Glass Fiber-reinforced Polymer Shear Research Articles

Shear behavior of two-span continuous concrete deep beams reinforced with GFRP bars

To investigate the shear behavior of reinforced concrete (RC) continuous deep beams with glass fiber reinforced polymer (GFRP) bars, four large-scale beams with a constant shear span-to-overall depth ratio of 1.2 and different GFRP shear reinforcement ratios were tested. Digital image correlation technology was used to track the kinematics of diagonal shear cracks in the shear span. It was found that the moment redistribution in the deep beams was very limited. A tie-arch action was confirmed in the tested deep beams with the crack propagation and the strains developed in longitudinal reinforcements. For the beams without GFRP stirrups, the aggregate interlock contribution constituted 46.3% of the total shear resistance. For the beams with GFRP stirrups, however, the shear contribution of aggregate interlock was less significant. As the GFRP shear reinforcement ratio increased from 0% to 0.47%, the failure mode changed from shear compression failure to compression strut failure. As the shear GFRP reinforcement ratio increased from 0.24% to 0.32% and 0.47%, the load-carrying capacity increased by 35.5% and 73.5%, respectively. The minimum required GFRP shear reinforcement in ACI 440.1R-15 was ineffective for the tested GFRP-RC continuous deep beams in terms of shear capacity enhancement and shear crack control. Finally, a database of shear tests on continuous GFRP-RC beams was collected to assess the ability of strut-and-tie methods in three code guidelines.

Transverse Shear Capacity Predictions of GFRP Bars Subjected to Accelerated Aging Using Artificial Neural Networks

This paper presents the results of three different types of glass fiber-reinforced polymer (GFRP) bars subjected to different harsh environmental conditions. Three types of pultruded GFRP bars, namely, Bar A (13.04 mm dia.), Bar B1 (13.02 mm dia.), Bar B2 (10.19 mm dia.), and Bar C (13.22 mm dia.) were subjected to accelerated aging. GFRP specimens were exposed to four conditionings (alkaline, alkaline with salt, acidic, and water), two temperature regimes (20°C and 60°C), and three time regimes (3, 6, and 12 months). The mechanical strength retention of the bars investigated based on the transverse shear strength (TSS) test, conforming to ASTM D7617M-11 revealed a decline in the shear strength characteristics of specimens proportionally with the exposure time. In general, Bar A, Bar B1, and Bar B2 performed well, but Bar C performed the worst since Bar C exhibited the least mechanical strength retention at elevated temperatures. Scanning electron microscopy (SEM) of the cross section of the conditioned specimens revealed the nature of the evolution of deterioration and the state of glass fibers, polymeric resin matrix, and fiber-matrix interface, validating the decrease in transverse shear capacity of the bars. SEM micrographs showed fiber damage, with debonding occurring at the fiber-matrix interface and cracking of the polymeric resin. Leaching out of glass fibers into the matrix of varying degrees upon conditioning was observed through the X-ray mapping of silicon. Furthermore, strength prediction models developed using multiple linear regression and artificial neural network (ANN) techniques were compared. Coefficients of correlation (R2) of 0.94 and 0.76 and root mean square errors (RMSE) of 7.43 and 12.00 were obtained with models developed using ANN and multiple linear regression, respectively, showing that ANN can be used as a robust tool for GFRP shear strength prediction.

Experimental tests of FRP-HSC hybrid beams under four-point bending

This paper provides an experimental study of a new fiber-reinforced polymer (FRP)-high strength concrete (HSC) hybrid beam, which consists of a glass FRP (GFRP) I-shaped profile beam strengthened with a layer of HSC on top and carbon FRP (CFRP) sheets on the web. In this study, a total of two GFRP I-shaped profile beams, two GFRP I-shaped profile beams strengthened with CFRP sheets on the web and nine FRP-HSC hybrid beams were tested under four-point bending loading. The test parameters varied for the existence of CFRP sheets, the flange width of the GFRP profile, the width of the HSC slab, the type of shear connectors and the interfacial connection method. The test results indicated that bonding CFRP sheets, increasing the flange width and HSC slab width all showed positive effect on the ultimate bearing capacity and initial rigidity. Compared with U-shaped GFRP shear keys and inverted T-shaped GFRP shear keys, the hybrid beams using steel bolts had the highest ultimate load capacity and initial rigidity. The hybrid beams using the composite-bond interface (CB) performed better than the hybrid beams using wet-bond (WB) and dry-bond (DB) interfaces.

Flexural and shear behaviours of GFRP-reinforced concrete beams based on nonlinear finite element studies

This paper presents the finite element analysis of glass fiber-reinforced polymer (GFRP)-reinforced concrete beams. The research focuses on refining and validating concrete constitutive modelling within the commercial software ABAQUS. The accuracy of the proposed models is evaluated against a set of experimentally tested GFRP-reinforced concrete beams with, and without, GFRP shear reinforcement. The validated models are then used to conduct a parametric study on the influence of slenderness and shear reinforcement on the behaviour of GFRP-reinforced beams, the results of which are compared to the CSA S806-12 and ACI440.1R-15 design provisions. A discussion is provided on the effectiveness of the current design methods in predicting strength and failure modes of the GFRP-reinforced beams.

Developing of lightweight concrete sandwich wall panels with good thermal insulation properties for sustainable buildings

This research study aims at developing and investigating the mechanical and thermal properties of lightweight sandwich wall panels with good thermal insulation properties to reduce electric power for cooling of buildings. Within this study, several thermal insulation sandwich wall panels with two outer lightweight concrete layers and inner expanded polystyrene layer were developed and tested. Test parameters included the type of the outer concrete layers and the effect of using glass fiber reinforced polymer (GFRP) shear ties to connect the outer layers. Different ratios of polystyrene beads and vermiculite aggregates (53, 68 and 84% by volume of the natural coarse aggregates) were used to replace the natural coarse aggregates in the two outer concrete layers for better insulation properties and to develop lighter panels. Test results showed that using the GFRP shear ties was effective to connect the two outer layers of the panels. The results also revealed that increasing the amount of the polystyrene beads and the vermiculite aggregates decreased the thermal conductivity, the density, and the compressive strength of the panels. These values ranged from 0.41 to 0.25 W/m.K, 596 to 486 kg/m3, and 4.21 to 2.02 MPa respectively, for the panels with polystyrene beads. For the panels with vermiculite aggregates, these values were 0.46 to 0.34 W/m.K, 646 to 626 kg/m3, and 3.14 to 1.96 MPa, respectively. The results showed that the panels with polystyrene beads were stronger, lighter, and had better thermal properties. Using the developed panels will help to reduce the self-weigh of buildings resulting in smaller structural elements. In addition, the excellent thermal properties of the developed panels are expected to reduce power consumption and develop more sustainable buildings.

Punching Shear Strength of Reinforced Concrete Flat Plates with GFRP Vertical Grids

In this study, the structural behavior of reinforced concrete flat plates shear reinforced with vertical grids made of a glass fiber reinforced polymer (GFRP) was experimentally evaluated. To examine the shear strength, experiments were performed on nine concrete slabs with different amounts and spacings of shear reinforcement. The test results indicated that the shear strength increased as the amount of shear reinforcement increased and as the spacing of the shear reinforcement decreased. The GFRP shear reinforcement changed the cracks and failure mode of the specimens from a brittle punching to flexure one. In addition, the experimental results are compared with a shear strength equation provided by different concrete design codes. This comparison demonstrates that all of the equations underestimate the shear strength of reinforced concrete flat plates shear reinforced with GFRP vertical grids. The shear strength of the equation by BS 8110 is able to calculate the punching shear strength reasonably for a concrete flat plate shear reinforced with GFRP vertical grids.

Experimental study on the shear behavior of GFRP reinforced concrete beams strengthened using CFRP sheets

This paper presents the results of an experimental investigation on the shear capacity of reinforced concrete beams. The beams under consideration are reinforced with glass fiber-reinforced polymer (GFRP) bars. Also, the effect of shear strengthening on such beams is studied. For this purpose a total of four beams were tested where two served as control beams, while the other two were strengthened using U shape carbon fiber-reinforced polymer (CFRP) sheets, bonded externally. Each beam is 2.4 m long, simply supported and subjected to a four-point load under displacement control mode. The strengthened beams showed a noticeable increase in the load-bearing capacity of the specimen. The failure load recorded of these specimens was 208 kN, an increase of 25%. Moreover, the mode of failure changed from pure shear to concrete crushing in the compression zone. The results indicate that using CFRP sheets to strengthen GFRP reinforced beams in shear is a viable option. However, the results also suggest that the known adverse interaction between EB-CFRP and conventional steel stirrups could be applicable between EB-CFRP and GFRP shear reinforcement in strengthened beams. Therefore the predicted EB-CFRP shear capacity by ACI 440.2R turned to be unconservative when compared to the experimental results.

GFRP Shear Reinforcement for Slab-Column Edge Connections Subjected to Reversed Cyclic Lateral Load

In regions of high seismic activity, flat plate systems can be used as gravity force resisting systems, where special moment frames are provided as seismic force resisting systems. Nevertheless, all elements of the reinforced concrete (RC) structure must have sufficient deformability to be capable of deforming into the inelastic range. An efficient method of enhancing the deformability of flat plate systems is providing slab shear reinforcement. This paper presents the results of an experimental program evaluating the efficiency of two new types of glass fiber-reinforced polymer (GFRP) shear reinforcement in enhancing the deformability of GFRP-RC slab-column edge connections. Three full-scale connections were tested under gravity and uniaxial reversed-cyclic lateral loading, one connection was reinforced with GFRP shear studs, one with GFRP corrugated bars, and one had no shear reinforcement. The use of GFRP shear studs and corrugated bars increased the lateral load capacity of the connections by 47% and 44%, respectively. In addition, both types of GFRP shear reinforcement were able to enhance the deformability of the connections significantly, whereas the connection with shear studs was able to sustain deformations associated with 3.50% drift ratio without jeopardizing its gravity load capacity.

Lateral cyclic behavior of interior two-way concrete slab–column connections reinforced with GFRP bars

In flat plates, the use of high-strength concrete (HSC) in the slabs, and the presence of shear reinforcement in the vicinity of columns are considered effective, economical, and practical solutions for enhancing the punching shear performance of slabs. This paper presents the first-ever experimental results for interior concrete slab–column connections reinforced with glass-fiber-reinforced-polymer (GFRP) bars subjected to a combination of gravity and lateral reversed cyclic loads. Four full-scale slabs measured 2500 × 2500 mm with a thickness of 200 mm, and 300 mm square column extending 700 mm above and below the slab surfaces specimens were constructed and tested until failure. The main test variables were (i) flexural-reinforcement type (GFRP and steel bars); (ii) slab’s concrete compressive strength (NSC and HSC); and (iii) the use of GFRP shear reinforcement. All the tested specimens demonstrated adequate strength, deformation capacity, drift ductility indices, dissipated energy, and connection stiffness. The GFRP-reinforced NSC specimen without shear reinforcement showed adequate ability to withstand interstory drift up to 2.25% without punching failure. The GFRP-reinforced HSC specimen without shear reinforcement had a 33% higher lateral deformation and moment-transfer capacities compared to the GFRP-reinforced NSC specimen. The provision of GFRP-stirrups in the slab–column connection significantly influenced slab overall performance. The shear-reinforced specimen was able to sustain lateral drifts as high as 5% with no more than a 20% decrease in the moment carrying capacity. Moreover, the shear-reinforced slab was able to sustain the gravity load until the end of testing and only exhibited softer punching-shear failure with a gradual decrease in lateral loads.

Direct shear tests of glass fiber reinforced polymer connectors for use in precast concrete sandwich panels

The precast concrete sandwich panel (PCSP) is a popular structural type used for prefabricated construction. In this study, three kinds of glass fiber reinforced polymer (GFRP) connector, including a flat plate, a corrugated plate, and a hexagonal tube connector, were investigated for potential use in PCSPs. In-plane direct shear tests were conducted to evaluate the performance of the connectors based on a typical push-out configuration (i.e., three concrete wythes linked with connectors and two rigid foam layers in between). Twenty-five specimens were tested, and the parameters investigated consisted of GFRP laminate thickness, projected length, and shear force direction. The shear force vs. relative slip relationships and failure modes of all types of connector were compared and are discussed in detail in this paper. Meanwhile, finite element (FE) analysis was conducted to reproduce the test results. All three types of GFRP connector exhibited a progressive failure manner in spite of the linear brittle nature of the FRP materials; the corrugated plate connector achieved higher deformability than the flat plate connector, particularly when the GFRP laminate thickness was small; and the hexagonal tube connector exhibited similar behavior along two orthogonal directions, making them well suited for use as two-way connectors. The developed FE model was able to well predict the peak shear load and stiffness of all types of connector based on comparisons with the test results.

Evaluation of Shear Strength of Concrete Flat Plates Reinforced with GFRP Plates

The shear performance of concrete flat plates with glass fiber-reinforced polymer (GFRP) plate shear reinforcement was investigated through punching shear tests. Each GFRP plate was embedded in the concrete and included openings to permit the flow of concrete during fabrication. Punching shear tests were conducted on a total of 8 specimens, and the resulting crack and fracture formations, strains, and load-displacement curves were analyzed and compared. The experimental variables considered were the types of shear reinforcement, including steel stirrups or GFRP plates, and the shear reinforcement spacing. The experimental results show that the GFRP shear reinforcement effectively increased the shear strengths of flat plates. Furthermore, the applicability of two formulas was investigated: a modified version of a shear strength formula from ACI 318-14 and the ACI 318-14 fracture prediction formula.

Effect of cyclic loading on composite behavior of insulated concrete sandwich wall panels with GFRP shear connectors

Abstract A full-scale experiment was conducted to investigate the composite behavior of insulated concrete sandwich wall panels (ICSWPs) under monotonic loads and wind-induced cyclic loads. The experimental program consists of two groups, according to the applied loading type and the type of insulation, with the same configurations of glass-fiber-reinforced polymer (GFRP) grids. The degree of composite action in terms of the initial stiffness and ultimate strength were compared at the global level, and the degree of composite action in terms of the shear flow were compared at the local level (in accordance with the variables). The test results showed that the adhesive bonds based on the insulation absorptiveness and the mechanical bonds based on the insulation surface roughness and groove treatment were effective for inducing the desired composite behavior of ICSWPs in both monotonic loading and cyclic loading tests. The cyclic test group showed a lower degree of composite action compared to the monotonic test group at a constant rate. This is the case because cumulative fatigue loading damaged the GFRP strands and debonded the interface between the concrete and insulation. These results indicated that the adhesive and mechanical bonds between the insulation and concrete wythes can be used to estimate the design strength of ICSWPs with GFRP shear grids. Additionally, the reduction factor for the design strength by the fatigue effect should be considered in estimation of design strength.

Effect of Shear Studs and High Moments on Punching Behavior of GFRP-RC Slab–Column Edge Connections

AbstractThis paper presents test results of six full-scale glass fiber-reinforced polymer (GFRP) reinforced concrete slab–column edge connections. The test connections included two series with three connections each. The connections of Series 1 investigated the effect of a new type of GFRP shear reinforcement on the punching shear behavior of slab-column edge connections, while those of Series 2 investigated the effect of moment-to-shear ratio. For Series 1, one connection did not have shear reinforcement, while the other two connections had ribbed-deformed GFRP shear studs with headed ends at different radial spacing (120 and 80 mm). For Series 2, three different moment-to-shear ratios were applied to the connections (0.2, 0.4, and 0.6 m). The typical dimensions of the slabs were 2,800×1,550×200 mm with a 300-mm square column extending above and below the slab. The headed ends of the studs provided adequate anchorage, which allowed the studs to control the propagation of shear cracks and to increase the...

Behavior of GFRP-RC Interior Slab-Column Connections with Shear Studs and High-Moment Transfer

Six full-scale reinforced-concrete (RC) interior slab-column connections of glass fiber–reinforced polymer (GFRP) were constructed and tested to failure. The specimen consisted of a square slab with a 2,800-mm side length and a 200-mm thickness in addition to a 300-mm-square column stub extended for 1,000 mm above and below the slab. The test specimens were subjected to vertical shear forces and unbalanced moments. The test variables included the moment-to-shear ratio, GFRP double-headed shear studs ratio, and the type of GFRP bar surface texture (ribbed or sand-coated). The test results revealed that increasing the moment-to-shear ratio reduced the vertical shear capacity and increased the deflections and the strains at failure. Moreover, the presence of the GFRP shear studs enhanced the slab capacity but was not able to change the punching shear mode of failure. Furthermore, the used two types of GFRP bars showed comparable behavior. The results were compared with the predictions of the available fiber-reinforced polymer (FRP) design provisions such as those from Canada, the United States, and Japan. Finally, a new method is proposed to predict the punching shear capacity for the slabs with FRP shear studs.

Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction.

A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs) subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP) shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors.

Effects of insulation types on in-plane shear behavior of insulated concrete sandwich wall panels with GFRP shear connector

This paper describes the in-plane shear behavior of insulated concrete sandwich wall panels (CSWP) reinforced with corrugated glass fiber-reinforced polymer (GFRP) shear connector. The study included testing 8 insulated CSWP specimens with different types of insulation and corrugated shear connector. All specimens were loaded in direct shear. The test variables were embedment depth of shear connector and removal of adhesive stress between insulation and concrete. Test results indicated that the reinforcement of corrugated GFRP shear connector significantly increased in-plane shear strength. And dispersion reinforcement will be more effective in the case of expanded polystyrene (EPS) insulation. Meanwhile, reinforcement at a degree close to 45° will be more effective in the case of extruded polystyrene with surface treatment (XPSS) insulation. Increase of embedment depth of shear connectors was able to restrain pull-out phenomenon of shear connectors. And removal of adhesive force of insulation tended to decrease in-plane shear strength.

Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement

This paper presents the shear capacities of concrete beams reinforced with glass fiber reinforced polymer (GFRP) plates as shear reinforcement. To examine the shear performance, we manufactured and tested a total of eight specimens. Test variables included the GFRP strip-width-to-spacing ratio and type of opening array. The specimen with a GFRP plate with a3×2opening array showed the highest shear strength. From the test results, the shear strength increased as the strip-width-to-strip-spacing ratio increased. Also, we used the experimental results to evaluate whether the shear strength equations of ACI 318-14 and ACI 440.1R can be applied to the design of GFRP shear reinforcement. In the results, the ACI 440 equation underestimated the experimental results more than that of ACI 318.

파형 GFRP 전단연결재의 폭 및 너비에 따른 중단열 벽체의 면내전단거동

This paper describes the experimental results of insulated concrete sandwich wall panels (CSWP) with corrugated glass fiber-reinforced polymer (GFRP) shear connectors under in-plane shear loading. Corrugated GFRP shear connectors were used to improve the thermal property of insulated CSWP and to achieve composite action between the interior and exterior concrete wall panels. Test specimens were consist of three concrete panels with two insulation layers between concrete panels and middle concrete panels was loaded in the direction of gravity. To evaluate the effects of insulation types (extruded polystyrene, XPSS and expanded polystyrene, EPS), shear connector pitch (300 and 400 mm) and width (10 and 15 mm) on in-plane shear behavior of insulted CSWP, failure mode and shear flow-average relative slip relationship of specimens were investigated. Test results indicate that the bond stress between concrete panel and insulation is considerable initially. Especially in case of insulated CSWP without shear connector, initial stiffness of CSWP with XPSS is superior to that of CSWP with EPS. The shear connector's contribution to in-plane shear performance of insulated CSWP depends on the type of insulation.

Comparison of Shear Strength Equation for Flat Plates with GFRP Plate

In this study, shear test performed to investigate the shear behavior of flat plate that reinforced by embedded GFRP(glass fiber reinforced polymer) plate with openings. Shape of the GFRP shear reinforcement is a plate with several openings to ensure perfect integration with concrete. The test parameters include the distance between the column face and the first line of GFRP plate and number of GFRP plate vertical strip. The result of test showed that when number of GFRP plate vertical strip was increased, shear strength improved. The shear strength for flat plate reinforced GFRP plate in various codes including ACI 318, BS 8110, EUROCODE 2, and KCI were compared to provide more rational approach for reinforced concrete flat plates with GFRP plate.

Evaluation of Shear Strength for Reinforced Flat Plates Embedded with GFRP Plates

Abstract In this study, The purpose of this study is to experimentally investigate the shear behavior of reinforced flat plate embedded with GFRP(glass fiber reinforced polymer) plate with openings. The GFRP shear reinforcement is manufactured into a plate shape with several openings to ensure perfect integration with concrete. The test was performed on 7 specimens. the parameters include the type of reinforcement and amount of the shear reinforcement., From the test, we analysed the crack, failure mode, Strain, load-displacement graph. a calculation of the shear strength of reinforced flat plate with GFRP plate based on the ACI 318-11 was compared with the test results. The results of the experiment indicate that GFRP plate is successfully applied as a shear reinforcement in the flat plate under punching shear. Keywords :shear reinforcement, flat plate, glass fiber reinforced polymer(GFRP), shear strength. † Corresponding author: Tel: +82-31-201-2542; E-mail: kimhc@khu.ac.krReceived March 13 2014; Revised March 27 2014;Accepted March 28 2014Ⓒ2014 by Computational Structural Engineering Institute of KoreaThis is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.