Polytechnic (Dec 2023)
Strengthening of Reinforced Concrete Beams with Transverse Circular Openings Using Near Surface Mounting Steel Bars
Abstract
This study investigated the effectiveness of using near-surface mounted (NSM) steel bars to restore the shear strength of deep beams and deal with the presence of openings in slender beams. fourteen simply supported reinforced concrete beams were tested with varying shear span-to-depth ratios (a/h) of 1.5 and 3.61, divided into two groups, and subjected to a two-point load configuration. Some beams had openings at different positions, classified as large or small with opening height ratios (ho/h) of 0.4 and 0.2, respectively. In the second group, six specimens were reinforced with nsm steel bars in three stirrup configurations (square, diamond, and parallelogram) surrounding the openings. All specimens had a crosssection size of 100 mm £ 150 mm and a total length of 2000 mm. The results of the test indicated that having openings in the beams led to reductions in ultimate load capacity for different beam types. Specimens reinforced with diamond stirrup bars showed an increase in ultimate load capacity of up to 33.1%, while those with square and parallelogram stirrup bars improved by up to 21.5% and 26.5%, respectively. Minor variations in bar diameter had slight effects on ultimate load capacity, resulting in a 10% increase for the parallelogram scheme and 7% for the square scheme. The reductions in ultimate load capacity due to openings were 45 % for large circular openings in the shear zone of deep beams, 18.7 % for large circular openings in slender beams subjected to shear, 14.6 % for large circular openings affecting both shear and flexural behavior and 19.5 % for small openings impacting shear and flexural behavior in slender beams.
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