Fatigue Behavior of Steel Fiber Reinforced High-Strength Concrete under Different Stress Levels

Abstract

View the article online for updates and enhancements. Abstract. The investigation was conducted to study the fatigue behavior of steel fiber reinforced high-strength concrete (SFRHSC) beams. A series of 5 SFRHSC beams was conducted flexural fatigue tests at different stress level of 0.5, 0.55, 0.6, 0.7 and 0.8 respectively. Static test was conducted to determine the ultimate static capacity prior to fatigue tests. Fatigue modes and S-N curves were analyzed. Besides, two fatige life prediction model were analyzed and compared. It was found that stress level significantly influenced the fatigue life of SFRHSC beams and the fatigue behavior of SFRHSC beams was mainly determined by the tensile reinforcement. IntroductionIn practical engineering, a large number of structures such as bridge decks, offshore installations and airport runaways often bear cyclic loads. These loads such as wind loads, and wave loads could result in progressive and continuous micro cracks, which leads to the increased permanent strains and decreased stiffness of the structure. The fatigue failure will eventually occur by the damage. Therefore, considerable interest has been developed on the fatigue performance of the concrete structures. The mechanism of fatigue in concrete can be divided into three distinct stages. The first stage is termed as flaw initiation and involves flaws forming within weak regions of the concrete. The second stage is known as micro cracking and is featured by slow growth of flaws to a critical size. The third stage occurs when a continuous macro cracks form, eventually leading up to the final failure [1]. The first and third stage make up approximately 10% of the total curve separately, while the second stage accounts for the remaining 80% [2]. The addition of fiber reinforcing can increase the fatigue performance of the concrete under flexural fatigue loading and explained that the fibers would be able to bridge cracks and prolong fatigue life under tensile forces [3]. The effects of the fiber content, fiber aspect ratio and notchto-depth ratio on the concrete fracture and fatigue behaviour were studied, and the fatigue strengths of SFRC beams were calculated. According to the regression technique, some empirical formulas for predicting the fatigue strength of SFRC beams were also suggested [4]. 11 beams reinforced by a new kind of steel (20 MN Siv) under static loading and fatigue loading with constant amplitudes were tested and the calculation method of concrete strain on the edge of compressive zone and the tensile stress of longitudinal reinforcements was put forward [5]. Fatigue test of RC beams was conducted, and the conclusion was that the mode of failure was related with stress level. In low stress level, fatigue specimens broke in the mode of bending failure with the sign of brittle fracture of reinforcement, and in

Flexural Fatigue Performance of Steel Fiber Reinforced Expanded-Shales Lightweight Concrete Superposed Beams with Initial Static-Load Cracks

“…On the design premise of the tested reinforced SFRELC superposed beams that failed with certain flexural ductility under static loading [23,41], the typical fatigue response with three stages divided into the fast first and rapid third stages accompanied with a second steady stage for the compressive strain of conventional concrete provides the foundation for the flexural fatigue performance of the reinforced SFRELC superposed beams [30,41]. In fact, a similar fatigue response with three stages are presented for the SFRC and steel fiber reinforced lightweight concrete in compression [27,28,29], the SFRC in flexure [35,36], and the steel bars in tension [31]. Therefore, the good properties of materials are the basis for good performances of structural members.…”

“…Normally, the relationship of stress level and fatigue life is represented by the S - N curve as follows [28], S=a+blogN, where a and b are the coefficients dependent on test data.…”

“…This raises an important topic of research on the normal serviceability and reliability of engineering concrete structures under fatigue actions. Normally, the key points are concerned with the fatigue behaviors of structural materials, including the fatigue compressive performance of concrete and the fatigue fracture of tensile rebars [27,28,29,30,31]. At the level of structural members under fatigue load, geometric shapes, sectional composites of concrete and reinforcement, and the sectional stress distribution with different fatigue characteristics are also main factors [32,33,34,35,36,37,38,39,40].…”