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

Abstract

Concerning the structural applications of steel fiber reinforced expanded-shales lightweight concrete (SFRELC), the present study focuses on the flexural fatigue performance of SFRELC superposed beams with initial static-load cracks. Nine SFRELC superposed beams were fabricated with the SFRELC depth varying from 50% to 70% of the whole sectional depth, and the volume fraction of steel fiber ranged from 0.8% to 1.6%. The fatigue load exerted on the beams was a constant amplitude sinusoid with a frequency of 10 Hz and a fatigue characteristic value of 0.10; the upper limit was taken as the load corresponded to the maximum crack width of 0.20 mm at the barycenter of the longitudinal rebars. The results showed that with the increase of SFRELC depth and the volume fraction of steel fiber, the fatigue life of the test beams was prolonged with three altered failure modes due to the crush of conventional concrete in the compression zone and/or the fracture of the tensile rebar; the failure pattern could be more ductile by the prevention of fatigue fracture by the longitudinal tensile rebar when the volume fraction of steel fiber was 1.6% and the reduction of crack growth and concrete strain in the compression zone; the fatigue life of test beams was sensitive to the upper-limit of the fatigue load, a short fatigue life appeared from the higher stress level and larger stress amplitude of the longitudinal rebar due to the higher upper-limit of the fatigue load. The methods for predicting the stress level, the stress amplitude of the longitudinal tensile rebar, and the degenerated flexural stiffness of SFRELC superposed beams with fatigue life are proposed. With the optimal composites of the SFRELC depth ratio and the volume fraction of steel fiber, the controllable failure of reinforced SFRELC superposed beams could be a good prospect with the trend curves of fatigue flexural stiffness.

Effect of Steel Fiber Content on Shear Behavior of Reinforced Expanded-Shale Lightweight Concrete Beams with Stirrups

“…To simplify the computation, the beneficial effect of stirrups on shear cracking resistance can be considered as a reliability reserve. The same formula can be used for predicting the shear-cracking force of reinforced SFRELC beams with or without web reinforcement [10], Table 2 presents the calculated values of V cr by using Formula (9). Based on the statistical analysis, the average of ratios of test to calculation results is 1.034 with the coefficient of variation as 0.027.…”

“…The studies on the flexural behavior of reinforced SFRELC beams under static concentrated loads indicated that the cracking moment, flexural stiffness, and bearing capacity as well as ductility are effectively promoted with the increasing volume fraction of steel fibers from 0.4% to 1.6%, and the crack growth is confined with decreased spacing and width [ 6 , 7 , 8 ]. A fatigue life of reinforced SFRELC superposed beams with ductile failure mode was prolonged by preventing fatigue fracture of longitudinal tensile rebar and reducing crack growth, and the failure could be expected with the trend curves of fatigue flexural stiffness [ 9 ]. By the experimental study on shear-cracking force and shear crack extension, mid-span deflection, shear failure mode, and shear capacity, the effective enhancement of steel fibers was confirmed on the shear behavior of reinforced SFRELC beams without stirrups; however, the brittle failure could not be prevented with the rupture of expanded shales along diagonal cracks [ 10 ].…”

Advanced Structural Concrete Materials in Bridges

“…Advances in steel-fiber-reinforced concrete include the development of steel-fiberreinforced expanded-shale lightweight concrete (SFRELC) [3]. In particular, the authors explored the fatigue strength of composite SFRELC-RC beams through experiments.…”

Advanced Structural Concrete Materials in Bridges

“…Advances in steel-fiber-reinforced concrete include the development of steel-fiber-reinforced expanded-shale lightweight concrete (SFRELC) [ 3 ]. In particular, the authors explored the fatigue strength of composite SFRELC-RC beams through experiments.…”