Behaviour of Reinforced Concrete Deep Beams with Openings in the Shear Zones

Abstract

Reinforced concrete deep beams are useful in high rise buildings to support high loading in a structure. In deep beam construction, openings are usually provided in beams for accessibility purpose and to accommodate essential services such as power supply, ventilation system and network system access. However, the presence of openings in deep beams may lead to many problems in the beam behaviour such as reduction in the beam strength, cause excessive cracking and deflection. Hence, this research was conducted to study the behaviour of reinforced concrete deep beams with openings. Two openings, one in each shear span, were placed symmetrically at the top of shear span near support about the mid-point of the beam. Test parameters included the opening size and shape. The openings were circular and square in shapes. The sizes of the openings considered in this study included Æ150 mm, Æ200 mm and Æ250 mm for circular whereas the size of square shape were 150x150 mm, 200x200 mm and 250x250 mm. All the beam specimens had a cross-section of 100 mm x 500 mm and a total length of 1200 mm. The beams were tested under four-point bending until failure. The results in terms of load deflection behaviour and crack patterns were discussed. Provision of circular openings could reduce the beam capacity to a range of 30 – 35% of the original beam capacity while the inclusion of square openings caused a significant loss of beam strength, about 40 – 80% as compared to the beam capacity of the solid beam.