ABSTRACT
This chapter outlines the philosophy behind what Europeans call limit state design and Americans call load and resistance factor design. The factor of safety (FoS) is not a formal part of limit state design process and it is completely different from the partial safety factor. The FoS can be used to identify the first mode of failure for a given structure. For example, if the FoS is calculated for every failure mode in a bridge, then the failure mode with the lowest FoS is likely to fail first. The working load is the load calculated in the absence of partial safety factors; therefore, it is the same as the serviceability limit state load. When new design equations are added to codes, they are tested for accuracy in the laboratory. It is important to remember that design resistances and loads are only approximations.
