EXPERIMENTAL STUDY ON BENDING FATIGUE DAMAGE AND STRAIN DEVELOPMENT OF RC BEAM STRENGTHENED WITH TRC

Four-point bending loading test was carried out to study the influence of reinforcement forms, reinforcement ratios of TRC and steel bars, and damage degree of beams on fatigue life, destructive process and strain development of beams reinforced with TRC. The results show that the destructive process of reinforced beams can be divided into three stages. At the first stage,at approximately 40000 cycles, new cracks appear,and at the end of this stage no new cracks shows up, this stage is short compared with the whole process. At the second stage, the deflection of beams has almost no increment, and at the end of this stage, more new cracks appear and the main crack forms. At the third stage, the mid-span deflection of beams rapidly increases, and the fatigue failure occurs in a short time. The compressive strain of concrete and the tensile strain of steel bars also have three development stages: beginning development stage, stable development stage, and rapid development stage. The increase of reinforcement ratios of TRC and steel bars can improve the fatigue life of beams through slowing down the rising speed of neutral axis and reducing the concrete compression strain of fatigue failure. The larger damage induced by static load results in the earlier arrival of the third stage of the reinforced beam and reduces the fatigue life of reinforced beams.