EXPERIMENTAL RESEARCH ON CREEP OF CONCRETE FILLED STEEL TUBES UNDER ECCENTRIC COMPRESSION

Creep experiments of two groups of CFT eccentric compression members with eccentricity, concrete strength grade and loading age as parameters were carried out. Then 6 commonly used creep prediction models were compared and analyzed. The results from experiment indicated that with the increase of eccentricity, the maximum creep strain (near load side) of CFT eccentric compression members was larger, and the relationship between eccentricity and creep strain was basically linear. The higher the strength grade of concrete was, the smaller the maximum creep strain (near load side) of eccentrically compressed specimens was. Compared with C50 specimens, the creep strain of C40 specimens with loading age of 14 d increased by 12.2%, 26.0%, 21.7% and 23.7% respectively at 60 d, 120 d, 180 d and 240 d. The earlier the loading age was, the larger the maximum creep strain was. The creep strain of concrete with strength grade of C40 increased by 15.8%, 30.1%, 21.1% and 16.8% respectively on the 14th day compared with that on the 28th day at 60 d, 120 d, 180 d and 240 d. Analytical results indicated that the prediction accuracy of fib MC2010 model, ACI 209R-92 model and CEB-FIP MC90 model was better than that of other prediction models. The prediction accuracy of fib MC2010 model was the best one, the average and standard deviation were 0.992 and 0.282, respectively. The second was ACI 209R-92 model, the two values were 1.102 and 0.381, respectively. The third one was CEB-FIP MC90 model, the two values were 1.167 and 0.327, respectively. According to the results of this paper, it was suggested that, the partial safe prediction model of creep final value could be used for creep calculation of CFT eccentric compression members in the structural design.