A revolutionary seismic isolation system—provided by Casper, Phillips & Associates Inc.(CPA)—has been installed on two quayside container cranes for the first time this year.
The crane base anti-seismic isolation system is built on nonlinear time history analysis(NLTHA) and can protect the crane main structure from damage even in contingency level earthquakes. BASIS has been successfully installed and commissioned on two cranes that are in a major seismic zone in Turkey. The cranes, installed at Asyaport, have a 100ft.(30.48m) gantry span, 223ft.(68m) outreach, 66ft.(20m) back-reach, and 152ft.(46.3m) lifting height above the gantry rail.
CPA, which has been utilizing NLTHA for research and engineering projects since 1991, offers a wide variety of heavy-duty industrial services, including procurement, specification, design, manufacturing review, modification, and accident investigation.
BASIS is installed between the sill beam and main equalizer beam, about 13ft.(4m) to 16 ft. (5m) from ground level depending on the crane’s size. It includes two friction damper assemblies, two energy restoring device assemblies, a guiding device, and two friction damper locking devices.
Mike Zhang, the head mechanical engineer at CPA, said: “The initial container crane isolation system that we developed included dampers in both gantry travel and trolley travel directions. [NLTHA] analysis revealed that the base shear in the gantry travel direction varied within only 5% between a crane with a seismic isolation system and a crane without it. However, in the trolley travel direction, the base shear is significantly reduced by incorporating our seismic isolation system. Therefore, to reduce costs while maintaining a high level of effectiveness, our final seismic isolation system is designed to operate only in the trolley travel direction.”
Zhang, who has co-authored a white paper on the BASIS concept with Jeffery Hubbell, the head structural engineer at CPA, explained that ports located in seismic zones and crane manufacturers are both taking note of the system. Typically, he said, the ports specify the seismic requirements, while the crane manufacturers propose the isolation system. The port then makes the final decision on the proposed purchase.