Bottom-Supported Concrete Platforms: Overview

A concrete gravity platform consists of a cellular caisson made up of a collection of large concrete cylinders supporting three or four large diameter tubular columns with a steel frame deck structure on top. The huge size of the overall structure, and the variety of load conditions, make it complicated to analyze all of the problems with one structural model. The complete soil-structure-water system is divided into separate systems for analysis, and then the load cases are combined with due regard for interaction effects to determine the total response. Three general classes of analyses are involved: (1) Space frames; (2) continuum type shell problems; and (3) soil-structure interaction problems. Methods of predicting elastic-plastic-fracture behavior and implosion pressure on the outer cell walls are mentioned. Kinds of failure of gravity type foundations for offshore structures are given.