Influence of high temperature on post-peak cyclic response of fly ash concrete under direct tension

- The cyclic tensile behavior of fly ash concrete in direct tension is studied.
- High temperature effect on the cyclic tensile response of fly ash concrete is considered.
- Strain rate effect on the cyclic tensile response of fly ash concrete is considered.
- The accumulation of residual strain is found independent of temperature effect.
- A cyclic constitutive model is proposed to describe the stress-strain relation.

Few data of uniaxial cyclic tension of concrete, especially after high temperature exposure, are available due to the difficulty of testing methods. In the paper, strain rate effect and high temperature effect being considered, uniaxial monotonic and cyclic tensile tests of fly ash concrete are performed under three strain rates and four different temperatures. Experimental results show that, with the increase of temperature, tensile strength and initial modulus decrease while peak strain increases. The envelop curve of cyclic tension coincides with the monotonic curve under the same temperature. As strain rate increases, the accumulation of residual strain increases, which is independent of the high temperature effect. By means of distinguishing between temperature damage and mechanical damage, a model of cyclic behavior of fly ash concrete is proposed. According to the analysis, the nonlinearity of unloading curve is mainly dependent on strain rates while that of reloading curve is related to the temperature. The predicted model by the analytical expressions has good agreement with test data.