Effects of square openings in reinforced concrete deep beams

Reinforced concrete (RC) deep beams are usually used in tall buildings' or
offshore structures. The presence of web opening in such beams can often be necessary
to accommodate crucial services, for instance ventilating as well as air conditioning
ducts. This research was conducted to study the effects of opening in RC deep beams
with various sizes of Openings as a test parameter. The shape of choice is square
opening. The square openings were placed at the top of shear span near support. A total
six deep beams with same dimensions (100 mm x 500 mm)and the total length of 1200
mm were cast. Three control deep beams and the remaining deep beam with openings
with size of 150x150 mm, 200x200 mm and 250x250 mm were studied. The beams
were tested to failure under 4-point bending. The results obtained from the test
including load-deflection behaviour, and crack pattern. The reinforced concrete deep
beams with openings develop shear-diagonal cracks at the openings corner, due to the
stress concentration at sharp edges.. The crack pattern development varies with opening
sizes. The cracking development increased as the size of openings increased. The
presence of openings in RC deep beams caused significant reduction in the beam
strength. As compared to solid deep beam, the reduction of beam strength falls in the
range of 43% - 82%. As for RC deep beams with openings, losses in beam capacity
about 43%,
51%, and 82% in beam DBS1, DBS2, and DBS3, respectively were
obtained. The size of opening plays a crucial part in this study. The larger the opening
size, the more severe crack pattern was observed.