Study On Creep Of Concrete Filled Steel Tubular Members Based On B3 Model

In this paper, concrete creep model B3 based on solidification theory is introduced into creep calculation of Concrete Filled Steel Tubular (CFST) members. With analysis of mechanical characteristics of CFST beam-column and beam members, a creep model of CFST members that agrees with microcosmic mechanisms and characteristics of concrete creep is proposed. Afterwards, B3 model is substituted for ACI, CEBFIP, GL2000 model and elastic continuation and plastic flow theory to form 4 new models. Calculation results of all the models are compared with experimental data, drawing with the conclusion that creep model of CFST members based on B3 model is more reasonable and accurate than other models.Since the influence of concrete mix proportion on concrete creep has been taken into account in B3 model, using the proposed model, effects of several internal factors that are considered to have impact on CFST creep, such as water to cement ratio( w/c) and aggregate to cement ratio(a/c) of concrete, are firstly investigated in the paper, concluding that creep of CFST members rise as the increase of water to cement ratio but fall of aggregate to cement ratio. Besides, some of the external factors are discussed further, including steel ratio, eccentricity ratio, axial load, and loading age. It is shown that external factors have dramatic influence on CFST creep, which should be calculated in practice.