Pultruded Tubes Research Articles

Experimental Investigation and Prediction for Bending Creep of Glass Fiber-Reinforced Polymer Pultruded Tube

This study experimentally investigates the bending creep behavior of a pultruded tube made of glass fiber-reinforced polymer (GFRP) and provides the corresponding fitting model as well as the life prediction equation. In the experiment process, the static bending test is performed first to determine the ultimate load-bearing capacities. Then, the creep experiments lasting 3000 h are conducted for GFRP pultruded tubes with 50%, 55%, 60%, and 65% fiber contents, subjected to four different load levels, i.e., 20%, 32.5%, 45%, 57.5%, and 70%, of the ultimate load-bearing capacity. The results indicate that the creep behavior exhibits linear viscoelasticity for load levels below 45%, while the specimens under load levels of 57.5% and 70% experienced creep failure before 1500 h. The test results indicate that for GFRP tubes, the higher the load level, the more pronounced the creep deformation, and specimens with a higher fiber content exhibit better creep resistance compared to those with lower fiber content. When the load level is less than 45%, the creep behavior appears as linear viscoelasticity. However, at a load level of 57.5%, the specimens experience shear failure, and at a load level of 70%, the specimens undergo overall bending failure. In addition, the prediction equation of creep deflection for GFRP pultruded tubes in linear viscoelasticity is developed by utilizing the Bailey–Norton model and the Findley model, and the prediction equation of creep life is acquired by fitting the experimental data with an exponential function.

Innovative Pultruded Composite Mast Design for Railway Overhead Line Structures

The structural feasibility of using a pultrusion of carbon-fibre-reinforced polymers (CFRP) for the lightweight design of a mast for overhead line railway electrification was investigated and simulated. Material characterisation was undertaken using three-point bending and finite element analysis to identify the orthotropic properties of the pultruded tubes designed for a composite mast for overhead electrification. An innovative design of the mast was proposed and verified using a simulation that compared the deflection and stress levels under wind and inertial load. From the simulation results, it was concluded that the proposed composite structure design complies with the mechanical performance requirements for its implementation and benefits the application with a weight reduction of more than 80% with respect to the current steel mast design.

Compressive behaviour of concrete-filled multi-cell GFRP pultruded square columns reinforced with lattice-webs

Experimental studies have generally confirmed the good mechanical performance of the pultruded tubes, while brittle buckling failure and low confining efficiency are still the problems to be addressed. Against this background, a concrete-filled multi-cell glass fibre-reinforced polymer (GFRP) pultruded column reinforced with lattice-webs (ML-CFPT) was proposed, and an experimental study on the compressive behaviour of square ML-CFPTs was presented in this paper. A total of 18 specimens including 6 control specimens and 12 multi-cell columns with/without lattice-webs were tested, with the studied parameters covering the thicknesses of face sheets and lattice-webs. The test results revealed that multi-cell structures improved the brittle failure manner of the pultruded tubes, and applications of lattice-webs delayed the local buckling of pultruded tubes thus exhibiting better confinement effectiveness. Furthermore, a simple design-oriented model on the basis of test results was proposed to predict the bilinear ascending stress–strain curve of the confined concrete in ML-CFPTcs, and the results were consistent with the test data.

Experimental and numerical investigation on the structural performance of a novel type of pultruded composite cross-arm for power transmission towers

In the present paper, a novel type of composite cross-arm for power transmission lines has been introduced. The proposed cross-arm consists of composite pultruded tubes and mechanically bolted joints that form a lattice type of cross-arm structure. Experimental and finite element method (FEM) were used together to obtain the proper design and ensure the ideal performance of the presented cross-arm. Material properties for the composites were experimentally obtained prior to analysis as the input for FEM. Thereafter, non-linear Finite element analysis by using sub-modeling technique and employing progressive damage method was used to predict the failure mode and ultimate failure load for the cross-arm. Verification of the model was carried out by comparison with experimental tensile tests on the mechanically bolted joint of the pultruded tube. Finally, finite element results for the whole cross-arm structure were extracted and the ultimate failure load was predicted. Full-scale tests were also performed on the fabricated cross-arm and the maximum failure load was experimentally achieved. The accuracy of the model was revealed by comparing the results. Good agreement between experimental and FE results were obtained for the failure load. According to the outcomes, the presented composite lattice cross-arm structure is perfectly capable of tolerating applied mechanical loads and can be used as an alternative to conventional steel cross-arms.

WrapToR composite truss structures: Improved process and structural efficiency

Wrapped Tow Reinforced (WrapToR) trusses are ultra-efficient composite structural members that are produced using a novel winding process. In this study, a novel technique is employed during the manufacturing process to improve structural efficiency. By twisting the fibre tow bundle during winding, more consistent shear members were produced that displayed improved buckling resistance. Results from a three-point bend test showed this technique to increase truss failure load by 51% for a particular truss size that is prone to shear web buckling. Comparison of experimental deflections to a previously developed structural analysis tool highlight the importance of capturing deflections due to shear loading. Finally, the truss configuration is experimentally compared to commercially available carbon fibre tubes. When compared to an 8 mm pultruded tube, the truss configuration displayed 9% lower mass, over double the load carrying capability and 6.7 times the flexural rigidity.

Experimental investigation of bond and tube thickness effect on the flexural behavior of concrete-filled FPR tube under lateral cyclic loading

The effect of bond and tube thickness on the flexural behavior of concrete-filled fiber reinforced polymer tube (CFFT) are investigated experimentally in this research. Two different kinds of tubes were used in this research, pultruded tubes and filament winding tubes. Two full scale CFFT column specimens are tested under lateral cyclic load only to study the effect of bond between the concrete core and the tube internal surface under lateral cyclic load only. One of them was prepared with sand-coating on the internal surface of the tube and the other specimen was kept without sand-coating. The CFFT columns were embedded 500mm into a rigid square reinforced concrete footing with 1200mm side dimension and 800mm depth. The two specimens are pultruded FRP tubes having the same mechanical properties and 305mm exterior diameter. Another two full-scale CFFT columns were reinforced with steel reinforcement and were fabricated with tube thicknesses of 4mm and 8mm. These two column were tested to study the tube thickness effect. The columns were embedded 400mm into rigid reinforced concrete footings, which were anchored to the laboratory floor. The columns were loaded under a constant axial load and lateral cyclic load. These two columns are filament winding FRP tubes were manufactured in the Composite Material Reinforcement Laboratory of the Sherbrooke University with the same interior diameter 324mm and with two different thicknesses 4mm and 8mm. The results indicate a significant improvement in the full composite action of CFFT in terms of flexural capacity and stiffness due to the sand-coating. The increasing of the tube thickness delays the yielding of steel and increases the ultimate flexural capacity of the CFFT.

Study of GFRP Steel Buckling Restraint Braces

AbstractBuckling-restraint braces (BRBs) are used extensively in seismic-resistant structures. They consist of a core energy dissipation and external restraining component. A novel glass fiber–reinforced polymer (GFRP) steel BRB is proposed. In the GFRP steel BRB, four GFRP pultruded tubes, which are tied together by GFRP wrapping layers, are used to restrict core steel component buckling instead of conventional steel tube and infilled concrete or mortar. This GFRP steel BRB is extremely lightweight. Techniques for manufacturing GFRP steel BRB were developed for convenient large-scale industrialized production. Quasi-static tests were carried out to validate the performance of the GFRP steel BRB under cyclic loading. The tests focused mainly on energy dissipation capacity and ultimate failure mode of the proposed GFRP steel BRB. The effect of applying additional reinforcements to the GFRP external restraining component on the performance of GFRP steel BRB was also investigated. The performance of the appr...

Energy Absorption of Hybrid Composite Tubes under Axial Compression

The effect of specific absorbed energy on pultruded profile and thin-walled aluminum composite square cross-section tubes were studied via experimentally. The type of strand mat E-glass reinforced polyester resin was conducted in this study. The specimens of square pultruded and thin-walled wrapped strand mat E-glass composite were compressed under quasi-static of obliquely loadings from the top moving plat platen. For each specimen of composite tubes, triggering mechanism was applied on frontal end top of the tube to obtain the progressive failure throughout the crash event. The pultruded profile tube wall-thicknesses of 2.1 mm and thin-walled aluminum 1.9 mm thickness wrapped 3 layer woven fabric were examined, and the effects of crushing behaviors and failure modes were discussed. Results showed that the tubes energy absorption capability was affected significantly by different type of composite made in term of internal energy.

Crushing Behavior of Hybrid Foam-Filled Pultruded Composite under Quasi-Static Oblique Loading

In this present paper, the two square cross-section pultruded composite tubes E-glass reinforced polyester unfilled and polyurethane hybrid foam-filled subjected to oblique load are investigated and examined experimentally. The oblique angles were varied from 5 to 20 with an increment of every 5 degree. The bottom base platen of clamped specimen was adjusted inclination angle of loading direction with respect to the tube axis. During the experimental observation, three characteristic crushing stages were identified as initial peak load stage, progressive crushing stage and compaction zone stage. The pultruded composite tube wall-thicknesses of at 3 mm were examined, and the effects of crushing behaviors and failure modes were analyzed and discussed. Results showed that the tube’s energy absorption capability was affected significantly by varying of oblique loading. It is also found that as the filling polyurethane foam into pultruded E-glass reinforced polyester composite square tube increases the amount of specific absorbed energy than the empty tubes.

Damage modelling of repeatedly impacted square fibre-reinforced polymer composite tube

This paper proposed a lifetime prediction model to characterise the damage response of square fibre-reinforced polymer (FRP) composite tubes under repeated axial impact. The model, which is a function of damage parameter D and normalised impact number Nf, used an energy-based approach. Series of impact and quasi-static compressive tests on composite tubes were undertaken to determine the required parametric values and to validate the reliability of the proposed model. Testing was performed by axially impacting 100mm FRP pultruded tubes to 130 repeated impacts or up to collapse using a drop-mass type impact apparatus. The quasi-static compressive test was conducted using a 2000kN capacity servo-hydraulic compressive testing machine. Results showed that the impact fatigue curve of the composite tubes follows a power function relationship. The variation of incident energies Ein between the fitting curve and experimental data is less than 3%. A good agreement is observed between the experimental data points and the prediction model.

Experimental investigation on the behaviour of square FRP composite tubes under repeated axial impact

Series of impact tests were conducted to investigate the behaviour of fibre reinforced polymer (FRP) composite tubes under axial impact. The effects of damage parameters such as the mass of the impactor, incident energy and number of impacts on their behaviour were studied. The tests were performed by axially impacting 100mm square FRP pultruded tubes to 130 repeated impacts or up to collapse using a drop-weight type impact apparatus. Impact masses and drop heights were varied to produce incident energies ranging from 158 to 635J. The results showed that the peak load degradation of collapsed tubes is more rapid when it is impacted by higher incident energy. Heavier impactors caused more damage to the tubes at lower incident energies as reflected by their lower number of impacts to collapse, however, its effect gradually decreases at relatively higher energies. The incident energy is a major damage factor in the collapse of the tubes for lower number of impacts. However, the number of impacts becomes the key factor when the value of the incident energy decreases.

Residual properties of square FRP composite tubes subjected to repeated axial impact

In this paper, the residual properties of square composite tubes under axial impact were experimentally investigated. The effects of damage factors such as the mass of the impactor, incident energy, and number of impacts on their post-impact behaviour were emphasised. Low-velocity impact tests were performed by repeatedly impacting a 100mm square FRP pultruded tube with energy levels up to 742J using a drop-weight apparatus. Coupons were then taken from the impacted tubes and tested statically to determine the residual compressive, tensile, and flexural properties. Results show that the levels of impact energy, number of impacts, and the mass of the impactor significantly influenced the residual strength degradation of the impacted tubes. Their effects, however, are almost negligible in the residual modulus property. It was found that the maximum reductions of residual compressive, tensile, and flexural strengths of the impacted tubes are 6.8%, 0.3%, and 10%; respectively. It was also found that effect of impact damage on the reduction of residual compressive strength of the tube is concentrated only in region closer to the impact point.

Global Restraint in Ultra-Lightweight Buckling-Restrained Braces

A concept for an ultra-lightweight buckling-restrained brace was conceived, and a prototype was designed that utilized an aluminum core and bundled glass fiber-reinforced polymer pultruded tubes for the buckling restraint. Prediction of global stability in compression was made using analytical methods based on single-degree-of-freedom (SDOF) and previously established Euler buckling models. Detailed finite-element simulations of the proposed prototypes utilized a constitutive model calibrated from experimentally obtained reversed cyclic coupon testing of 6061-T6511 aluminum alloy at 2–4% total strain amplitude. Analytical formulations were compared with monotonic and cyclic numerical results from a parametric study varying restrainer stiffness, end moments induced by frame drift, and core reduced section length. The study concluded that SDOF and Euler formulations may underestimate the required restrainer stiffness by a factor of two or greater. The resulting ultra-lightweight brace prototypes satisfying global buckling restraint were calculated to weigh 27 and 41% of traditional mortar-filled tube and all-steel buckling-restrained brace (BRB) configurations, respectively.

Crushing Behaviors and Energy Absorption Efficiency of Hybrid Pultruded and ±45° Braided Tubes

A numerical and experimental investigation was carried out to evaluate the response and energy absorbing capacity of hybrid composite tubes made of unidirectional pultruded tube over wrapped with ±45° braided fiber-reinforced plastic (FRP). The numerical simulation characterized the crushing behaviors of these tubes subject to both quasi-static compression and axial dynamic impact loadings. Two types of FRP braids, that is, glass and carbon fibers braids were considered. Parametric studies were also conducted to examine the influence of the thickness and type of braid, as well as the loading conditions on the crushing behavior of the tubes. Due to its ease and controllability, quasi-static crushing tests were conducted to verify the numerical studies’ findings. Very good agreement was observed between the finite element simulation and experiments. It was observed that the presence of braids restrained the brittle crack propagation in pultruded tubes, thus reinforced the flexural behavior of the tube walls, and in turn improved their energy absorption capacity. Moreover, the hybrid tubes exhibited a more desirable, accordion type failure mode, therefore they are considered to be more suitable candidates as energy absorbing structural members in service conditions.

Gridshell structures in glass fibre reinforced polymers

Applications in which composite materials are used as bearing structural elements are rare and generally copy structural solutions that have been optimized for steel for years. Unfortunately these materials have very different properties, therefore specific construction methods and specific structural forms have to be invented for composite materials. Gridshell structures may be one of those. So, after a brief history of gridshells, a demonstration with the Ashby’s method that glass fibre reinforced polymers are an alternative for this kind of structure is shown. An original experimental test for the identification of the parameters of the short and long time behaviours of bent pultruded tubes is then detailed. Afterwards a scale one prototype of composite gridshell is presented and loaded. Results of the experimental tests are compared to numerical results of a non-linear analysis done with the dynamic relaxation method. The authors then concluded on the feasibility of such composite gridshells and on their potential for future development.

Performance Evaluation of FRP Composite Deck Considering for Local Deformation Effects

We examine here the replacement of a deteriorated concrete deck in the historic Hawthorne Street Bridge in Covington, Va. with a lightweight fiber-reinforced polymer (FRP) deck system (adhesively bonded pultruded tube and plate assembly) to increase the load rating of the bridge. To explore construction feasibility, serviceability, and durability of the proposed deck system, a two-bay section (9.45 by 6.7 m ) of the bridge has been constructed and tested under different probable loading scenarios. Experimental results show that the response of the deck is linear elastic with no evidence of deterioration at service load level (HS-20). From global behavior of the bridge superstructure (experimental data and finite- element analysis), degree of composite action, and load distribution factors are determined. The lowest failure load ( 93.6 kips or 418.1 kN ) is about 4.5 times the design load ( 21.3 kips or 94 kN ), including dynamic allowance at HS-20. The failure mode is consistent in all loading conditions ...

A numerical study on the axial crushing response of hybrid pultruded and ±45° braided tubes

Abstract A comprehensive numerical investigation was carried out to evaluate the response and energy absorbing capacity of hybrid composite tubes made of unidirectional pultruded tube over wrapped with ±45° braided fiber-reinforced plastic (FRP). The numerical simulation characterized the crushing behaviors of these tubes subject to both quasi-static compression and axial dynamic impact loadings. Two types of braided FRP, glass and carbon fibers, were considered. Parametric studies were also conducted to examine the influence of the tube’s length, thickness and type of braid, as well as the loading conditions on the crushing behavior of the tubes. It was observed that although the pultruded tube, which had the highest stiffness among the tubes considered, produced the highest magnitude of energy absorption capacity, it exhibited a non-symmetric failure mode followed by a longitudinal splitting. On the other hand, the hybrid tubes exhibited a more desirable, accordion type failure mode, therefore they are considered to be more suitable candidates as energy absorbing structural members in service conditions.

Fatigue Behavior of Prestressed Tubular Bridge Deck of Fiber-Reinforced Polymer

An experimental study was undertaken to assess the flexural fatigue performance of a new deck system of fiber-reinforced polymer (FRP) that has been installed on a bridge in Delaware County, Ohio. The deck consists of a series of 4-in. (102-mm) square pultruded FRP tubes with a thickness of 1/4 in. (6.4 mm), laid side by side on existing stringers, perpendicular to the direction of traffic. The tubes are posttensioned up to 20 kips (90 kN) with 0.6-in. (15-mm) diameter seven-wire strands at midpoints between the stringers in the direction of traffic. Four double-span FRP deck specimens with two different tube sizes and three different span lengths were tested in flexural fatigue under AASHTO-prescribed footprint of wheel loads for an HS20 truck. Panel action in the deck system was inadequate for the most part, as only the tubes that were directly under the load carried the majority of the load. Subsequent slippage between these tubes and their adjacent tubes can cause cracking in the asphalt overlay. However, no such crack has been observed on the actual bridge after 1 year in service. Panel action is generally improved at higher prestress levels. Prestressing also offers additional redundancy and reserve strength for the system. While longer span decks fail in bending, shorter span decks generally suffer from local shear failure as a result of stress concentrations at the corner of the tubes under the applied load or at the support. The fatigue problem is less critical for longer span decks and smaller tube sizes.

Testing and Evaluation of Components for a Composite Bridge Deck

In this paper the results of an experimental investigation conducted on 76 mm (3 in) square hollow pultruded glass fiber-reinforced polymer (GFRP) tubes and their assemblies have been discussed. These GFRP tubes are used in the fabrication of an all-composite bridge deck that is designed for H-20 truckloads as specified by the American Association of State Highway and Transportation Officials (AASHTO). The study is principally focused on the experimental characterization of flexure performance under static loading of pultruded GFRP tubes made of unidirectional glass fibers. Several tests were conducted on single GFRP tubes followed by combinations of two tubes and a four-layered tube assembly. The tubes were bonded together using epoxy adhesive to build the assembly. The specimen details, experimental setup and instrumentation, testing procedure, failure modes and the test results of these experiments have been discussed in detail. A preliminary design model of each test coupon was developed and analyzed using Finite Element Analysis (FEA). Experiments were conducted to corroborate the analytical design model. Comparison between the theoretical and experimental results showed good correlation. Experimental results show excellent linear elastic flexural and shear behavior up to failure. The stiffness of the tubes and their assemblies demonstrate that they can be used in the building of all-composite bridge decks and for other infrastructure applications. Failure modes for the samples under static flexural loads are described.

Finite element analysis of FRP tube assemblies for bridge decks

Fiber reinforced polymer (FRP) composite materials have many advantages over traditional building materials. They are becoming more and more popular in civil engineering applications. FRP pultruded tubes are easy to fabricate and can be easily assembled for different applications. In this paper, FRP tube assemblies of variable size, fiber material, tube wall thickness, and different installation are studied using finite element analysis. The deflection and stress distribution are listed for each case. When compared to experimental results, the numerical analysis shows good correlation. Data gained in this study can be used for design and optimization of FRP tube assemblies for bridge deck construction and similar applications in civil engineering.