Abstract
In this study, the effect of fire flame on the punching shear strength of steel fiber reinforced concrete flat plates was experimentally investigated using nine half-scale specimens with dimensions of 1500×1500 mm and a total thickness of 100 mm. The main investigated variables comprised the steel fiber volume fraction 0, 1, and 1.5% and the burning steady state temperature 500 and 600 °C. The specimens were divided into three groups, each group consists of three specimens. The specimens in the first group were tested with no fire effect to be the reference specimens, while the others of the second and third groups were tested after being exposed to fire-flame effect. The adopted characteristics of the fire test were; (one hour) burning time duration and 500 and 600 °C steady state temperature with sudden cooling process (water sprinkling directly after burning). The test results proved that exposing to direct fire effect for one hour caused a reduction in the punching shear strength with an increase in the ultimate mid-span deflection. Also, it was noticed that using steel fiber in the concrete mix leads to a significant increase in the punching shear strength for both the unburned and burned specimens. The ultimate punching load increased by about 11 and 16.6% for the unburned specimens with 1.0 and 1.5% steel fiber volume fraction, respectively, and by about 22.4 and 19% for the burned specimens at 500 °C with 1.0 and 1.5% steel fiber volume fraction, respectively. While, it was increased by about 29.2 and 21.5% for the burned specimens at 600 °C with 1.0 and 1.5% steel fiber volume fraction, respectively, as compared with the reference specimen of each group. Doi: 10.28991/cej-2021-03091751 Full Text: PDF
Highlights
A flat plate is a reinforced concrete floor which is usually with or without drops, supported generally without beams or girders [1]
The main goal of this study is to investigate experimentally the effect of adding steel fibers on the punching shear strength of the flat plates exposed to fire where, it is expected that the addition of fiber in concrete mix leads to an increase in the compressive and tensile strength and it is can reduce spalling and enhance concrete resistance at fire
The steel fiber ratio 1% by volume fraction was more sufficient than the ratio 1.5% in both burning temperatures 500 and 600°C since the ratio 1.5% resulted in a great reduction in the compressive and tensile strengths of concrete than that in the ratio 1% due to the effect of the expansion damage for the steel fiber which was greater in amount in the ratio 1.5% than that’s in the ratio 1%
Summary
A flat plate is a reinforced concrete floor which is usually with or without drops, supported generally without beams or girders [1]. Reinforced concrete flat plates are chosen by architects and engineers because they provide an elegant form of construction. They simplify and speed up site operation, allow easy and flexible partitioning of space and reduce the overall height of building [2]. Concrete and steel undergo a reduction in their properties such as the strength, stiffness and physical properties [4, 5] Some of these properties cannot recoverable after cooling, the punching strength of flat slabs subjected to fire is expected to be significantly affected [6]. The main goal of this study is to investigate experimentally the effect of adding steel fibers on the punching shear strength of the flat plates exposed to fire where, it is expected that the addition of fiber in concrete mix leads to an increase in the compressive and tensile strength and it is can reduce spalling and enhance concrete resistance at fire
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