Strength enhancement in deep beams with engineered web openings via diagonal struts

Regarding provision of service openings in RC deep beams, the approach of researchers so far has been to predefine the shape and size (area) of opening and impose it upon the member. As a result, the beam wherein the opening interfered with the internal load path used to suffer loss of strength depending on the extent of such interference. On the contrary, this study aims to demonstrate that openings suitably configured to ensure optimum width to the interior diagonal struts can increase the member strength via enhancement of strength of the diagonal struts without incurring higher beam soffit deflection. Simply supported single-point centrally loaded RC deep beams with a variety of openings were numerically examined and experimentally tested to decide an opening configuration that would enhance the strength of the two interior struts. Among the different openings investigated, beams with star opening proved to be the best by resisting an average normalized experimental peak load of 432 kN with a beam soffit deflection of 1.21 mm, as against 377 kN and 1.79 mm in case of solid beams, respectively, suggesting that an ideal opening configuration from strength point of view should follow the profile of the interior struts. Accordingly, a parametric numerical analysis was carried out with a simple triangular opening system from which it was concluded that openings ensuring an aspect ratio of about 2–3 for the diagonal struts would considerably enhance the strut strength and therefore the beam strength, without incurring higher beam soffit deflection. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.