Quantifying Quality Improvement Programs

by Joseph F. Murphy, Structural Reliability Consultants, United States,



Document Type: Proceeding Paper

Part of: Probabilistic Methods in Civil Engineering

Abstract:

Structural codes are evolving to a limit state design basis in which the safety checks are derived from the underlying probability distributions of strength and loads. An example safety checking equation is: ? R_n?1.2 D_n+1.6 L_n where 1.2 and l.6 are load factors on nominal dead and live loads, D_n and L_n, and ? is a resistance factor on nominal resistance, R_n. For specific probability distributions of dead and live loads, D and L, and resistance R, a reliability index ? can be calculated as a function of the resistance factor ?. If ? is held constant, the increase in ? quantifies the increase in reliability. If ? is held constant, the increase in ? quantifies the increase that can be taken on the nominal resistance, R_n, of the original distribution. Two processes are presented: a process which selectively removes material (with a specified or measured removal efficiency) from the lower tail (below a specific strength); a process which removes material based on a correlated variable. Material is removed with 100% efficiency on the correlated variable below a specific set point.

Subject Headings: Load and resistance factor design | Strength of materials | Materials processing | Structural safety | Probability distribution | Probability | Load factors

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