Our article in the summer 2012 edition of Port Technology International, ‘Seismic protection of quay cranes’, addressed the application of friction dampers in quay cranes. This is the second article of a three-part series on crane seismic issues. This article focuses on seismic design considerations for new cranes. A third article, to appear in the winter 2012 edition, will address seismic retrofit for existing cranes.
Earthquake forces and crane evolution
The size and weight of quay cranes has nearly tripled since the introduction of the first cranes in 1959. Early cranes servicing Panamax vessels weighed 500 tonnes with a 15 meter rail gauge. Modern cranes, capable of servicing post-Panamax vessels and larger vessels weigh 1,200 tonnes or more, with a 30 meter or wider rail gauge. Since cranes are now much larger, seismic forces are much larger as well.
While cranes have evolved during the last 50 years, in most cases the seismic design has not. For decades, industry specifications required that crane structures resist lateral seismic forces of 20 percent of gravity, 0.2 g. The seismic forces on smaller cranes are limited to the forces required to tip a crane and lift the legs off the rail…
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