Reliability - Based Sensitivity Assessment of Design Parameters for Steel Section Members under Compression and Bending

Abstract

The sensitivity of design parameters for members subjected to axial compression and bending stresses were assessed using linear fitting of the sensitivity curves. Design loadings were obtained from an analysis of idealized five - story steel structure and EC3 design provisions were u s e d to design members of the framed structure. First Order Reliability Method (FORM) coded in FORM5 was used for the reliability analysis and values of the design parameters were varied from -15% to 15% at an interval of 5%. The result of the linear fits provides a satisfactory representation of the curves from which the coefficient of sensitivity for each design parameter was obtained. The result showed that yield strength is the most sensitive parameter with an average degree of sensitivity (DOS) of 27. At lower axial stress the plastic section modulus (Zp) is second most sensitive with DOS of 15⁰ and cross sectional area (A) is the least sensitive with 13⁰. At higher axial stresses, cross sectional area is second to yield strength with 15⁰ while plastic section modulus is the least sensitive with 13⁰ The result of the study also shows that members under a combination of low axial stress and high bending moment and also high axial stress and high bending moment result in low structural safety of a member. The study therefore recommends that for design of members under low axial stress and higher bending moment, sections with higher plastic section modulus. For members under high axial stress and bending moment, sections with high cross sectional area as well as high plastic section modulus are recommend for their design.