Torsional strength evaluation of reinforced SCC box beams strengthened internally by opened and closed transverse concrete diaphragms

Faculty of Engineering, Al-Mustansiriayah University, Baghdad, Iraq.

^* Corresponding author: alihaziz@uomustansiriyah.edu.iq

Abstract

There are a few researches about box (hollow core) RC beams under the effect of torque moment; therefore, a torsional failure mechanism is not understood well. In the present paper, the concept (technique) of adding internal concrete diaphragms, in transverse direction, is adopted. Six self-compacting concrete beam specimens having a dimension of (2200x220x350mm) for length, width and height, respectively were poured and tested. Three variables are adopted in the present study, section type, number and type of the internal diaphragms. Experimental results show that the ultimate torque moment increases about (43%-61%) and (89%-94%) for beam specimens strengthened internally by two and four diaphragms respectively. Also, increasing internal diaphragms from two to four, led to increase the ultimate torque moment about (33%-46%). Furthermore, the change of section from box section with four internal diaphragms to solid section, led to increase in ultimate torque moment about (28%-33%). The paper concludes that the increase in torsional capacity is attainable for box (hollow core) beams by using the technique of strengthening by internal diaphragms; Also, the box sections can be made with internal opened diaphragms and possess same capacity or contribution of the closed ones.