GFRP Tube Research Articles

Lightweight design to improve crushing behaviour of multi-stitched composite tubular structures under impact loading

This paper presents experimental and numerical studies on the effect of multi-stitching pattern on the energy absorption capability of composite tubular structures under impact loading. A new multi-stitching pattern was developed to study the increase of specific energy absorption capabilities in GFRP and CFRP crash absorbers. The stitching pattern on both specimens showed a significant increase in energy absorption capability under impact loading. According to our results, the specific energy absorption of GFRP and CFRP composite tubes are 17% and 18% higher than non-stitched specimens respectively. A multi-shell finite element model was constructed to predict the axial crushing behaviour and energy absorption capability of composite structures under impact loading. The method is based on an energy-based contact card modelling technique in the stitched and non-stitched area, and the initiation of main central crack growth occurs when the critical separation (PARAM function) is attained, and this represents the functionality of the stitched area during an impact event. The developed numerical approach is efficient in terms of accuracy and simplicity in comparison with the existing methods for multi-layered composites structures.

Strength and ductility improvement of recycled aggregate concrete by polyester FRP-PVC tube confinement

In literature, studies on recycled aggregate concrete (RAC) with recycled aggregates (RAs) originated from clay brick waste are rare, which is mainly attributed to the much lower compressive strength of the RAC with recycled clay brick aggregates (RAC-RCBA) when comparing with its normal aggregate concrete (NAC) counterpart. Nowadays it is well known that fiber reinforced polymer (FRP) composites as lateral confining materials can improve the strength and ductility of NAC significantly. In this study, FRP confining materials were used to improve the compressive strength and ductility of the RAC-RCBA. Compared with conventional synthetic glass or carbon FRP composites, polyester FRP (PFRP) and Polyvinyl chloride (PVC) are much cheaper and show much larger tensile deformation capacity. Therefore, this study investigated the axial compressive behavior of PFRP and PVC hybrid tube encased RAC-RCBA (i.e., shortened as PFRP-PVC-RAC-RCBA) structure. This PFRP-PVC-RAC-RCBA system consisted of an RAC-RCBA core, encased by a PVC tube directly and the PVC tube was further confined with a PFRP tube (i.e. PFRP tube-PVC-RAC-RCBA specimen) or PFRP strips (i.e. PFRP strip-PVC-RAC-RCBA) at the outermost layer. Uniaxial compression tests were performed on 33 PFRP-PVC-RAC-RCBA and 39 unconfined RAC-RCBA specimens to evaluate and compare the axial compressive behavior of PVC tube encased RAC-RCBA, PFRP tube encased RAC-RCBA, PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA columns. The tested variables included the number of PFRP layers (3-, 6- and 9-layer), the type of PFRP confinement (in the configuration of tube or strips) and the spacing of the PFRP strips (25 and 50 mm). The tested results demonstrated that the PFRP-PVC hybrid confining system enhanced the compressive strength and axial and lateral deformations of the RAC-RCBA pronouncedly, e.g. the increase in strength ranged from 4.5% to 39.6%. The enhancement in strength and deformations was increased with a thicker PFRP tube or strip. Both the PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA showed the similar axial compressive stress-stain behaviors. In addition, the comparison of PFRP tube-PVC-RAC-RCBA with the glass/carbon FRP tube-RAC-RCBA indicated that the GFRP and CFRP tube confinement resulted in much larger enhancement in ultimate compressive strength of RAC-RCBA due to the much larger tensile modulus and strength of these G/CFRP composites. However, PFRP-PVC tube confinement led to much larger axial deformation of the RAC-RCBA compared with the G/CFRP tube confinement due to the much larger tensile strain of the PFRP and PVC material. Furthermore, design-oriented compressive stress-strain models were developed for PFRP-PVC-RAC-RCBA specimens.

Experimental assessment and theoretical evaluation of axial behavior of short and slender CFFT columns reinforced with steel and CFRP bars

This paper presents the test results of an experimental program to investigate the structural performance of short and slender concrete-filled fiber-reinforced polymer (FRP)-tubes (CFFTs) columns under pure axial compression load. The test parameters include: transverse reinforcement type (steel spirals versus glass-FRP (GFRP-tube), type of longitudinal reinforcement (steel and carbon-FRP (CFRP) bars), GFRP tube thickness, and slenderness ratio.Comparisons between the experimental test results and the theoretical design equations are performed in terms of ultimate load carrying capacity. The design equation is modified to accurately predict the ultimate load capacities of CFFT columns reinforced with FRP bars. Furthermore, the experimental results showed that the axial compressive strength of CFRP-reinforced CFFT columns was reduced by 22% with increasing the slenderness ratio from 8 to 20. In general, the use of the FRP tube induces a confinement effect for concrete columns which enhances the strength and ductility of such column’s section. This enhancement resulted in a slender section which increased the possibility of buckling instability of the CFFT columns. Thus, a theoretical model was conducted to develop a simplified formula for critical slenderness limit of FRP-reinforced CFFT columns to control the buckling instability mode of failure. Results indicated that the slenderness limit of 14 was suggested as a safe value for the design purposes. A parametric study was conducted which showed the significant effect of the concrete compressive strength and hoop stiffness of FRP tube on the critical slenderness ratio of FRP-reinforced CFFT columns.

Nonlinear Analysis of Bending GFRP Tube Concrete Member

In order to study the factors that influence anti-bending mechanical properties of GFRP tube confined concrete beams and better applied to engineering, the influence of different thickness of GFRP tube, concrete strength grade, the section form and strength of steel were analyzed using finite element analysis software ABAQUS when the beam is in compression condition in this paper. The results showed that the bearing capacity of beams was improved by increasing the GFRP tube thickness, improving the core concrete strength and increasing steel area and strength. The numerical results were in good agreement with the experimental one. The anti-bending bearing capacity formula was in good agreement with the experimental results.

Experimental Research of FRP Composite Tube Confined Steel-reinforced Concrete Stub Columns Under Axial Compression

A new column of FRP composite tube confined steel-reinforced concrete (FTCSRC) column was proposed. This paper elaborates on laboratorial and analytical studies on the behavior of FCTSRC columns subjected to axial compressive load. Eight circular FTCSRC stub columns and one circular steel tube confined concrete (STCC) stub column were tested to investigate the failure mode and axial compression performance of circular FTCRSC columns. Parametric analysis was implemented to inquire the influence of confinement material (CFRP-steel tube or CFRP-GFRP tube), internal steel and CFRP layers on the ultimate load capacity. CFRP-steel composite tube was composed of steel tube and CFRP layer which was wrapped outside the steel tube, while CFRP-GFRP composite tube was composite of GFRP tube and CFRP layer. The test results indicate that the confinement effect of CFRP-steel tube is greatly superior to CFRP-GFRP tube. The ductility performance of steel tube confined high-strength concrete column can be improved obviously by encasing steel in the core concrete. Furthermore, with the increase in the layers of FRP wraps, the axial load capacity increases greatly.

Experimental study on compressive behavior and failure analysis of composite concrete confined by glass/epoxy ±55° filament wound pipes

This paper investigates the strength and ductility of concrete confined by Glass/Epoxy ±55° Filament Wound Pipes (GFRP) under axial compression. A total of 24 cylindrical specimens were prepared with expansive and Portland cements, properly compacted and un-compacted for different composite fresh concrete matrix. Test results showed that compressive strength and axial deformation at failure of concrete confined with GFRP tubes increased by an average of 2.85 and 5.57 times these of unconfined concrete, respectively. Macro and micro analyses of GFRP pipes after failure were also investigated. Debonding, whitening, matrix/transfer cracking, delamination and splitting mechanisms were detected at failure, respectively. The experimental results were also employed to assess the reliability of design models available in the literature for confined concrete compressive strength.

Axial behavior of circular CFFT long columns internally reinforced with steel or carbon and glass FRP longitudinal bars

This paper presents the test results of an experimental study aimed at investigating the behavior of concrete-filled fiber-reinforced-polymer (FRP) tube (CFFT) long columns internally reinforced with longitudinal steel or carbon and glass FRP bars tested under axial compression loading. A total of ten reinforced concrete (RC) and CFFT columns measuring 1900-mm in height and 213-mm in diameter were constructed and tested until failure. The test parameters were: (1) internal reinforcement type and amount; (2) GFRP tube thicknesses; and (3) nature of axial loading (i.e. monotonic and cyclic). The experimental results showed that the GFRP-reinforced CFFT columns had comparable ultimate axial strength and strain capacities compare to their counterparts reinforced with steel bars. As expected, an increase in the FRP tube thickness (or stiffness) resulted in an increase in the strength and strain enhancement ratios. The results also indicated that the residual plastic strain of FRP-reinforced CFFT columns is linearly related to the envelope unloading strain, and this relationship is not influenced significantly by the FRP confinement level but strongly influenced by the internal reinforcement amount and type, particularly when the envelope unloading strain (>0.0035). The presented study showed the applicability of exclusively reinforcing the CFFT columns with FRP bars and subjected to axial compression load. However, further experimental investigations on the axial cyclic behavior of CFFT columns internally reinforced with FRP bars are required to establish such key relationships.

Flexural behavior of U-shape FRP profile-RC composite beams with inner GFRP tube confinement at concrete compression zone

This study investigated the flexural behavior of U-shape hybrid FRP-RC composite beams. The composite beams consisted of U-shape hybrid G/CFRP profile and encased rectangular RC beams with or without inner GFRP tube confinement at concrete compression zone of the beams. A total of 15 medium-sized (i.e. 1800 mm in length, 100 mm in width and 160 mm in depth) beam specimens were constructed and tested under four-point bending, including one ordinary RC beam as reference, 10 hybrid beams with and four hybrid beams without inner GFRP tube confinement. The examined experimental variables included: (1) different arrangements of G/CFRP layer in U-shape FRP profile, (2) inner GFRP tube, (3) conventional steel rebar, and (4) different types of FRP profile and concrete interfacial bond. Based on the testing, the failure mode, load–deflection relationship, ductility, energy absorption capacity and load-strain relationship of the beams were analyzed. The results indicated that compared with the ordinary RC beam, all hybrid FRP-RC beams experienced significant enhancement in cracking, yielding and ultimate loads. The ductility and ultimate load of the composite beams increased with an increase in the thickness of the hybrid FRP profile. The use of GFRP tube at concrete compression zone had a slight increase in the ultimate load of the hybrid beams but resulted in a pronounced enhancement of their ductility. Compared with U-shape FRP profile and concrete interface with a wet-bond type, the gravel-bond type prevented the U-shape FRP profile debonding from the RC beam effectively and in turn improved the yielding load, ultimate load and ductility of the hybrid beams. The hybrid U-shape FRP profile-concrete beams without steel rebar showed the catastrophic brittle failure indicating the necessity of using internal steel rebar for such hybrid beams.

Research on the Influence of Size Effect for the mechanical Performance of GFRP tube concrete steel tube composite column under axial compression

FRP tube-concrete-steel tube composite column (DSTC) was a new type of composite structures. The column consists of FRP outer tube and steel tube and concrete. Concrete was filled between FRP outer tube and steel tube. This column has the character of light and high strength and corrosion resistance. In this paper, properties of DSTC axial compression were studied in depth. The properties were studied by two groups DSTC short columns under axial compression performance experiment. The different size of DSTC short columns was importantly considered. According to results of the experiment, we can conclude that with the size of the column increases the ability of it to resist deformation drops. On the other hand, the size effect influences on properties of different concrete strength DSTC was different. The influence of size effect on high concrete strength was less than that of low concrete.

Nonlinear finite element analysis of short and long reinforced concrete columns confined with GFRP tubes

This paper presents three-dimensional nonlinear finite element models to understand the uniaxial behavior of concrete-filled fiber reinforced polymer tubes. A stress–strain confined model was introduced for the concrete, a damage criteria based on Hashin's failure model was used to model damage and failure of GFRP tubes, and steel bars were modeled based on classic metal plasticity model. A comparison between experimental results found in the literature and the finite element model was conducted regarding the load-deflection curves and the failure pattern of different test specimens. The model was found to be efficient in capturing the loads and deformations of slender concrete-filled fiber reinforced polymer tube columns. It was then used in a parametric study to understand the effect of different parameters (including fiber orientation, number of layers of (glass-fiber reinforced polymer) and steel reinforcement ratio) on the behavior of concrete-filled fiber reinforced polymer tube under axial compressive loading. It was observed that the behavior of the columns was greatly affected by the investigated analysis parameters.

Experimental and Analytical Responses of Hollow and Concrete-Filled GFRP Tube Columns under Impact

AbstractGlass fiber-reinforced polymer (GFRP) composite fender systems, including FRP columns, protect vehicles from colliding with bridge piers. The FRP columns are either hollow (flexible) or fil...

Experimental and Analytical Studies on Compressive Behaviour of Concrete Filled Circular GFRP Tubes

Background/Objectives: An extensive experimental and analytical investigation was carried out to explore the behaviour of circular concrete filled GFRP tubes (CFFTs) using NSC (Normal Strength Concrete), HSC (High Strength Concrete) and UHSC (Ultra High Strength Concrete). Methods/Statistical Analysis: The experimental study explored the compressive behaviour of 27 CFFTs having three different diameters 75, 100 and 150mm of constant thickness 3mm. Un confined concrete strength up to 98 MPa was achieved under normal curing conditions. Findings: The research findings prove that adequately confined high strength CFFTs can exhibit highly ductile behaviour and they are highly sensitive to the level of confinement. The GFRP tubes with UHSC infill could not maintain the load carrying capacity after attaining initial peak strengths. A newer methodology using shell elements was adapted for simulation of CFFTs in ANSYS and the results agreed with that of the experimental investigation. Applications/Improvements: The investigation explored that specimen size does not have major influence on strain reduction factor. New values of strength and strain enhancement ratios K1 and K2 has been arrived.

Finite Element Modeling of Axial Compressive Behaviour of Ultra High Strength Concrete Filled Square and Rectangular GFRP Tubes

Objective: An exploratory research on developing finite element model for studying the axial compressive behaviour of square and rectangular UHSC filled GFRP tubes was conducted. Methods/Statistical Analysis: The well-known fact of deviation in uniformity of confinement in square and rectangular concrete filled GFRP tubes was focused in the nonlinear finite element model. A square and rectangular cross section having same thickness 3mm was chosen keeping two different corner radii 30, and 40mm. The unconfined concrete strength was limited to 120 MPa. The simulation of UHSC filled GFRP tubes were done using ANSYS using elements SOLID 65 for concrete and MEMBRANE 41 for GFRP tube. Findings: The research findings from this investigation on verification by ACI code (ACI committee 440, 2002) revealed that the square CFFTs offer better confinement when compared with rectangular CFFTs and the corner radii significantly affected the ultimate load capacity of the square and rectangular CFFTs. Applications/Improvements: The study has come up with newer method of simulation of GFRP tubes using shell elements assuming perfect bonding between concrete and the tubes. This is the first kind of study in existing FEA database using shell elements. The results agreed with those predicted by the code.

Behavior of glass and carbon FRP tube encased recycled aggregate concrete with recycled clay brick aggregate

In literature, there are few studies which investigated compressive behavior of fibre reinforced polymer (FRP) tube confined recycled aggregate concrete (RAC) where the recycled aggregates (RAs) mainly came from demolished old concrete components. Study which considered FRP tube confined RAC using recycled clay brick aggregates (RCBA) originating from demolished brick masonry components is rare. Thus, this paper reports a systematic study on axial compressive behavior of FRP tube encased RAC containing RCBA (termed as FRP-confined RAC-RCBA). The experimental variables considered are, i.e., replacement ratio of RCBA (r=0, 50, 70 and 100%), FRP tube thickness (nf=2, 4 and 6 layers) and type of fibre material (GFRP and CFRP). This study shows that both GFRP and CFRP tubes enhanced strength and deformation of the confined RAC-RCBA specimens remarkably. The ultimate compressive stress of the confined specimens decreased with an increase of RCBA replacement ratio but their axial deformation kept approximately constant. Failure mode and the compressive stress-strain behavior of G/CFRP-confined RAC-RCBA were similar to these tube confined normal aggregate concrete (NAC) and the ultimate compressive strength of G/CFRP tube confined RAC-RCBA specimens enhanced with an increase in FRP tube thickness. The CFRP-confined specimens showed higher ultimate strength but lower ultimate axial strain than those of GFRP-confined specimens. The applicability of eight widely used confinement models, i.e., 5 design-oriented and 2 analysis-oriented models, for FRP-confined NAC to FRP-confined RAC-RCBA was also evaluated.

The Analysis of the Mechanics Performance about GFRP Tube Confined Concrete Short Column under the Axial Compression

In order to study the axial compression performance of GFRP tube composite columns filled with concrete and better applied to engineering, the influence of different winding angle of GFRP tube, thickness of GFRP tube, concrete strength and the containing rate of steel are simulated by using finite element analysis software ABAQUS when the column under the axial compression ,The results show that: the numerical results are in good agreement with the experimental results; reduced GFRP tube winding angle, increasing the GFRP tube thickness, improve the core concrete strength and an increase in steel containing rate could increase the bearing capacity of columns.

Study on Size Effect of GFRP Tube Concrete Steel Tube Composite Column under Axial Compression

Study on Size Effect of GFRP Tube Concrete Steel Tube Composite Column under Axial Compression

Study on steel reinforced concrete-filled GFRP tubular column under compression

The Steel reinforced concrete-filled fiber reinforced polymer (FRP) tubular column is proposed as a new form of composite column to obtain higher mechanical performance. This paper presents experimental and numerical studies of axially loaded steel reinforced concrete-filled GFRP tubular columns. Ten steel reinforced concrete-filled GFRP tubular columns and two concrete filled GFRP tubular columns are tested. The specimens fail by the rupture of the GFRP tubes under hoop tension and only outward buckling can be observed because of the presence of the concrete core and steel section. Also, the crushed concrete core and buckling of steel section could be observed after removing of the FRP tube. The results indicate steel reinforced concrete-filled GFRP tubular columns have higher specimen stiffness, strength and deformability than concrete filled GFRP tubular columns. A parametric study, including steel ratio and concrete strength, is also carried out.

Experimental and Analytical Studies on Compressive Behaviour of Concrete Filled Circular GFRP Tubes

Experimental and Analytical Studies on Compressive Behaviour of Concrete Filled Circular GFRP Tubes

Axial crush behavior and energy absorption capability of foam-filled GFRP tubes manufactured through vacuum assisted resin infusion process

Foam-filled circular metallic tube has been widely used in safety design of automobile, space craft recovery and so on due to its advantage of high energy absorption. But poor chemical stability and easily oxidized of metal materials seriously threaten the durability and safety of the traditional metallic tube. The application of fiber reinforcement polymer (FRP) can effectively address these issues. In this paper, a simple and innovative foam-filled GFRP tube, fabricated by vacuum assisted resin infusion process, is proposed to enhance the durability and improve the energy absorption capacity. An experimental study was conducted to validate the effectiveness of this kind of absorptor for increasing the energy absorption capacity. Meanwhile, the influences of GFRP skin thickness, diameter of tube, foam density and fiber orientation angle of GFRP mat on failure mode, initial stiffness, stroke efficiency and specific energy absorption were also investigated. An analytical model, considered the confinement effect on foam core and local buckling of GFRP skin, was also developed to predict the ultimate peak strength of foam-filled GFRP tubes. The experimental and analytical results were shown to be well matched.

Compressive behavior of CFFT with inner steel wire mesh

A new concrete filled FRP tube (CFFT) with inner steel wire mesh (WM), termed as CFFT-WM, is proposed in this paper. Uniaxial compression tests were carried out on 27 CFFT-WM specimens to investigate the compressive behavior of the composite structure. The considered experimental variables are number of GFRP layers (1, 2 and 3 layers) and volumetric ratios of WM (0.31, 0.60 and 0.89%). Their effects on the failure mode, compressive stress–strain response, confinement effectiveness and ratio, and the Poisson ratio of the specimens are discussed. The test results show that GFRP tube and WM increase the ultimate compressive strength, strain and ductility of the concrete remarkably. The increase in strength is proportional to an increase in number of GFRP layer. Specimen with higher WM volumetric ratio corresponds to a lower ultimate axial strain but larger strength. In addition, the presence of WM results in a post-peak response showing more ductile compared with the conventional CFFT. Based on the experimental results, confinement stress and strain models were proposed to predict the ultimate compressive behavior of CFFT-WM confined concrete.