Full-scale Glass Fiber-reinforced Polymer Research Articles

Compressive performance of full-scale GFRP composite sandwich wall panels with wood core

This paper investigated the compressive behaviors of sandwich wall panels consisting of glass fiber-reinforced polymer (GFRP) face sheets and Paulownia wood core experimentally and numerically. Vacuum-assisted resin infusion molding (VARIM) process was used to produce GFRP sandwich wall panel specimens. Four full-scale wall panels with different heights were tested under axial loading to study their failure modes and load-bearing capacities. The results revealed that buckling was the main failure mode of GFRP wall panels under the axial compression and the ultimate load-bearing capacities of specimens were improved the decrease of the height-to-thickness ratio. Experiments showed that decreasing the height-to-thickness ratio from 51.5 to 38.6 can effectively improve the ultimate load-bearing capacities of the wall panels by 124%. The experimental results were compared with finite element analysis (FEA) and analytical results were in good agreement. In addition, an equation was used to predict the load-bearing capacities of the wall panels suitable for the specimens with smaller height-to-thickness ratio.

Effect of confining stirrups and bar gap in improving bond behavior of glass fiber reinforced polymer (GFRP) bar lap splices in RC beams

Fiber-reinforced polymer (FRP) bars are becoming a popular replacement for steel rebars that are vulnerable to corrosion, especially under harsh corrosive environments. Despite several advantages for using FRP rebars, the bond between FRP bars and surrounding concrete has been a major concern that affects the behavior of FRP-reinforced structural members. The experimental program of this study comprises testing eight full-scale glass FRP (GFRP) reinforced beams under two-point loads. There were two control beams and six beams having rebar lap splices. The beams were reinforced using 2ϕ12 GFRP bars. The first control had continuous GFRP bars, and the 2nd control had GFRP lap splice conforming to the relevant ACI code. The lap splice was 65 times the bar diameter in six beams having lap splice. The contact lap and non-contact laps were used along with the variable spacing of shear stirrups in the lap zone (50, 100 mm, ∞, i.e., no shear stirrups). The lap splice, designed conforming to the ACI code, was found to be very conservative. The reduction in shear stirrups’ spacing in the lap zone and the gap between lapped bars was found to enhance the bond performance of GFRP bars by up to 31 %. The authors’ previous models for predicting development length and bond are found to show good predictions for the experimental results of the present study as well. Analytical models are developed for predicting with sufficient precision the peak load for GFRP reinforced beams with the two types of lap splices (non-contact and contact).

Experimental and Numerical Investigation of Joints for a Pultruded Fiber-Reinforced Polymer Truss.

Bolted connections usually govern the structural rigidity and load-carrying capacity of pultruded glass fiber-reinforced polymer (GFRP) truss structures. In this study, a novel bolted integrated gusset plate (IGP) connection is proposed to enhance the stiffness and capacity of GFRP truss structures. Nine double-lap shear tests of GFRP joints and numerical simulation were conducted to investigate the influence of variable design parameters of the bolted GFRP joints (number of bolts, width and thickness of GFRP, edge distance of bolts, and the employment of adhesive). Three full-scale GFRP truss joints were tested under static loading to study the response of a typical bolted connection, a bolted gusset plate connection, and the proposed IGP connection. The nine double-lap shear tests showed that the bolted-bonded mixed connection has 50% higher shear stiffness and 27% higher ductility compared with bolted joints, and bearing failure dominated the capacity of most specimens, which agreed well with numerical simulation results. Tests on the three full-scale GFRP truss joints showed that the bolted gusset plate can substantially reduce the number of cracks and improve the initial stiffness, but the maximum bearing capacity of the joints did not increase because the shear fracture of pultruded GFRP webs governs the capacity. The proposed IGP substantially increased the stiffness and capacity compared with the bolted connection and typical bolted gusset plate connection. The full-scale GFRP joint test is suggested to be used together with direct shear tests to study the performance of joints of the GFRP truss.

Study on eccentric behavior and serviceability performance of slender rectangular concrete columns reinforced with GFRP bars

Eccentric loading tests were performed on six full-scale glass fiber-reinforced polymer (GFRP)-reinforced concrete (RC) slender rectangular columns. The strain of the GFRP bar and concrete, the lateral deflection, and the flexural cracks width were measured at different load levels. The results indicate that under service loads, the lateral deflection and the flexural crack width of some specimens do not satisfy the serviceability criterion. At the peak load, the curvature range of the GFRP-RC slender columns is very close to that of typical GFRP-RC beams under flexural failure. This indicates that similar to GFRP-RC beams, excessive deflection and flexural crack widths may occur in eccentrically loaded GFRP-RC slender columns under service loads. In addition, an analytical model based on the well-known numerical integration method is presented to predict the load versus deflection relationship of eccentrically loaded GFRP-RC slender columns. Then, using the predicted results for the load versus the lateral deflection relationship, an analytical model is presented to predict the crack width of columns considering the bond-slip and tension-stiffening effects. These two models are found to reproduce the experimental results with satisfactory accuracy, which verifies that the two models can be used to predict the eccentric behavior of GFRP-RC slender columns.

Developing an innovative curved-pultruded large-scale GFRP arch beam

An arch glass fiber reinforced polymer (GFRP) I-beam with a 600 mm height was developed based on the latest curved-pultrusion technique to overcome the most critical design issues of large-scale GFRP beams, including excessive deflections and premature buckling failures. To achieve this goal, a review was first conducted regarding the complex buckling behaviors of pultruded GFRP beams, building a theoretical basis for the development of the curved beam. Then, a series of three-point bending tests for beams were conducted at full scale, in which the typical failure modes, load-carrying capacities and deflection and strain data were obtained. Compression flange delamination was found to be the dominant failure mode. The load–strain curves for flange and web plates demonstrated that the proposed beams were exempt from local buckling issues. Additionally, an analytical study and finite element modeling were carried out. Excellent agreement between experimental, analytical and numerical studies was observed. The design approach for conventional straight profiles is readily applicable to curved beams as the difference is limited. In the end, a 20-m-long full-scale GFRP pedestrian bridge was designed, constructed and tested. The great potential of the proposed curved-pultruded GFRP arch beam was successfully demonstrated.

Effect of Fiber Reinforced Polymer Tubes Filled with Recycled Materials and Concrete on Structural Capacity of Pile Foundations

This paper deals with analyzing the structural responses of glass-fiber-reinforced polymer (GFRP) tubes filled with recycled and concrete material for developing composite piles, as an alternative to traditional steel reinforced piles in bridge foundations. The full-scale GFRP composite piles included three structural layers, using a fiber-oriented material that was inclined longitudinally. Almost 60% of the fibers were orientated at 35° from the longitudinal direction of the pile and the rest 40 percent were oriented at 86° from the horizontal axis. The segment between the inner and outer layers was inclined 3° from the hoop direction in the tube. The behavior of the filled GFRP tubes was semi-linear and resulted in increasing the total ductility and strength of the piles. Adjusting the material’s properties, such as the EAxial, EHoop, and Poisson ratios, optimized the results. The lateral strength of the GFRP composite pile and pre-stressed piles are investigated under both axial compression and bending moment loads. Based on the conducted parametric study, the required axial and bending capacities of piles in different ranges of eccentricities can be reached using the combination of tube wall thickness and GFRP fiber percentages.

Experimental and numerical analysis of GFRP frame structures. Part 2: Monotonic and cyclic sway behaviour of plane frames

Part 1 [1] of this two-part paper presented an experimental study of the cyclic behaviour of a novel beam-to-column sleeve connection system for pultruded glass fibre reinforced polymer (GFRP) tubular profiles, and the numerical simulation of such behaviour. This Part 2 presents an experimental and numerical study on the sway behaviour of full-scale GFRP plane frames comprising the same tubular profiles and the aforementioned connection system. The GFRP frames were tested under quasi-static monotonic and cyclic loading, with and without infill walls, materialized by composite sandwich panels. The results of the tests show that high-load carrying capacity infill walls have a remarkable effect on the frames’ structural behaviour, significantly increasing their stiffness and load carrying capacity, as well as their cyclic performance, namely regarding energy dissipation. On the other hand, such improvement involved extensive damage in the frame elements, particularly in the beams, which at some point compromised their structural integrity. The numerical study included the simulation of the cyclic tests of the unfilled walls, by means of relatively simple finite element (FE) models, comprising frame elements and spring joints simulating the behaviour of the connections, in which the Pivot hysteresis model calibrated in Part 1 [1] was used. The comparison between experimental and numerical results shows that these simple and design-oriented FE models can provide an effective (and conservative) tool for the simulation of pultruded GFRP frames under horizontal cyclic loads.

Post-fire residual properties of GFRP reinforced concrete slabs: A holistic investigation

This paper provides critical data regarding the post-fire residual strength of Glass Fibre Reinforced Polymer (GFRP) reinforced concrete slabs. The residual tensile and bond strength of three types of GFRP reinforcing bars and the post-fire residual strength of a GFRP reinforced concrete slab are examined. For residual tensile strength, GFRP bars with a nominal diameter of 16 mm are exposed to temperatures up to 450 °C and tested after 24 h at room temperature. After 24 h, the specimens are loaded to failure at room temperature. For residual bond strength, pullout specimens are heated under various sustained load values. Finally, a full-scale GFRP reinforced concrete slab is tested at room temperature to evaluate the post-fire residual capacity after exposure to three hours of a standard fire. The residual tensile test results show that the bars that were exposed to 400 °C recovered at least 45% of the original strength while the residual bond strength is approximately 40% for pullout specimens that had experienced 300 °C. The post-fire residual strength of the slab is 68% of its room temperature flexural design strength with the bond loss at the ends of the slab being the governing mode of failure.

Behavior of GFRP-RC Slab–Column Edge Connections with High-Strength Concrete and Shear Reinforcement

AbstractThis paper presents the experimental results of seven full-scale glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) slab–column edge connections. The dimensions of the slabs wer...

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 Full-Scale Glass Fiber-Reinforced Polymer Reinforced Concrete Columns under Axial Load

Most current design guidelines and codes do not allow glass fiber-reinforced polymer (GFRP) bars to be used as compression reinforcement. This study investigates the compressive behavior of longitudinal GFRP bars in reinforced concrete (RC) columns. An experimental campaign on full-scale GFRP RC columns under pure axial load was undertaken using specimens with a 24 x 24 in. (0.61 x 0.61 m) square cross section. The results showed that the GFRP RC specimens behaved similarly to the steel RC counterpart when the longitudinal reinforcement ration is equal to 1.0%. The use of longitudinal GFRP bars was not found to be detrimental to the performance of RC columns, but the contribution of GFRP bars to column capacity was significantly lower than that of the steel bars in the steel RC counterpart. The 3 inch spacing of the GFRP ties strongly influenced the failure mode by delaying the buckling of the longitudinal bars, initiation and propagation of unstable cracks and crushing of the concrete core. Considerations for including GFRP reinforced columns in current ACI practice are discussed.

Finite Element Modeling for Deflection and Bending Responses of GFRP Poles

The use of the tapered glass fiber-reinforced polymer (GFRP) poles are well recognized as an alternative for traditional materials such as wood, steel, and concrete, in overhead power lines and distribution aerial networks. The current research work aims to assess the general behaviors of lightweight GFRP poles structures. A nonlinear finite element (FE) analysis is carried out to address the nonlinear behavior of tapered GFRP poles under lateral loads. The numerical results of the program are verified with the experimental results conducted on full-scale GFRP poles. The GFRP poles are fabricated using the filament winding technique; E-glass fiber and Epoxy resin are utilized for manufacturing these poles. There is very satisfactory agreement between the numerical results and the experimental results in terms of load-deflection relationship and ultimate load carrying capacity. The FE model was used to detect the performance of GFRP poles having service openings (holes). Several FE simulations with different combinations of parameters, such as fiber orientation, number of layers and thickness of layers, were employed. Evaluation of the deflection and bending strength characteristics of GFRP Poles (20, 33, 35 and 40 ft height) are presented. Optimum new designs for three zones along the height of the GFRP poles are proposed, under equivalent wind load. The ultimate load carrying capacity and flexural stiffness are improved with a significant saving in the weight by utilizing this design.

Fire testing of concrete beams with fibre reinforced plastic rebar

Abstract The behaviour of glass fibre reinforced polymer (GFRP) rebar reinforced concrete beams when exposed to fire is presented in this paper. The experimental programme involved fire tests based on British Standard 476 on two full-scale GFRP rebar reinforced concrete beams with dimensions in cross-section 350 mm×400 mm and 4400 mm total length with a span length of 4250 mm. The beams were designed and constructed according to Eurocode 2 and ACI-440. The purpose of this work was to evaluate the fire resistance of the GFRP reinforced concrete (RC) beams. GFRP rebars with thermoset resin were used for reinforcing beam 1 and GFRP rebars manufactured with thermoplastic resin were used for reinforcing beam 2. Shear reinforcement for beam 1 was GFRP stirrups and for beam 2 steel stirrups were used. Degradation in the flexural capacity due to fire was evaluated and compared. In this study, loaded heating tests were implemented with the aim of collecting basic data for the validation of a model presented in preceding papers by the authors.