Deformation calculation of ultra-high toughness cementitious composite–concrete beam under flexure fatigue with ultra-high toughness cementitious composite fatigue damage model

Ultra-high toughness cementitious composite is a construction material, with the characteristics of strain hardening and multiple cracking under uniaxial tension. It can be applied as a feasible repair material for structures subjected to fatigue load. In this paper, flexural fatigue tests on the composite beam constituted of an ultra-high toughness cementitious composite layer and a concrete layer with the same height (ultra-high toughness cementitious composite–concrete beam) are carried out. Then, on the basis of fatigue stress degradation models of concrete and ultra-high toughness cementitious composite, the fatigue process of ultra-high toughness cementitious composite–concrete beam is analyzed. It is shown that, the fatigue failure of ultra-high toughness cementitious composite–concrete beam in this paper is caused by the damage of ultra-high toughness cementitious composite layer. Therefore, with the flexural fatigue damage model of plain ultra-high toughness cementitious composite beam, the evolution curve of maximum tensile strain on the bottom surface of ultra-high toughness cementitious composite layer with the ratio of load cycles is calculated. The calculated strain is in good agreement with the experimental result. That is to say, the factual deformation, dependent on the fatigue stress level, can be predicted by the calculated result. As a result, the flexural fatigue damage model of ultra-high toughness cementitious composite can be applicable to evaluate the fatigue performance of ultra-high toughness cementitious composite–concrete beam.