RESISTANCE FACTORS AND COMPANION-ACTION LOAD FACTORS FOR REINFORCED-CONCRETE BUILDING DESIGN IN CANADA

The currently used safety factors for concrete buildings do not reflec t current levels of quality control, refined knowledge of variabilitie s as established by recent studies, load-resistance correlation in the tension failure of columns, and so on. Revision of load combination m ethods can also achieve more consistent reliability. The primary objec tive of this investigation is to develop an optimum set of load and re sistance factors for the design of reinforced concrete buildings in Ca nada. The companion action load factor format is selected because it m odels real load combinations more accurately than the probability fact or format that is used in the National Building Code of Canada and CSA Standard A23,3-94. The reliability analysis is based on a variable li mit state equation developed by combining the ''true'' limit state, wh ere the structure is about to fail, and the design limit state that is used in the design office. Present levels of quality control and pres ent specifications are reflected in the variables used. Resistance fac tors for concrete and non-prestressed reinforcement are calibrated for use with the companion-action load factors developed in this study. T he resistance factor for concrete is increased, leading to a general i mprovement in economy. Adequate and more uniform safety is achieved th rough revised load combinations and factors.