Casper, Phillips & Associates Inc. Install New Seismic Isolation System On Cranes in Seismic Activity Zone
Casper, Phillips & Associates Inc. (CPA) have installed a new seismic isolation system on two quayside container cranes in a major seismic activity zone in Asyaport, Turkey. The cranes have a 100 ft. (30.48m) gantry span, 223 ft. (68m) outreach, 66 ft. (20m) back-reach, and 152 ft. (46.3m) lifting height above the gantry rail.
The crane base anti-seismic isolation system (BASIS) is built on nonlinear time history analysis (NLTHA) and can protect the crane main structure from damage even in contingency level earthquakes.
BASIS is installed between the sill beam and main equalizer beam, about 13 ft. (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.
CPA 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.
Source Casper, Phillips & Associates Inc./BridgerHowes