Statistical Evaluation of Load Factors in Structural Design

A procedure leading to the determination of load factors is formulated based on the following criteria: 1) The load factors should provide a desired level of structural safety with respect to all loading configuration. 2) This desired level of reliability may be determined by economic factors such as cost of construction and the cost of failure of the structural system. 3) Load factors for individual element design may be determined by the desired level of reliability of the whole system. 4) Additional information about the loading environment and the material strength characteristics can be systematically incorporated into the procedure to obtain a better set of load factors. 5) The procedure to evaluate load factors should be simple in form and easy for application. In the formulation that is presented here, dead, live, wind and earthquake loads are included. First, the load factors for a given reliability level for a structural element are calculated and second, the optimal reliability level of the structural system, its relationship with element reliability and the economic considerations in determining optimal reliability are considered. Step by step procedure is outlined and numerical example is worked out to illustrate the simplicity of the procedure.