Shear Response of Recycled Aggregates Concrete Deep Beams Containing Steel Fibers and Web Openings

Abstract

Replacement of natural aggregates (NAs) with recycled concrete aggregates (RCAs) in complex reinforced concrete (RC) structural elements, such as deep beams with openings, supports environmental sustainability in the construction industry. This research investigates the shear response of RC deep beams with openings made with 100% RCAs. It also examines the effectiveness of using steel fibers as a replacement to the minimum conventional steel stirrups in RCA-based deep beams with web openings. A total of seven RC deep beams with a shear span-to-depth ratio (a/h) of 0.8 were constructed and tested. A circular opening with an opening height-to-depth ratio (h0/h) of 0.3 was placed in the middle of each shear span. Test parameters included the type of the coarse aggregate (NAs and RCAs), steel fiber volume fraction (vf = 1, 2, and 3%), and presence of the minimum conventional steel stirrups. The deep beam specimens with web openings made with 100% RCAs exhibited 13 to 18% reductions in the shear capacity relative to those of their counterparts made with NAs. The inclusion of conventional steel stirrups in RC deep beams with openings was less effective in improving the shear response when 100% RCAs was used. The addition of steel fibers remarkably improved the shear response of the tested RCA-based beams. The gain in the shear capacity of the RCA-based beams caused by the inclusion of steel fibers was in the range of 39 to 84%, whereas the use of conventional steel stirrups resulted in 18% strength gain. The use of 1% steel fiber volume fraction in the RCA-based beam with openings without steel stirrups was sufficient to restore 96% of the original shear capacity of the NA-based beam with conventional steel stirrups. The shear capacities obtained from the tests were compared with predictions of published analytical models. The predicted-to-measured shear capacity was in the range of 0.71 to 1.49.

Effects of the Concrete Strength and FRP Reinforcement Type on the Non-Linear Behavior of Concrete Deep Beams

“…The application of deep-reinforced concrete beams in the construction sector has drawn the attention of many researchers and members of the construction industries, because this type of beam has been widely used to improve the performance of high-rise buildings, offshore structures, shear walls, and bridges due to its high shear resistance [1][2][3]. However, it may cause steel reinforcement rebars to corrode if the beam is exposed to harsh environmental conditions.…”

Numerical Modeling of Concrete Deep Beams Made with Recycled Aggregates and Steel Fibers

“…Predictions of the FE deep beam models are compared with those obtained from experimental tests conducted previously by the authors [27,28] for validation.…”

“…Fourteen FE models were developed for large-scale RC deep beams tested previously by the authors [27,28]. A summary of the deep beam models is given in Table 2.…”

“…The use of steel fibers instead of conventional steel stirrups could compensate for the initial cost of steel fibers, eliminate congestion of steel, and reduce the risk of defects and cracks [19][20][21][22]. Previous experimental studies verified the potential of steel fibers to improve the shear behavior of RC deep beams with and without openings [23][24][25][26][27][28]. Results of these studies are, however, limited to specific properties of the materials used, dimensions and geometry of the tested beams, and reinforcement details.…”

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

“…The noticeable advantage of steel fibre in transferring shear forces in the industry could be the use of fewer vertical stirrup reinforcements, as these types of reinforcements cannot limit the failure modes of deep beams [ 12 ]. The stirrup shear transfer mechanism in the deep beam is based on the confinement of the strut rather than its vertical shear effect that only depends on the shear span-to-span ratio [ 13 , 14 ].…”