Abstract
In this paper, an investigation on the behaviour of RC beams with circular openings in the flexural zone and shear zone strengthened using steel plates is presented. Totally seven beams were cast: a control beam, one beam with a circular opening of size of one-third the depth of the beam (100 mmϕ) in the flexural zone, one beam with opening strengthened using the steel plate, one beam with a circular opening of size of 100 mmϕ in the shear zone, one beam with an opening in the shear zone strengthened using the steel plate, one beam with two circular openings of size of 100 mmϕ in the shear zone, and another beam with two openings in the shear zone strengthened using the steel plate. The experiments were conducted in a loading frame of 400 kN capacity. The beams were subjected to two-point loading. The ultimate load carrying capacity reduced marginally by 1.78% and 2.8% compared to that of the control beam when a circular opening of 100 mmϕ was provided in the flexural zone and shear zone, respectively, and when the opening was strengthened with steel plates, it reduced by 3.04% and 25%, respectively, but the ductility increased when steel plates were provided. Beams with an opening of size of one-third the depth of the beam (100 mmϕ) in the flexural zone strengthened with the steel plate can be provided, as the load carrying capacity is only marginally reduced compared to the control beam, and the ductility is more when compared with beams with unstrengthened openings.
Highlights
In high-rise framed structures, providing service ducts is necessary for various purposes
Can play a key part in reinforcing and strengthening the structures. e reinforced concrete beams with openings can be strengthened by CFRP sheets, GFRP sheets, laminates, rods, fabrics, and so forth with different strengthening schemes. e load carrying capacity of the reinforced concrete beams with openings increases when strengthened externally with CFRP sheets in RC T-section deep beams [1], fibre reinforced polymer sheets in RC beams [2], unidirectional CFRP fabrics in RC T-beams [3], and NSM GFRP rods saturated with epoxy in RC self-compacting concrete deep beams [4]
A new method has been developed for strengthening the RC beams with circular openings in the flexural zone and shear zone using steel plates connected using shear connectors around the openings placed during casting of the beam. e use of steel plates around the openings for strengthening the RC beams with circular openings has not been reported so far. e outcome of this work represents promising data for further studies to be conducted in large scale to improve the load capacity of the RC beams with openings in construction works
Summary
In high-rise framed structures, providing service ducts is necessary for various purposes. A relatively thin reinforced U-shaped concrete jacket made of self-compacting concrete to repair the shear damaged RC beams restores the load carrying capacity with respect to the initial samples, enhances the overall structural performance, and alters their failure mode to a more ductile one. A new retrofitting technique to upgrade the structural behaviour of shear-critical rectangular and T-shaped reinforced concrete (RC) deep beams without steel stirrups using CFRP ropes as shear reinforcement exhibits increased capacity and significant improvement in the overall behaviour compared to the control beams. E repair of heavily damaged shear-critical reinforced concrete beams jacketed with mild steel small diameter U-shaped transverse stirrups examined experimentally in thin, U-shaped cement mortar jacketing showed reduced brittleness and increased deflections at failure up to six times compared to the initially tested specimens and can alter the failure mode from brittle shear to ductile flexural under certain circumstances [22]. A new method has been developed for strengthening the RC beams with circular openings in the flexural zone and shear zone using steel plates connected using shear connectors around the openings placed during casting of the beam. e use of steel plates around the openings for strengthening the RC beams with circular openings has not been reported so far. e outcome of this work represents promising data for further studies to be conducted in large scale to improve the load capacity of the RC beams with openings in construction works
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