Model for estimating the flexural performance of concrete reinforced with hooked end steel fibers using three‐point bending tests

Abstract

The behavior of fiber reinforced concrete (FRC) depends on the characteristics of both the concrete matrix and fibers. Previous studies have concluded that the number of hooked ends increases the contribution of steel fibers to the tensile performance of concrete. ACI 318 code, MC10 fib code and RILEM TC 162‐TDF standard permit the use of steel fiber reinforced concrete (SFRC) for example, the minimum shear reinforcement made of deformed steel bars in flexure‐controlled elements. Other investigations have demonstrated the suitable performance of SFRC in shear‐controlled members and for seismic rehabilitation applications. It has become apparent that the adequate use of SFRC depends on the knowledge and prediction capabilities of its tensile performance. The results of three‐point bending tests on SFRC beams using the test procedure established by the European standard EN‐14651 are presented and discussed herein. Tests were executed with 20 standardized beams made of concrete with a nominal compressive strength of 24 MPa and hooked end steel fibers with an aspect ratio of 65 were applied. Variables were the fiber dosage (0, 20, 40, 60 kg/m3) and the number of fiber hooked ends (1, 1.5, and 2). A numerical model aimed at estimating the residual flexural tensile strength of the SFRC is developed. The proposed model was calibrated using a database of 256 tests, 20 from this study and the remaining 236 from 15 other studies.

Empirical equations for flexural residual strengths in concrete with low volumetric fractions of hook‐end steel fiber

“…While the failure of steel fiber in the matrix occurs solely by slippage, the fiber length ( l f ) is usually less than the critical length required 2 to develop the maximum tensile strength of the fiber, according to Abdallah et al 35 increasing the embedded length of the 3D fibers did not result in an improvement on the maximum pull‐out load, but increase in the total pull‐out work, and also due to the loss of adhesion with the crack openings. Figure 7A reveals that the failure occurs in steel, the tensile strength of fibers influences the failure mode of the fiber that is being extracted from a concrete matrix 19,36 . The effect of the fiber volume reveals a difference in the order of 10 3 compared to the maximum stress (Figure 7B) of Equation (4).…”

“…Figure 7A reveals that the failure occurs in steel, the tensile strength of fibers influences the failure mode of the fiber that is being extracted from a concrete matrix. 19,36 0.00…”

“…The equations include the most significant parameters governing the tensile behavior of SFRC, tensile stress at failure pull-out and fiber content. Parameters as inclination, 16,17 the number of hooked ends, 18,13,19 and random distribution 1 of steel fibers were not considered.…”

“…The equations include the most significant parameters governing the tensile behavior of SFRC, tensile stress at failure pull‐out and fiber content. Parameters as inclination, 16,17 the number of hooked ends, 18,13,19 and random distribution 1 of steel fibers were not considered. To further prove the model's effectiveness, a comparison with the other models found in the literature and described above is also reported at the end of the article.…”