Practical method for determining load and resistance factorsusing third-moment transformation

Load and resistance factor design (LRFD) is a suitable format for the reliability-based limit state design of structures. It has been adopted in many countries, such as the United States, Europe, Canada, and Japan. Usually, the first-order reliability method (FORM) is used to estimate the load and resistance factors, but it requires the determination of design points and complicated double iterative computations. Therefore, FORM is not easy or practical for engineers to use. This paper presents a simple, accurate method to determine the load and resistance factors utilizing the third-moment transformation, which does not require derivative-based iterations and can estimate the load and resistance factors without using the distribution of random variables. In addition, the proposed method provides enough accurate results within a wide range of target reliability indices. Therefore, this method should be effective and convenient for calculating the load and resistance factors in actual practice. Five numerical examples illustrate the proposed method's efficiency and accuracy; FORM provides a benchmark for comparison.