Experimental Investigation on the Effect of Steel Fibers on the Flexural Behavior and Ductility of High-Strength Concrete Hollow Beams

Ahmmad Abbass,Mustafa Özakça,Sallal Abid

doi:10.1155/2019/8390345

Ahmmad Abbass, Mustafa Özakça + Show 1 more

Open Access

https://doi.org/10.1155/2019/8390345

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Abstract

In this study, an experimental work was directed toward comparing the flexural behavior of solid and hollow steel fiber-reinforced concrete beams. For this purpose, eight square cross-sectional beam specimens, four solid and four hollow, were prepared. One concrete mixture with four different steel fiber contents of 0, 0.5, 1.0, and 1.5% were used. The side length of the central square hole was 80 mm, whereas the cross-sectional side length was 150 mm. All beams were tested under four-point monotonic loading until failure. In addition to the solid and hollow beams, cylinders were cast to evaluate the compressive strength, splitting tensile strength, and modulus of elasticity, whereas prisms were used to conduct the fracture test. The test results showed that all fibrous beams failed in flexure, whereas those without fiber exhibited flexural-shear failure. In general, the flexural behavior of fibrous-beams was superior to that of beams without fiber. The hollow beams with fiber contents of 0, 0.5, and 1.0% were observed to withstand lower loads at cracking, yielding, and peak stages compared with their corresponding solid beams; this was not the case for the 1.5% fiber hollow beam, which exhibited a higher peak load than its corresponding solid beam. Although all eight beams exhibited ductility indices higher than 3.7, hollow beams exhibited better ductility than solid beams, showing higher ductility index values.

Highlights

With the quick and huge development of the construction industry across the world, the demand for concrete has increased significantly over the last two decades. is is attributed to the attractive characteristics of concrete, including its high compression capacity, the availability of its constituents, and the ease of its production, in addition to the production cost, which is moderately satisfactory for such developments
E flexural test curves of the tested prisms with the four different fiber contents are shown in Figures 5 and 6. e load-displacement curves of the tested prisms are shown in Figure 5, whereas Figure 6 presents the relationship between load and the crack mouth opening displacement (CMOD)
All solid fibrous beams failed in flexure, whereas those without fiber exhibited less ductile behavior and failed in flexural-shear cracking. e nominal flexural capacity (Mn) of the steel fiber reinforced concrete (SFRC) beam is the resultant from the contributions of both reinforcing bars (m1) and the residual tensile strength produced from fiber bridging (m2). e ACI 544 [44] proposed the following equation for the calculation of the flexural capacity of singly reinforced fibrous concrete solid beams: Mn m1 + m2, (3)

Summary

Introduction

With the quick and huge development of the construction industry across the world, the demand for concrete has increased significantly over the last two decades. is is attributed to the attractive characteristics of concrete, including its high compression capacity, the availability of its constituents, and the ease of its production, in addition to the production cost, which is moderately satisfactory for such developments. The reduction in section means lower moment of inertia, which may lead to lower strength and higher deformations, the use of steel fibers is known to increase the flexural strength and enhance the flexural behavior of reinforced concrete beams This positive contribution may substitute the reduction in strength and performance resulting from the reduction of the section size of hollow beams compared with solid ones. Trying to fill some gaps of knowledge about this issue, in this study, an experimental work was directed toward investigating the flexural performance of high-strength steel fiber-reinforced hollow concrete beams For this purpose, a square central longitudinal hole was used to reduce the cross-sectional area by approximately 28% and steel fiber contents up to 117 kg/m3 were incorporated in the concrete mixtures

Experimental Work

Test Results of the Reinforced Solid and Hollow Beams

Conclusions