Variability in Geometry and Imperfections of Surface Ship Structural Scantlings

摘要

Random behavior of strength variables of a structure can cause the strength ofthe structure to vary beyond acceptable levels. The design strength is based on nominal values for variables such as yield stress of the material, plate thickness, modulus of elasticity, and so forth. The actual values of these variables are often different from the nominal, or design values. Understanding the randomness of the basic strength variable behavior allows the designer to account for this in the design strength of the structure. The basic structural strength variables may be classified into material variables, such as yield strength and ultimate strength, and geometry or construction variables, such as plate thickness and stiffener height. The objective of this study is to quantify the randomness or uncertainty found in the geometric variables used in the analysis and design of surface ship structures. The bulk of the data used in this study are for U.S. Navy ships. Additional data is provided for U.S. Coast Guard and commercial vessels. The results of this study can be used in the development of reliability based design criteria, tolerance limits, and the assessment of uncertainty in strength predictions.