Event Date
Abstract
Floats, such as for ferry terminals, ferry maintenance facilities, and other floating waterfront structures, often rely on long vertical piling to provide lateral support while allowing the floating structures to move up and down with changing water levels. These structures are often considered seismically isolated due to the resistance and damping of the surrounding water and are often designed without seismic evaluation.
This presentation is based on experience with various projects in the San Francisco Bay Area and presents design ground motions and detailed findings from the seismic analysis of two ferry terminal floats, one concrete and the other steel, and a 95 ft x 173 ft (29 m x 53 m) steel float supporting
a two-story floating fire station. Findings focus on the effects of water resistance, soil damping, and the gap between the pile and float. Results will be useful in understanding the significance of these factors for other projects.
An innovative simplified spreadsheet method and time-history analyses are presented, along with an approach used for estimating soil damping. The analyses show that water resistance is less significant than expected, and that seismic accelerations and motions are large, such that seismic evaluation of these structures is recommended for regions with high seismicity.
There are many similar structures worldwide. We hope this presentation is helpful for designers and owners of pile moored floating structures in areas with significant seismic risk.
Biography
Erik Soderberg is Liftech’s president and a structural engineer with over 29 years of experience in the design, review, and modification of a variety of structural systems including dozens of wharves, the design of over four miles of wharves and crane girder systems, hundreds of container cranes, and over a dozen bulk loader structures.Other structures include crane lift and transfer systems and concrete and steel floats. During Erik’s time at Liftech, the company has received several awards and recognitions including the elevating girder crane, Left Coast Lifter 1,700 t floating crane, South San Francisco Ferry Terminal, seismic friction damper, and Congressional Recognition for “pioneering the structural designs for the world’s first high speed, dockside, container handling crane, and in recognition of outstanding and invaluable service to the community.” He represents Liftech at many conferences and several of his papers and presentations are published.