Glass Fibre Reinforced Polymer Dowels Research Articles

Load transfer of small-diameter GFRP and stainless steel doweled-joints in slabs-on-ground

Large diameter steel and glass fiber-reinforced polymer (GFRP) dowel bars are commonly used in rigid concrete pavements in highways for load transfer across joints to combat the concrete deterioration due to corrosion of steel dowels. Small-diameter GFRP dowel bars can be used at the expansion joints in slabs-on-ground, walkways, industrial floors and concrete-lined channels, which are not subjected to heavy traffic loads. This study investigated the performance and behavior of small-diameter GFRP dowels. GFRP dowels with three diameters (14 mm, 16 mm, and 38 mm) and stainless steel dowels (12 mm dia.) were embedded across a 25 mm-wide joint in a test slab with overall dimensions of 1500 × 750 × 200 mm3. The variables of the study were the type of dowel material (GFRP and stainless steel), the diameter of GFRP dowels, the spacing of the dowels (200 mm and 250 mm c/c), and the type of loading (monotonic and cyclic). The slabs were loaded up to the failure of the joints under a concentrated load applied at the edge of the joint. The performance of the dowel-jointed slab specimens was investigated based on the cracking and ultimate loads, modes of failure, and load-displacement response. The ability of the small-diameter dowel bars to transfer displacements across the joint was quantified using the quantitative measures of joint effectiveness (E), load transfer efficiency (LTE), and relative deflections (Δ). Failure of the specimens with 14 mm and 16 mm diameter dowels occurred predominantly due to shear failure of the dowels before the cracking of concrete. However, for the specimens with large-diameter GFRP dowels and the stainless steel dowels, failure was associated with cracking of the concrete. A smaller spacing of the GFRP dowels and a longer embedment length gave a stiffer load-displacement response. Reducing the spacing from 250 mm to 200 mm resulted in a 4.1-fold reduction in relative deflection under the AASHTO H10 design wheel load (∼35.6 kN). Increasing the dowel length had no significant effect on the load-carrying capacity of the dowel-jointed slabs. Cyclic load tests on the specimens revealed that the joint effectiveness (E) and the load transfer efficiency (LTE) of GFRP dowels were within the AASHTO and ACPA limits up to a concentrated load higher than the AASHTO HL93 dual tandem-axle wheel load (∼55.6 kN).

Numerical evaluation of the combined effect of dowel misalignment and wheel load on dowel bars performance in JPCP

The paper presents a comprehensive experimental and analytical (3D finite element modelling-FEM) investigation into the combined effect of dowel misalignment and wheel load on dowel bars response in Jointed Plain Concrete Pavement (JPCP). The study also investigated the suitability of Glass Fibre Reinforced Polymer (GFRP) dowels as an alternative material to epoxy-coated steel dowels. The experimental tests focused on the pull-out load joint-opening behaviour and relative deflection (RD) of the joint. A 3D FEM was developed to investigate the most frequent cases of dowel misalignment for steel and GFRP dowels and estimate the damaged volume in the surrounding concrete pavement due to dowel misalignment. The results showed that using GFRP dowels significantly reduces the pull-out load required to open the joint and also reduces joint lockup possibilities even when dowel misalignment exists. Consequently, the surrounding pavement deteriorates much less.

Design of prestressed precast pile splice using glass fiber reinforced polymer (GFRP) dowels

For various reasons including shipping and operation limitations and unforeseen soil conditions, it often happens that splicing of precast-prestressed concrete pile (PPCP) segments has to be performed at the site to achieve longer lengths. Epoxy dowel splice is one of the common systems used for splicing PPCPs. The objective of this study was to investigate the effectiveness of glass fiber reinforced polymer (GFRP) dowel bars proposed as an economic corrosion-resistant option for use in pile splices. Analysis was performed for a standard 18×18 in (457×457 mm) PPCP. Two series of material properties were considered for GFRP in the proposed design, mechanical properties in accordance with the Florida Department of Transportation (FDOT) Specifications and improved mechanical properties (2021) under consideration by ASTM D30 Committee. The results show that among various sizes and configurations, the use of 8 #10 GFRP dowels with arrangement similar to that of standard steel dowel splice provides for an optimum design. As an example, the developed design was compared to FDOT requirements. The proposed configuration of GFRP dowels satisfies the requirement for axial compression and tensile capacities. The nominal pure bending capacity of the proposed design is estimated to be 84% and 93% of the threshold capacity for the existing material and improved material, respectively. The flexural resistance of the splice increases with increasing axial compression on the pile to an extent. The use of improved GFRP material for dowel bars shows noticeable enhancement in the flexural resistance so as the use of larger diameter dowels. Detailed drawings for the proposed design were also developed and are presented in this paper.

Experimental investigation on the combined effect of dowel misalignment and cyclic wheel loading on dowel bar performance in JPCP

A number of previous studies indicated that the joint lockup due to misalignment and looseness of dowel bars may cause joint distress in Jointed Plain Concrete Pavement (JPCP). This article reports a detailed experimental investigation of pull-out load and joint lockup due to dowel misalignment; and dowel looseness caused by the combined effect of misalignment and cyclic traffic load. The test slabs were supported on steel beams with an appropriate amount of vertical stiffness so as to incorporate the effects of underlying layers of real pavements. The article also provides an experimental investigation to assess the suitability of Glass Fibre Reinforced Polymer (GFRP) bars as alternative dowel bars to reduce joint lockup and associated detrimental effects at the dowel-concrete interface compared with epoxy-coated steel dowels. The results show that the 38 mm GFRP dowels that have equivalent flexural rigidity (EI) to 25 mm steel dowels can withstand the cyclic traffic load, significantly reduce joint lockup and dowel looseness, and can provide adequate Load Transfer Efficiency (LTE). It was also observed that misalignment affects dowel looseness significantly more than the number of cycles for traffic load. The slab-base separation and orientation of misaligned dowels have significant effects on the load required to open the joint.

Laboratory evaluation of chemical resistance of pultruded GFRP dowels for concrete pavement

This paper presents mechanical, microstructural and physical characterization of glass fibre-reinforced polymer (GFRP) rods used as dowels for concrete pavement exposed to different types of conditionings. Two types of GFRP dowels fabricated with polyester and vinylester resins were studied. GFRP dowels were exposed to different alkaline and saline solutions at 23 °C during 90 days to simulate the effect of the concrete environment. GFRP dowels were also subjected to cyclic freezing and thawing. The measured short beam shear strengths and flexural modulus of elasticity of the GFRP dowels before and after exposure were considered as a measure of the durability performance of the specimens. In addition, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy were used to characterize the aging effect on the GFRP dowels. The results showed the very high long-term durability of vinylester GFRP dowels exposed to tap water, CaCl2, NaOH and CaOH2 solutions, and to freeze/thaw cycles. On the other hand, the test results have shown that polyester-based GFRP dowels present an uncertain stability in the different environments simulating the field service conditions, due to plasticizing and/or irreversible chemical degradation of the polymer matrix.

Evaluation of performance and design of GFRP dowels in jointed plain concrete pavement – part 2: numerical simulation and design considerations

The article presents a numerical investigation using three-dimensional finite element analysis (FEA) to compare the performance of glass fibre reinforced polymer (GFRP) and steel dowel bars as load transfer devices across the transverse joints of jointed plain concrete pavements (JPCP). The FEA model used concrete damaged plasticity formulation to characterise the concrete pavement; elastic, transversely isotropic material characteristics were assumed for the GFRP dowels and classical metal plasticity formulation was used for the steel dowels. The numerical results were validated with the experimental results, and a good agreement was achieved. The results showed less stress concentration in the concrete underneath the GFRP dowels (38 mm diameter) compared with the steel dowels (25 mm diameter) of similar flexural rigidity. Finally, on the basis of a detailed parametric study, design considerations for the GFRP dowels in JPCP are suggested.

Performance of Glass Fiber-Reinforced Polymer-Doweled Jointed Plain Concrete Pavement under Static and Cyclic Loadings

Glass fiber-reinforced polymer (GFRP) dowel bars are a non-corrodible and maintenance-free alternative that will potentially reduce the life-cycle cost of jointed plain-concrete pavement (JPCP), especially in harsh environmental conditions. This paper investigates the performance of GFRP dowels in JPCP under static and cyclic loads. In addition, it compares their behavior with that of commonly used epoxy-coated steel dowels. GFRP and epoxy-coated steel dowels were employed in fabricating a total of six JPCP prototypes (slab-joint). The test prototypes measured 2440 mm long x 610 mm wide x 254 mm deep (96 x 24 x 10 in.). The slabs were cast with a butted joint; each test prototype contained two dowel bars. The test parameters included: 1) dowel-bar type (GFRP and epoxy-coated steel); 2) dowel-bar diameter (34.9 and 38.1 mm [1.38 and 1.50 in.] for GFRP; 28.6 mm [1.13 in.] for epoxy-coated steel); and 3) loading scheme (static and cyclic). The test results revealed that both 34.9 and 38.1 mm (1.38 and 1.50 in.) GFRP dowels showed crack patterns and failure modes similar to those of the epoxy-coated steel dowels. The 34.9 and 38.1 mm (1.38 and 1.50 in.) GFRP dowels and 28.6 mm (1.13 in.) epoxy-coated steel dowels were not affected by 1,000,000 cycles between 10 and 50 kN (2.25 and 11.24 kip). In addition, both the 34.9 and 38.1 mm (1.38 and 1.50 in.) GFRP dowels showed higher joint effectiveness than that of the 28.6 mm (1.13 in.) epoxy-coated steel dowels. This paper also discusses the results of a field application in which the GFRP dowels were implemented in a new concrete-pavement highway in Mirabel, QC, Canada.

Evaluation of performance and design of GFRP dowels in jointed plain concrete pavement – part 1: experimental investigation

Dowel bars are provided at the transverse joints of the jointed plain concrete pavement to allow for expansion and contraction of the pavement due to moisture and temperature changes. This paper presents experimental and analytical investigations for the deflection response of glass fibre-reinforced polymer (GFRP) dowels for different joint widths and concrete grades. The results were compared with those obtained from investigations into the conventional epoxy-coated steel dowel bars of similar rigidity. The experimental results showed that the 38 mm (1.5 in.) GFRP dowels perform better in terms of joint face deflection compared with 25 mm (1 in.) epoxy-coated steel dowel bars. In addition, these results showed that the deflection of the GFRP dowel was significantly affected by changing the concrete compressive strength and the joint widths.

Experimental Evaluation of Connections in Hybrid Precast Concrete Bridge Truss Girders

An innovative, corrosion-free, precast, prestressed concrete truss girder has been developed for short- and medium-span, slab-on-girder bridges. The girder consists of top and bottom concrete flanges connected by precast vertical and diagonal members and made of fiber-reinforced polymer (FRP) tubes filled with concrete. The verticals and diagonals are connected, respectively, to the concrete flanges by means of glass FRP dowels and stud reinforcement made of corrosion-resistant steel or FRP material. The flanges are pretensioned with carbon FRP tendons. The deck slab is reinforced with corrosion-resistant steel bars in the bottom transverse layer and with glass FRP bars in the bottom longitudinal and the top layers. The girders may be posttensioned with external carbon FRP tendons to balance the slab weight and to provide continuity in multispan bridges. The new system has the advantages of light weight and enhanced durability. The light weight reduces the initial cost and allows for longer spans. The improved durability reduces the maintenance cost and extends the structure's life span. This paper describes the general details of the system and presents an experimental evaluation of its critical components, namely, the FRP tubes and the truss connections. Two types of FRP tubes and four types of connections were investigated. The results are presented of tests of eight connection specimens under static loading and four specimens under fatigue. The tests showed excellent performance of the connections when filament-wound tubes and continuous double-headed studs were used.

Experimental investigation into a ductile FRP stay-in-place formwork system for concrete slabs

This paper presents the findings of an experimental investigation into a novel FRP stay-in-place (SIP) structural formwork system for concrete slabs with particular emphasis on its ability to exhibit ductility. The system consists of a moulded Glass Fibre Reinforced Polymer (GFRP) grating bonded to square pultruded GFRP box sections as structural stay-in-place formwork for a concrete slab. Holes cut into the top flange of the box sections at a variable spacing allow concrete GFRP dowels to be inserted to act as shear studs. Experimental results indicate that the proposed shear connection provides robustness and ductility to the system, thus helping to solve the notorious ductility issue associated with construction using FRP materials.

Laboratory Characterization and Evaluation of Durability Performance of New Polyester and Vinylester E-glass GFRP Dowels for Jointed Concrete Pavement

AbstractThis paper presents an experimental study that investigated the physical, mechanical, and durability characteristics of newly developed vinylester- and polyester-based glass-fiber-reinforced polymer (GFRP) dowels through a collaboration research project with the Ministry of Transportation of Quebec (MTQ). Durability performance was first evaluated with a preliminary set of conditionings in different solutions. The long-term performance was then assessed under harsh alkaline exposure simulating the concrete environment. The alkaline exposure was achieved by immersing the dowels in an alkaline solution at elevated temperatures to accelerate the effects. Thereafter, the properties were assessed and compared with the unconditioned reference values. The test parameters were (1) type of resin (vinylester and polyester), (2) diameter of GFRP dowels (25.4–44.8 mm), (3) temperature (23, 50, and 60°C), and (4) conditioning time (30, 60, and 180 days). The test results revealed that the vinylester-based GFRP...

Performance Properties of GFRP Dowels in Concrete Pavement Joints

Dowels are used in jointed plain concrete pavements to provide lateral load transfer across transverse joint through shear force, effective load transfer at lateral joints can reduces stresses in the slabs. Steel dowels are generally used in engineering practice, but corrosive substance such as carbon chloride ions ,dioxide can free access and easily dispersed along the length of the steel dowels, therefor rapid corrosion can occur which can lead to premature failure of the transverse joint. Glass fibre reinforced polymer (GFRP) dowels have been recently introduced as a possible solution to the corrosion problem posed by steel dowels. This paper given a comparison of the maximum shear forces of none eroded GFRP dowel at the joint face with the help of a three-dimensional finite-element model and investigated the performance of GFRP dowels under static and cyclic load. According to the experiment results, the larger-diameter GFRP dowels were found to perform the best in this study.

Bond Properties of Glass Fibre-Reinforced Polymer Dowel Bars in Jointed Concrete

Dowel bars installed at the transverse joints of concrete slabs reduce the deflection and stress at the joint edges while transferring the traffic load from one slab to the next. We used draw-out and push-back tests to simulate the movement of a glass fibre-reinforced polymer (GFRP) dowel bar installed in a horizontal linear section of a concrete pavement undergoing repeated shrinkage and expansion movements. The tests were carried out on three different sizes and shapes of dowel bar. The pull-out strength was lower in GFRP dowel bars with an elliptical cross section, which would be a better fit as a load transfer device in concrete pavement. Since they do not restrict shrinkage and expansion of concrete pavement and allows free movement, they would prevent destruction of a concrete slab by curling.

The Durability of Glass Fibre-Reinforced Polymer Dowel after Accelerated Environmental Exposure

The corrosion of steel dowel causes potential problems in jointed concrete pavement that necessitate alternative dowel materials. Glass fibre-reinforced polymer (GFRP) dowel is a possible maintenance-free alternative that will potentially reduce the overall lifetime cost of pavement. This study evaluated the long-term durability of GFRP dowel. It was subjected to accelerated ageing at an elevated temperature under five environmental conditions: alkaline, water, salt, calcium chloride and repeated freeze-thaw cycles. The durability was quantified using the apparent horizontal shear strength test. The results of the accelerated ageing test were compared with those of the natural environment. Based on the test results, the durability of GFRP dowel is acceptable and it is very resistant to the detrimental affects of accelerated ageing.

Composite T-Beams Using Reduced-Scale Rectangular FRP Tubes and Concrete Slabs

A composite system consisting of rectangular glass fiber reinforced polymer (GFRP) tubes connected to concrete slabs, using GFRP dowels has been developed. Seven beam specimens have been tested, including hollow and concrete-filled GFRP tubes with and without concrete slabs. Beam–slab specimens had two different shear span-to-depth ratios and one specimen had carbon–fiber reinforced polymer (CFRP)-laminated tension flange for enhanced flexural performance. Additionally, three double-shear GFRP tube-slab assemblies have been tested to assess the shear behavior of GFRP dowels, in both hollow and concrete-filled tubes. Three compression stubs of concrete-filled tubes were also tested by loading them parallel to the cross-section plane, to study GFRP web buckling behavior. The study showed that GFRP dowels performed well in shear and that composite action is quite feasible. While hollow tubes can act compositely with concrete slabs, more slip between the tube and slab would occur, compared to a concrete-filled tube-slab system. Simplified models are proposed to predict critical web buckling load of fiber reinforced polymer (FRP) tubes. Based on the models, a critical shear span-to-depth ratio of 4 was determined, below which web buckling may occur before flexural failure.

Concrete-Filled, Glass Fiber–Reinforced Polymer Dowels for Load Transfer in Jointed Rigid Pavements

Smooth, round steel dowels have been used for nearly a century to transfer wheel loads across concrete pavement joints. Dowels are subjected to shear and bending stresses caused by traffic loads in addition to curling stresses caused by temperature gradients in pavement slabs. Over time, the use of deicing salts corrodes steel dowels and causes damage to concrete pavement joints. Alternative dowel materials, such as stainless steel and glass fiber–reinforced polymer (GFRP), have been introduced in recent years. The dominant size of dowels for highway pavements has remained the same, typically 38 mm in diameter, and costs can be considerably higher for stainless steel compared with epoxy-coated steel dowels of the same size. Experimental tests at the University of Manitoba, Canada, examined the performance of four dowel types, including the standard 38-mm epoxy-coated steel; 38-mm solid, pultruded GFRP dowels; and 50-mm and 63.5-mm concrete-filled GFRP tube dowels. The dowels were cast in small concrete slabs of typical pavement thickness and instrumented with strain and displacement gauges. Behavior of the dowels was evaluated on the basis of measured displacements, bending strains, and performance for more than 1 million load cycles. Concrete-filled GFRP tube dowels exhibited considerably smaller displacements and, therefore, lower bearing stresses than 38-mm steel and solid GFRP bars. After 1 million load cycles, concrete-filled dowels and concrete slab showed no signs of fatigue damage or loss of load transfer, indicating a reasonable potential for replacing steel dowels, particularly in corrosive environments.

Concrete-Filled, Glass Fiber-Reinforced Polymer Dowels for Load Transfer in Jointed Rigid Pavements

Smooth, round steel dowels have been used for nearly a century to transfer wheel loads across concrete pavement joints. Dowels are subjected to shear and bending stresses caused by traffic loads in addition to curling stresses caused by temperature gradients in pavement slabs. Over time, the use of deicing salts corrodes steel dowels and causes damage to concrete pavement joints. Alternative dowel materials, such as stainless steel and glass fiber-reinforced polymer (GFRP), have been introduced in recent years. The dominant size of dowels for highway pavements has remained the same, typically 38 mm in diameter, and costs can be considerably higher for stainless steel compared with epoxy-coated steel dowels of the same size. Experimental tests at the University of Manitoba, Canada, examined the performance of four dowel types, including the standard 38-mm epoxy-coated steel; 38-mm solid, pultruded GFRP dowels; and 50-mm and 63.5-mm concrete-filled GFRP tube dowels. The dowels were cast in small concrete sl...

Flexural and shear strengthening of timber beams using glass fibre reinforced polymer bars — an experimental investigation

An experimental program was undertaken at The University of Manitoba to test timber stringers strengthened with glass fibre reinforced polymer (GFRP) bars. Various strengthening schemes were investigated as a means of increasing the load carrying capacity of timber stringers in shear and flexure. The shear strengthening was achieved by inserting GFRP dowels in the centre of the cross section along the length of the stringers. The flexural strengthening used the concept of near-surface-mounted GFRP bars. Fifty beams were tested to evaluate the performance of the various strengthening schemes. The behaviour of the beams is described in terms of mode of failure, mechanical properties, and load–deflection behaviour. This study found that strengthening timber stringers with GFRP reinforcement increased the ultimate strength of the stringers and reduced its variability. It is believed that the shear and flexural GFRP reinforcements act as a truss member within the timber beam and bridge the local defects and discontinuities of the timber.Key words: timber, glass fibre reinforced polymer, bridge, stringers, dowels, strengthening, ductility.

Glass Fiber-Reinforced Polymer Dowels for Concrete Pavements

Corrosion of steel dowels in concrete pavements reduces their useful service life and creates considerable maintenance and repair expenditures. Glass fiber-reinforced polymer (GFRP) dowel bars are a possible maintenance-free alternative that will potentially reduce the overall life cycle cost of pavements, especially in corrosive environments. This paper describes the performance of GFRP dowel bars under static and cyclic loads. Dowels were used for a slab/joint model tested under laboratory conditions. This paper also discusses the results of a field application in which 3 types of GFRP dowels were installed in a new concrete pavement highway in Winnipeg, Manitoba, Canada. The field performance of doweled joints has been verified under dynamic load testing.