Study On The Time-Dependent Behavior Of Steel Fiber Reinforced High-Strength Concrete Beams With FRP Bars Under Service Condition

Normal concrete beams reinforced with FRP bars ususlly produce a larger deflection and crack width due to the property of FRP rebar, mainly lower elastic modulus. The addition of steel fiber in high-strength concrete may reduce the crack width and deflection of beams because steel fiber reinforced high-strength concrete can enhance the bond performance between concrete and rebar, resist crack developing and increase section stiffness. Existing results shown the deflection and crack width of concrete beams increase with time as a result of creep and shrink of concrete. This paper study the time-dependent behavior of steel fiber reinforced high-strength concrete beams with FRP bars under service condition, and the main contents and results are as follows:(1)Experiments on serviceability of steel fiber reinforced high-strength concrete beams with FRP bars under repeated loading after suffering long-term sustaining loading with low-lever loads were carried out. The results show that the load-deflection curves are almostly linear under low-lever repeated loading, and the deflection changes are mainly caused by the elastic deformation. And then the effect of loading level, the fraction of steel fiber by volume, the ratio of FRP rebar on the deflection and crack width of beams.(2)According to the experimental results on the time-dependent behavior of steel fiber reinforced high-strength concrete beams with FRP bars under long-term sustaining loading with higher-level loads, The influence of loading level, steel fiber volume fraction and reinforcement ratio of FRP rebars on serviceability are studied. The results show that: the time-dependent deflection multiplier decreases with increasing of loading level. the higher of steel biber volume fraction and reinforcement ration of FRP rebars, the larger of the time-dependent deflection multiplier. While, the action of reinforcement ratio of FRP rebars on the multiplier are affected by stress history.(3)Based on the test results and the effective elastic modulus theory, the influence factors on long-term behavior of steel fiber reinforced high-strength concrete beams with FRP bars are studied. The variation between long-term deflection under lower-level sustaining loads and higher-level sustaining loads are comparative analysed, and the applicability of long-term deflection calculating model provided by domestic and international codes on experimental results are discussed.(4)Based on the test results, the deflection variation regular in full loading process are summarized, and the deflection calculating model of steel fiber reinforced high-strength concrete beams with FRP bars is established.