Seismic Guidelines for Container Cranes

Abstract

Historically, seismic forces have not been a concern for early container cranes, which were lighter and less stable than today's larger jumbo cranes. During an earthquake, the earlier cranes would lift from the rails before significant inertia forces could develop in the crane structure. Current large cranes, with 100-foot or greater rail gages, are much heavier, which results in significantly larger seismic forces in the crane structure. Liftech has performed time-history analyses of A-frame and low profile jumbo cranes. Our studies indicate that many jumbo cranes will be extensively damaged in moderate earthquakes, and that many jumbo cranes will be severely damaged, or will collapse, in a major earthquake. Container crane seismic design criteria are changing to address the seismic risk to jumbo cranes. Several upcoming design standards, one from the American Society of Civil Engineers, and others from ports, will specify seismic performance requirements for new cranes. This paper presents the following: 1. Expected seismic performance of cranes built to early design criteria 2. Recent design standards and their crane seismic performance requirements 3. New crane seismic design criteria, their effect on the crane design and costs 4. Options for retrofitting existing cranes