Seismic Design of Marine Caisson Waterfront Structures

The objective of this paper is to describe state-of-the-art procedures for seismic design of concrete caisson structures in a marine environment. The proposed caissons are cellular self-floating reinforced concrete structures that are prefabricated, towed to the project site and submerged to their final position. They are often used as waterfront retaining structures or as breakwaters for new ports, and LNG terminal developments. This paper investigates caissons of representative dimensions located at a typical water depth. The paper is concerned with the seismic design using the finite element method in a combined model for both structural and geotechnical design of the caissons and the foundation. The structural design is driven by seismic soil loads from fill behind the caissons and inside the caisson cells. The soil-structure interaction is modeled through non-linear time-series. Seismic foundation design of waterfront structures is often performance based with maximum allowable permanent displacements of the caisson as the design criteria. Structural design of the cellular walls is based on effective soil pressures. Results, in terms of maximum displacement, caisson tilt and soil pressures are presented and compared to conventional design methods available in the literature.