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Reliability models for circular concrete columns
Development of reliability model for the short circular reinforced concrete columns and performance reliability based calibration for new strength reduction factor were studied in this dissertation The latest statistical data were used in the calibration procedure. Rational strength reduction factors corresponding to load and load-combination factors specified by ASCE 7-02 and adopted by ACI 318-08 Code were determined. Recommended strength reduction factors are proposed to be included in ACI Code, in addition to the existing provisions for resistance factors for rectangular column. For the scope of this research an analytical model for representation of behavior for circular reinforced concrete eccentrically loaded columns was developed. A software which determines capacity for circular columns was created. Using this software, the interaction diagrams for force and bending moment in regards to the investigated columns were generated. Subsequently, Monte Carlo simulations were performed for several design cases with different compressive strengths of concrete and reinforcement ratios. In each of the design cases, the failure zones were determined and the statistical parameters of resistance were calculated. The target reliability index was assumed as βT = 4.0 and it corresponds to the probability of failure Pf = 3.17 * 10–5. Based on this and the determined statistical parameters of resistance, the resistance factors, ø, for circular columns were derived. There are also some additional findings related to columns behavior in this dissertation. Besides to the main scope, a simplified method for calculating nominal ultimate strength capacity was proposed. Another outcome of this study is the provision of the design nomograms. They present normalized interaction diagrams allowing to obtain the nominal resistance for circular columns. They are found to be a very useful design tool for structural engineers.^
Lutomirski, Tomasz A, "Reliability models for circular concrete columns" (2009). ETD collection for University of Nebraska - Lincoln. AAI3350450.