Response of reinforced concrete beams with multiple web openings to static load

Web openings in beams occur quite often in practice to provide convenient passage of electrical and mechanical ducts. Shear failure may dominate in cases where web opening created or the flexural strength has been increased. In such cases, increasing the shear capacity can prevent catastrophic shear failure. In this paper, the investigation of the response of simply supported reinforced concrete T-beams with multiple web circular openings is presented. An experimental research program was conducted on the shear behavior of simply supported beams subjected to an incremental concentrated static load at mid span. Seven reinforced concrete T-beams were tested with two design parameters, including number of web circular openings (four or six) and the method which was used to strengthen the member at openings (using internal deformed steel bars as in the case of the openings are planned before casting the beams or using carbon fiber reinforced polymer (CFRP) fabric as in the case of the openings will be created in the existing beams). Test results indicated that the strengthening of beams at openings may compensate the decrease of the beam capacity due to the existence of the openings under static loading. The compensation of the beam capacity depends on the strengthening method which was adopted. The gain in shear capacity of the tested beams ranged between 27% and 92% which also represents about 86% to 114% of the reference solid beam capacity under static loading. A nonlinear finite element program, ANSYS 12.1 release, was used to validate the results of the tested beams. Comparisons between the finite element predictions and experimental results in terms of failure loads and load-deflection relationships are presented and showed good agreement.