Offshore Technology Research Center


Abstract ID# :


Report Title:

Upper Bound Method Program for Inclined Load Capacity Calculation of Suction Caissons


Yuqing Wu, Texas A&M University

Report Date:

May, 2004

Note: This study is part of a broader project "Suction Caissons & Vertically Loaded Anchors: Design Analysis Methods" (MMS Project 362).

Suction caissons are large, vertical pipes, closed at the top and open at the bottom, for offshore facilities. They are installed by pressure drawdown within the cylinder, referred to as "suction", after partial penetration of the cylinder due to its dead weight. They may have significant advantages over conventional piles and have been used for both fixed foundations and anchors for a variety of offshore structures [1]. However, our understanding of suction caisson behavior is still limited due to lack of database. There are several ways to help us to predict the caisson capacity: model test, FEM analysis and other numerical methods.

"If an estimate of the plastic collapse load of a body is made by equating internal rate of dissipation of energy to the rate at which external forces do work in any postulated (kinematically admissible) mechanism of deformation of the body, the estimate will be either high or correct" (Drucker, 1952). The upper bound method has been used extensively in research and engineering over the past 50 years e.g. Drucker and Prager (1952), Chen (1975) and Murff and Miler (1977), Murff and Hamilton (1993) etc.

This technical report describes the study of inclined load capacity calculation of suction caissons in Directed Study-CE685 course instructed by Dr. Aubeny and Dr. Murff. To estimate the inclined load capacity of suction caisson, a simplified calculation model ( Fig 1) based on an upper bound plasticity limit theory was built by Aubeny et al [1]. Based on this calculation model, a visual basic application program SAIL was compiled. The program is interactive with spread sheet that has a powerful solver optimization algorithm. By using this program, a series of cases are calculated. Through case analysis, the effects of some parameters on caisson capacity are demonstrated.

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