Statistical variation of reinforced concrete structure strength.

This investigation involved the fabrication and testing to failure of a large number of nominally identical reinforced concrete members such as 20 simple beams, 20 two-span continuous beam and 20 columns. The simple beams were of rectangular section 5" wide by 8" deep with 2-#5 bars as tension reinforcement only. The simple beams were loaded to failure using equal loads at the third points. The two-span continuous beams, also of rectangular section 5" x 8" had both tension (2-#5 bars) and compression (2-#5 bars) reinforcement, equal loads were applied at the centre of each span. The column was rectangular in section (6" x 6") with symetrical reinforcement of 4-#5 bars. The column was loaded to failure by an eccentric load. The distribution of load carrying capacity of the members was determined by finding the joint probability of a given concrete strength and steel yield stress occurring and calculating the ultimate load using a prediction formulae. From the comparison of the results, it was found that the experimentally determined mean strength of the beams and columns were in good agreement with the ultimate loads which were calculated from the prediction formulae of the National Building Cade of Canada and the building code requirement of the American Concrete Institute. From the predicted distribution of ultimate load capacity the probability of the ultimate load being less than the design load was determined. Using the &phis; factors recommended by the NBC. The probability of failure for the columns was less than 0.01% and 7% for the beams