This paper presents an experimental study on the efficacy of a lately introduced "near surface embedded" technique (NSE) for fabric reinforced cementitious matrix (FRCM) for the strengthening of reinforced concrete (RC) beams in shear; considering two test variables: (a) fabric type (glass and carbon) and (b) strengthening configuration (intermittent versus full). For this purpose, five (5) simply supported medium-scale RC rectangular beams have been tested under displacement controlled monotonic three-point loading. The experimental results showed that the FRCM system is effective in strengthening of shear deficient RC beams. An average of 62% gain in the shear capacity has been achieved due to the FRCM strengthening system. Carbon FRCM owning the higher axial rigidity showed better performance than that of glass FRCM. The average gain in the shear capacity for carbon FRCM strengthened beams was 22.5% higher than that for glass FRCM strengthened beams. Moreover, full strengthening configuration showed better performance than that for the intermittent configuration counterparts confirming the significance of the FRCM continuity and its quantity in enhancing the shear capacity of the strengthened beams.
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Textile reinforced mortar (TRM) is a composite material consisting of dry fibers embedded in a cementitious matrix, commonly used for strengthening masonry and concrete structures. In general, tensile characterization is required to identify the TRM mechanical properties, which are considered the key parameters needed for the structural design of strengthening systems. This paper presents the results of an experimental study conducted to investigate the tensile properties of TRM. In this effort, a total of 15 TRM coupons of 410 mm in length, 50 mm in width, and 10 mm in thickness were tested under uniaxial tensile load with clevis-type anchors. Three different types of textile materials were considered: carbon, glass, and polyparaphenylene benzobisoxazole (PBO). As for the study results, a common shape of the TRM tensile constitutive law was observed. Moreover, the average mechanical properties were listed for each type of TRM. Finally, the results and considerations presented in this work can enrich the literature with background data, which are beneficial for future applications of TRM systems in structural rehabilitation and repair.
In the case of heavily reinforced concrete structural members, bundled bars are required rather than spaced bars. The use of spliced bundled bars is necessary when available bar lengths are limited. No design recommendations regarding the use of bundled or spliced bundled FRP bars are available. The results of four-point flexural testing of nine concrete beams reinforced with spliced bundled CFRP bars are presented herein. The effects of the type of bundle and splice length on the bond strength of bundled CFRP bars are investigated. Based on the experimental results, a procedure for determining the critical splice length of FRP bars is presented and the corresponding values of bond stresses can be predicted. Moreover, the ultimate strength analysis method is used to predict the maximum stress in spliced bundled CFRP bars. Finally, comparisons with the existing recommendations regarding the use of bundled steel bars and the recommended modifications for bundled CFRP bars are presented.
The feasibility of strengthening concrete slabs in flexure, with and without cutouts, using the mechanically fastened (MF) FRP technique is investigated. Two series of large-scale reinforced concrete slabs are tested. The first series is comprised of five slabs without a cutout, and measuring 2,600×2,600×120mm; the second series consists of four slabs of the same dimensions with a central cutout measuring 800×800mm. The mechanically fastened system is found to be a valid alternative to the externally bonded system resulting in a rapid, economic, and effective strengthening technique for two-way concrete slabs. The increases in ultimate capacities of the MF FRP-strengthened slabs range between 30 and 70% over those of the unstrengthened specimens. In addition, finite-element modeling of MF FRP-strengthened slabs is introduced in this study. The interfacial behavior between the MF FRPs and the concrete substrate is accounted for by using appropriate interfacial models. Very good agreement is obtained between the test results and the numerical predictions.
The construction sector is well known for its critical environmental impact resulting from the consumed amounts of raw materials and the tremendous emissions of greenhouse gases. Therefore, scientists need to promote and study the environmental implications of using alternative solutions such as fiber-reinforced polymers (FRP) throughout their service life. FRPs have gained increasing popularity in the last few years due to their durability, high corrosion resistance, light weight and high strength. Life cycle assessment is considered one of the most important methods to investigate the environmental impacts of the FRP. The aim of this paper is to present an overview of fiber-reinforced polymer composites in concrete structures with an investigation focusing on their environmental and mechanical properties in civil engineering structures. The main focus is set on the properties of fiber-reinforced polymers, their use as a strengthening technique in concrete structural members and their environmental impact using the life cycle assessment method. The reported results from the literature reveal that utilizing FRP composites in structural members instead of traditional materials improves their strength and stiffness and reduces environmental impacts.
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ABSTRACT This study investigates the effectiveness of steel‐reinforced grout (SRG) for strengthening continuous reinforced concrete (RC) beams. A more sustainable alternative to conventional cementitious mortars, geopolymer mortar was employed in SRG‐strengthened RC beams while maintaining structural efficiency. An extensive experimental program involving 15 two‐span continuous RC beam specimens was conducted. The experimental parameters considered include the overall SRG stiffness (by varying the number of fabric layers and fabric density), the span coverage ratio, and the locations of strengthening. Additionally, the performance of steel fabrics in SRG was compared with other types of fabrics, including carbon, glass, and polyparaphenylene benzobisoxazole (PBO) fabrics. The results revealed that strengthening significantly enhanced the flexural capacity of the beams, with improvements ranging from 24% to 81%. Steel fabrics in SRG outperformed all other fabric types in terms of load‐carrying capacity. Low‐density SRG demonstrated superior bonding with the concrete substrate, leading to enhanced strengthening effects compared to high‐density SRG. Several failure modes were observed, including steel yielding, concrete cover separation, fabric rupture and slippage, and SRG debonding. A theoretical model based on SRG effective strain was utilized to predict the maximum load capacity of the strengthened beams.
