A New Robust Design Methodology to Improve the Reliability of Structural Beams

Safety factors have been used widely in the design of beams for many years. It is still the major design method used in the industry. The advantage of using safety factors is that it is simple and easy to understand by the designer. However, the disadvantages of using it are that the product may be under-designed or over-designed depending on the safety factor value chosen, and the designers do not know what reliability they have designed into the product.

In this paper, a new Robust Engineering Design-By-Reliability method is introduced. Using this method, the designers are able to know the designed-in reliability of their beams at the outset, thus avoiding the under- or over- design situations. Also in this paper, the safety factor based method and the Robust Engineering Design-By-Reliability method are compared. From the comparison it can be seen that the Robust Engineering Design-By-Reliability method is much more cost effective. Four design examples are provided to illustrate the application of the Robust Engineering Design-By-Reliability methodology to the design of all types of beams.