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Funding Information: The funding for this research was provided by the National Priorities Research Program of the Qatar National Research Fund (A member of the Qatar Foundation) under the award no. NPRP 8-418-2-175. The statements made herein are solely the responsibility of the authors and do not necessarily reflect the opinions of the research sponsor. The authors would like to also thank Dr. Paolo Casadei from Kerakoll Spa for providing and installing the galvanized steel mesh sheets. Publisher Copyright: © 2022 The Authors Steel reinforced polymers (SRP) are useful in a wide range of applications, including strengthening of existing reinforced concrete (RC) structures, due to their numerous advantages like high strength, low maintenance, light weight and low cost. As such, galvanized steel mesh (GSM) has emerged as an option in the strengthening of RC structures. Although numerous studies were performed on GSM strengthened RC beams, the durability of such strengthening systems is yet to be fully understood. This paper presents an experimental and numerical study to investigate the strengthening effect of GSM on RC beams as well as the time-depended behavior of RC beams with and without strengthening. Reinforced concrete beams without strengthening were used as control beams. For the strengthened beams, both high cord density galvanized steel mesh (HSM) and medium cord density galvanized steel mesh (MSM) were used after which the beams were exposed to Qatar atmospheric environment for different periods of time following 28 days of water curing. Finite element analyses using ABAQUS software were conducted to predict the mechanical behavior of the RC beams with and without strengthening. The results showed an improvement ranging from 46% ∼ 57% in the ultimate load of GSM strengthened beams, with a higher initial cracking load ranging from 3% ∼ 35% when compared to the unstrengthened beams. On the other hand, the time-dependent effect of the concrete has limited influence on the initial cracking load of both systems (before and after strengthening) while the ultimate load increased gradually with time due to the strength development of concrete. The results obtained from this study are useful in improving the design, construction, and maintenance of RC beams strengthened with GSM laminates.

This paper explores the viability of using aluminum alloy (AA) plates as an externally bonded reinforcement (EBR) material that could overcome some of the shortcomings of the prevailing steel and FRP materials and provides new advantages. A total of 32 prisms with different concrete strengths have been prepared as single shear test specimens with AA plates bonded to the prisms at different lengths using epoxy adhesive. Single shear tests were conducted on the prism specimens until failure. Load-extension and load-strain values were recorded. Bond stress and bond slip values were calculated. Test results have shown that plain untreated AA surface is susceptible to premature debonding; however treating the AA surface, by roughening it, increases its bond strength and ultimate load capacity considerably. Generally, the ultimate load and maximum bond stress increased with the increase of the bonded length and concrete strength, on the average, for the AA roughened surface compared to the AA plain untreated surface, by up to 457%, 327%, respectively. It is also observed that the modes of failure were influenced by the changes in the bonded length, concrete strength and AA surface treatment.

Strengthening of reinforced concrete (RC) structures via external bonded fiber-reinforced polymer (EB-FRP) systems has been widely documented and used. This form of retrofitting has proven to be effective in enhancing flexural and shear capacity of RC beams. However, it is limited due to premature debonding of the FRP laminates prior to utilizing the laminates strength, and typically results in brittle member failure. To overcome this issue, studies have shown that proper anchorage systems mitigate debonding and enables the achievement of higher strengthening levels. Out of the many anchorage systems researched, FRP splay anchors have proven to be effective in enhancing member’s capacity by delaying the laminates debonding. However, the literature is lacking adequate information on the effect of splay anchors on the performance externally strengthened RC beams in shear. Accordingly, five shear deficient RC T-beams specimens were cast and strengthened with CFRP U-wrapped laminates and anchored with CFRP anchors. The parameter investigated in this study is the anchor dowel diameter. Three dowel diameters were tested: 12 mm, 14 mm, and 16 mm. The performance of the anchored U-wrapped specimens in terms of failure modes, load-deflection responses, shear strength, strain in CFRP laminates, and ductility is compared to that of unstrengthened and unanchored strengthened control specimens. Test results showed that CFRP anchors delayed debonding of the U-wraps, improved the shear strength of unanchored U-wraps, and significantly enhanced the ductility of the beam specimens. In addition, it was concluded that anchoring CFRP laminates with CFRP anchors highly utilized the strain attained in CFRP laminates. No clear trend was observed between anchor diameter and ultimate load-carrying capacity of the specimens. Based on the results of this study, anchor dowel diameter of 14 mm was found optimum for an anchor embedment depth of 85 mm.

Strengthening of deficient reinforced concrete (RC) structures had been one of the major concerns of researchers over the past few decades. Thus, new materials are being discovered to ease the process of externally strengthening RC structures. One of the various strengthening materials is Galvanized Steel Mesh (GSM) that is available in different cord densities. High and low cord-density GSM sheets can be externally bonded to RC structures using epoxy adhesives, while only low cord-density GSM sheets can be externally bonded with cement Mortar. In this experimental study, low cord-density GSM sheets (3.15 cords/cm) were bonded with cement mortar to the soffit of RC beams surfaces. A total of four RC beams were cast, three of which were externally strengthened in flexure with GSM sheets and bonded with mortar and the remaining beam was kept as a control un-strengthened specimen. In order to avoid the brittle delamination failure mode, one of the strengthened specimens was anchored with end U-Wrap carbon-fiber reinforced polymer (CFRP) sheets, while the other strengthened specimen was anchored with intermediate U-Wrap CFRP sheets, and the remaining third strengthened specimen was not anchored, to serve as a control strengthened specimen. All specimens were subjected to four-point loading test and the load-deflection response curve of each specimen was recorded. It was observed that flexural strengthening using GSM sheets increased the ultimate-load capacity of strengthened specimens by a range of 41.8 to 51.4 %, when compared to control un-strengthened specimen. While, no strength increase was observed when comparing anchored strengthened specimens to non-anchored strengthened specimens. However, the ductility of end anchored specimens increased by 142.1 and 270% when compared to control and non-anchored specimens, respectively. In addition, the ductility of intermediate anchored specimens increased by 134.1 and 257.3 % when compared to control and non-anchored specimens, respectively. Thus, it can be concluded that GSM laminates if properly anchored can enhance the strength and ductility of RC beams in flexure.

Carbon fiber reinforced polymers (FRP) have been used widely as Externally Bonded Reinforcing (EBR) materials for strengthening and retrofitting of RC structural members, both in flexure and shear. The use of high strength Galvanized Steel Mesh (GSM) strengthening material has recently gained wide acceptance as well. Both CFRP and GSM have many advantages and some shortcomings. One of their major shortcoming is the lack of ductility. Recently developed Aluminum Alloys (AA) has high ductility and some desirable features that may overcome some of the shortcomings of GSM and CFRP laminates. The major aim of this research is to develop a hybrid ductile strengthening system by combining AA plates with GSM and CFRP laminates to strengthen RC beams in flexure. An experimental program that includes tensile test of six coupon specimens and five flexure tests of beam specimens were conducted. The test results showed the effect of hybrid combination on both strength and ductility of the tested beams and that the newly proposed hybrid systems are promising in improving the flexural behaviour in terms of strength and ductility. The tested hybrid coupons of AA with high density steel mesh (SMH) and AA with CFRP showed an increase in the strain capacity by 6.52 and 4.55 times, respectively compared to that of GSM and CFRP alone. The flexural capacity of the beams strengthened with hybrid laminate increased by around 28% over the control beam, while the beam strengthened with hybrid GSM and AA (SMH+AA) laminate showed an ultimate deflection equivalent to 98.5% of the un-strengthened control beam. The failure modes of the tested beams included debonding and delamination and they were influenced by the type of hybrid system used.

Shear failure in reinforced concrete (RC) beams is brittle and undesirable type of failure. This paper investigates the use of bore-epoxy as an anchorage technique for CFRP sheets used as externally bonded shear strengthening reinforcement. Five shear deficient RC beams were cast, one was used as a control (C), one was strengthened with two side CFRP sheets as EBR without anchorage and used as a second control or reference beam (S-EBR) and the remaining three were strengthened using two side CFRP sheets as EBR with bore-epoxy anchorage of different bore diameters (15 mm, 25 mm, 35 mm). The RC beam specimens were tested under four point bending. Load-deflection and load-strain values were recorded. The results showed that the bore-epoxy anchorage system delayed the CFRP sheets de-bonding and increased the shear capacity of the tested specimens by up to 10% compared to the S-EBR control beam and by up to 56% compared to the unstrengthen control beam. The load-deflection curves showed a considerable increase (up to 63.5%) in the deflection of the RC beams strengthened with bore-epoxy anchorage compared to the control beam resulting in a more ductile failure. The failure modes of the tested RC beams varied with the strengthening and the anchorage system used, but they were predominately delamination for the beams strengthened with externally bonded CFRP sheets on bore-epoxy anchorages.

Strengthening of existing reinforced concrete (RC) structures by externally bonding carbon fiber–reinforced polymers (CFRP) applied to the concrete substrate has proven to be effective in ...

This paper investigates experimentally the shear strength behavior of reinforced concrete (RC) beams cast with Lava lightweight aggregates as a replacement of normal coarse aggregates. A total of 24 shear deficient RC beams were fabricated and cast with normal (NWC) and lightweight (LWC) concrete and tested under three-point bending after 28 and 56 days. The variables of the experimental program include type of aggregate, concrete compressive strength, and beam size. The experimental results include load—deflection response curves along with failure mode for each beam specimen. The experimental result showed that all beams failed in a similar fashion, due to diagonal tension shear crack. However, a larger number of cracks with less spacing occurred in the LWC beams as compared to NWC specimens. Based on the experimental results, it can be also concluded that LWC specimens tested after 56 days achieved comparable shear strength results to that of NWC beams. In addition, the strength reduction factor (λ) for LWC specimens was in the range of 0.69–0.98. The concrete shear strength (V c) was also predicted using different shear design provisions and the results has shown that Eurocode 2 provisions yielded the lowest C.O.V. of 2.3 and 10.2% for NWC and LWC specimens, respectively.

The conventional method of strengthening reinforced concrete (RC) beams in flexure is via bonding carbon-fiber reinforcement polymer (CFRP) laminates to the beam’s soffit. However, the beam’s soffit could be narrow or inaccessible for strengthening. To overcome such obstacles, this paper explores the feasibility of strengthening RC beams in flexure by side-bonded CFRP composite sheets. Accordingly, a total of nine RC beams have been cast, eight of which were strengthened in flexure with different configurations of bottom-bonded and side-bonded CFRP sheets, and tested under four-point bending till failure. The load-deflection response curves, failure modes, and ductility of the tested specimens were recorded and compared. Overall, it is observed that specimens strengthened with similar amount of reinforcement are comparable with percent increase in the flexural strength over the control beam ranged from 62 to 92% for bottom-bonded and 39.7–93.4% for side-bonded strengthened beams. In addition, an analytical model based on ACI 440.2R-08 guidelines is developed and the predicted flexural strength was in good agreement with experimental results with differences ranging between 2.4% and 6.8%. It is concluded that the proposed side-bonded strengthening scheme is a valid alternative to the bottom-bonded scheme of strengthening of RC beams in flexure.