Openings Effect on the Performance of Reinforced Concrete Beams Loaded in Bending and Shear

Abstract

Transverse openings are often provided to reinforced concrete beams to accommodate utility ducts and pipes. This technique is usually adopted to avoid the creation of dead space in structures caused by extended dropped ceilings and leads to significant cost saving. On the other hand, the provision of openings through a beam creates a reduction in its strength and affects serviceability. In this study, ten reinforced concrete beams were cast using C30 concrete. Material characterization and engineering properties tests were carried out to ensure compliance with the requirements provided by the codes of practice. The effect of vertical positioning and size of openings was investigated through subjecting the beams to a four-point bending test after 28 days of curing. Maximum load capacity, first cracking load, and deflections at mid-span were recorded and crack pattern and failure mode were evaluated. Test data showed that openings of depth greater than 0.4d significantly affect the beams’ strength and lead to earlier cracking, while the failure mode remains essentially the same, a diagonal tension crack through the opening except for opening of 0.5d size where the failure occurred by a sudden formation of two independent shear cracks above and below the opening. When holes were located above the centroid of the section, the beams exhibited a lesser deflection characterized by the absence of plastic deformation. Furthermore, a significant reduction in strength was recorded compared to cases where the positioning of openings was in tension chords. This was validated using equations from the ACI code of reinforced concrete design.

Simplified shear equation of deep concrete beam considering orientation effect of opening and mechanical properties of fibre-concrete interface

“…The shear capacity in the normal beam is limited to an opening height of less than 0.25 of the overall beam depth [ 45 , 46 ]. However, in a deep beam, both the height and length of the opening influence the load capacity of the section.…”

Reinforcement methods of an reinforced concrete beam with the circular opening in the plastic hinge region under cyclic loading

“…In recent years, for an RC residential building structure, designers have frequently encountered the problem of a transverse opening in the plastic hinge region of a beam member due to actual pipeline configuration requirements. Recent studies have been conducted on the behavior of simply supported RC beams with transverse opening (Ame et al, 2020;Amiri et al, 2011;Chiu et al, 2023;Ling et al, 2020), some researchers have also reported the use of FRP to strengthen the transverse opening region (Aksoylu et al, 2020;Morsya and Barima, 2019;Özkılıç et al, 2022). However, very little research on a transverse opening in the plastic hinge region of an RC beam has been performed.…”

Behavior of Reinforced Concrete Beams with Vertically Penetrated Holes across the Cross ‐ Sectional Depth

“…In practice, a network of ducts and pipes is needed to accommodate utilities like sewage, power, air conditioning, telephone, and water supply [1]. Accordingly, most of the Reinforced Concrete (RC) structures in Iraq contain holes in RC beams, commonly known as penetrations or openings, which are created to accommodate the passage of piping or other utilities [2].…”