This paper aims to experimentally and numerically study the effect of steel fiber on the behavior of Lightweight
Foamed Reinforced Concrete (LWFRC) deep beams and its mechanism to improve the mechanical properties and
crack control of concrete. In addition to this, steel fibers compensate for the lack of resistance due to the use of
lightweight foamed concrete (LWFC). This paper will also address the effect of some variable parameters on the
structural behavior such as: (1) volume of fiber; (2) fiber aspect ratio; (3) longitudinal reinforcement ratio.
The experimental program consists of four groups; each group comprises two beams compared to the control
specimen. All beams have an overall depth of 800 mm, width of 150 mm, and total length of 2200 mm with span
of 2000 mm. Tests were performed under two points load with constant shear-span to depth ratio equal to one.
The used LWFC has an average cubic, cylindrical compressive strength and splitting tensile strength of 33, 28
and 3.10 MPa, respectively. Hooked end steel fibers with length 40, 50, and 60 mm and 0.8 mm diameter were
used with 0%, 0.5%, 0.75% and 1.0% volumetric ratio.
The obtained results indicated that the cracking and the ultimate load has increased by 18.5% and 25.5%, respectively due to use steel fibers. Furthermore, the displacement ductility and toughness has increased by 38%
and 56%, respectively. The failure mode of LWFRC deep beams is shear brittle failure.
Shear capacity of all deep beams based on ECP 203–2017 (ECP-203, 2017) is calculated and compared with
that from ACI 318–19 (ACI 318-19, 2018) which is based on strut and tie model (STM). Comparing the experimental results with STM results showed that ECP 203–2017 (ECP-203, 201) is slightly conservative in calculating
the ultimate capacity than ACI 318–19 (ACI 318-19, 2018) for the range of the studied variables in this research
and not in general. Finally, as the STMs are debatable, ANSYS 15 software was used to numerically study the behavior of LWFRC deep beams. Verification of numerical models has been done by comparing the results of the
load deflection curves, cracks and ultimate loads with the experimental ones. |
