Title: Load and Resistance Factors for Concrete Bridges and Buildings
Author(s): Olga Iatsko and Andrzej S. Nowak
Publication: Symposium Paper
Appears on pages(s): 19-31
Keywords: load factor, resistance factor, design point, reliability index, dead load, live load, resistance, statistical parameters, bias factor, coefficient of variation
In the new generation of design code, safety of structures is provided in form of load and resistance factors. Safety is measured in terms of the reliability index. The acceptability criterion in the selection of load and resistance factors is closeness to the target reliability index which can be different depending on limit state. The paper presents a procedure to determine these factors using the concept of “design point”. The coordinates of design point are equal to factored load or factored resistance. The required input data includes for each load component and resistance: mean values, bias factor (ratio of mean to nominal), standard deviation or coefficient of variation. The procedure is demonstrated on example of bridge design code (AASHTO) and design code for concrete buildings (ACI 318) for prestressed concrete girders and reinforced concrete beams in flexure and shear.