The Research Of Properties For Creep Of Axial Compression Fly Ash Concrete-filled Steel Tubular Members

The comprehensive utilization of fly ash has a significant effect on conservation of energy and natural resources, especially on concrete materials in the civil engineering. Fly ash contributes a lot to the mechanical property of concrete as well as the long-term performance, which conforms to the concept of sustainable development with civil engineering. As one of the important indexes of the long-term performance of concrete, creep has been highly valued and close attention by scholars and engineers at home and abord. Creep affects the force and deformation of concrete-filled steel tube (CFT) structure deeply. Plenty of studies have been made on this problem of CFT structures, but the issues of creep about fly ash concrete-filled steel tube (FACFT) little have been published. Therefore, it's necessary to research on the problems systematically.This paper makes research on the creep of FACFT under axial forces by theoretical analysis combined with experiments. In theory, multi-scale thought was used to build cluster model for creep of fly ash concrete sealed. This model divides fly ash concrete to aggregate and mortar. Creep mechanism was studied through microstructure combined with macro-phenomenon. The hydration of mortar in fly ash concrete are virtual for limited cluster units formed gradually, and the clusters coming into being met the stress-strain coordinating relation with aggregate. Cluster units is the Nishihara Model in rheology, it can describe mortar constitutive relationship well. The parameters in this model were got from regression of test dada.Secondly, cluster model for creep of fly ash concrete sealed was introduced into the existed calculating model of creep of CFT under axial compress to calculate the creep strain of FACFT, the results and experimental data were contrast analyses.And compared the predicted creep strain of 300 days using this model, ACI209R model, CEBFIP90 model and B3 model.Finally, the software ANSYS was used to simulate the experiments. The obtained results are in good agreement with the experimental data.