Mechanics, Materials Science & Engineering, December 2016
ISSN 2412-5954
The Evaluation of Torsional Strength in Reinforced Concrete Beam9 Mohammad Rashidi1, Hana Takhtfiroozeh2 1 Department of Civil Engineering, Sharif University of Technology, Tehran, Iran 2 Department of Civil Engineering, Building and Housing Research Center, Tehran, Iran DOI 10.13140/RG.2.2.16568.75521
Keywords: torsional strength, concrete beam, transverse and longitudinal bars, reinforcement.
ABSTRACT. Many structural elements in building and bridge construction are subjected to significant torsional moments that affect the design. A simple experiment for the evaluation of the torsional strength of reinforced concrete beams as a one of this structural elements is presented in this research. The objective of this experiments would be the role of transverse and longitudinal reinforcement on torsion strength. Four beam test samples has been tested with the same length and concrete mix design. Due to the fact, that the goal of this experiment is to determine the effect of reinforcement type on torsion strength of concrete beams; therefore, bars with different types in each beam have been applied. It was observed that the ductility factor increases with increasing percentage reinforcement from the test results. It should be also noted that transverse bars or longitudinal bars lonely would not able to increase the torsional strength of RC beams and both of them can be essential for having a good torsional behaviour in reinforced concrete beams.
Introduction. The interest in gaining better understanding of the torsional behaviour of reinforced concrete (RC) members has grown in the past decades. This may be due to the increasing use of structural members in which torsion is a central feature of behaviour such as curved bridge girders and helical slabs. The achievements, however, have not been as much as those made in the areas of not contain the more elaborate techniques. Predictions of current standards for the ultimate torsional capacity of RC beams are found to be either too conservative or slightly risky for certain geometry, dimensions and steel bar sizes and arrangements. Torsional moments in reinforced concrete are typically accompanied by bending moments and shearing forces. However, simplified methods in design codes are based on a simple combination of the pure shear methods and pure torsion methods. In the ACI code [1], the effects of the torsional moment are accounted for by superimposing the amount of transverse and longitudinal steel and the intensity of the shearing stresses required for torsion resistance to those required for shear resistance. The Canadian code [2] assumes a similar interaction and further superimposes the effects of torsion and shear on the longitudinal strain indicator required in the design solution. Moreover, interaction surfaces between shearing and axial forces and bending moment such as those suggested by Elfren et al. [3] and Ewida and McMullen [4] are still of practical importance. The use of such interaction surfaces and the use and development of the code equations require knowledge of the pure torsional strength of reinforced concrete. Rahal and Collins [5] assigned the methods available for computing the torsional capacities to two main categories. Methods in the first category use semi-empirical equations chosen to fit available experimental data. The strength of these methods comes generally from their simplicity. Methods in the second category use procedures based on more rational models such as the space truss model. These models are generally more time demanding, but their strength comes from their 9
The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/
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