RMS-1: Application of System Reliability Analysis to Offshore Structures

Until recently, structural engineering has been largely dominates by deterministic thinking. This was reflected by a generation of design codes specifying minimum resistance properties end load intensities based mostly on past experience. Inherent in those codes were high safety factors which usually resulted in safe (but not necessary economical) designs. This led some engineers and also the public lo think that absolute safety can be achieved. Unfortunately, structural failures end their sometimes dramatic consequences happen lo remind us thot absolute safely is not achievable and therefore that some risk of unacceptable performance must be tolerated. This Implies that risk must be quantified and controlled. Hence the development of a new generation of probabilistic codes and of a new branch of civil engineering. usually referred to as structural reliability analysis. Clearly. some structures call for more attention than others as far as reliability is concerned. These are the structures having large failure consequences. i.e. loss of lives. economic losses, and environmental damages. Offshore structures typically fall in that category. Moreover. they are placed in an environment which is random in nature, and hence, requires a probabilistic approach In order to be properly accounted for in the design. The general subject of this dissertation is the application of recently developed structural reliability analysis techniques to offshore structures. Before describing the objectives of this study more precisely and in order lo understand better the motivations behind it, it will be useful to start with a brief review of the state of practice in structural reliability analysis.