Kallaby is the founder and president of Offshore Structures, Inc. (OSI), of Houston, Texas. He has extensive experience in structural engineering and marine structures, having served internationally as a consultant and written extensively on their design. To receive a copy of the paper, please contact him at osi-jk@swbell.net.