GFRP Tube Research Articles

Study on Axial Compression Performance of GFRP Tube Reactive Power Concrete Composite Short Columns with Encased Steel

In order to study the axial compression performance of the GFRP tube reactive power concrete composite short column with encased steel, a finite element model of the composite short column was established. The constitutive models of steel, RPC and GFRP were selected. The element selection and contact method of each component were explained. The boundary condition and mesh division of the composite column were determined. Based on this, finite element verification analysis of 6 specimens was performed by ABAQUS. The load-displacement curves and the axial compression bearing capacity were obtained. By comparing with the test, the reasonability of the constitutive model and the finite element model of this kind of column is verified.

Behavior of FRP-HSC-steel tubular columns under axial compression: A comparative study

In this study, the compressive behavior of FRP-concrete-steel double-skin tubular columns (DSTCs) and double-tube concrete columns (DTCCs) with HSC and NSC, as well as the concrete-filled steel tubular (CFST) columns and concrete-filled FRP tubular (CFFT) columns with HSC and NSC, were comprehensively studied and compared, with the CFST columns and CFFT columns working as the reference specimens to better investigate the failure mechanism of DSTCs and DTCCs. The failure mode, load-deformation characteristics, dilation behavior, strain distribution in GFRP and steel tube were presented and analyzed. In addition, the failure mechanisms, axial stiffness and ductility, composite effect (in terms of load-carrying capacity) have been compared and discussed in depth in this paper, based on which a design approach of the DSTCs and DTCCs using HSC can be developed in the future. It was found that the composite effect may be found in DTCC columns but not in the DSTCs due to the effect of local buckling of steel tube in the latter.

Test on residual ultimate strength of pultruded concrete-filled GFRP tubular short columns after lateral impact

This paper presented the experimental investigations and numerical analyses on the compressive behavior of pultruded concrete-filled GFRP tubular (CFGT) short columns after lateral impact. Taking the thickness of GFRP tube, concrete compressive strength, impact height, and impact location as influential factors, 117 CFGT short columns were tested under axial compression, including 108 specimens after lateral impact and 9 specimens without impact. Tear-up and Tear-up included local buckling were two main failure characteristics of specimens under axial compression. Test results indicated that the increase of thickness of GFRP tube remarkably enhanced the residual ultimate strength of specimens subjected to lateral impact. The impact height exerted negative effects on the residual ultimate strength and axial stiffness of the CFGT short columns. The residual ultimate strength of the specimens decreased significantly as the impact height increased, especially for the thin-walled specimens. However, the impact location only showed a limited influence on the residual ultimate strength of CFGT short columns. According to the experimental results and theoretical analyses, the design formulas were proposed to estimate the residual ultimate strength of CFGT short columns after lateral impact.

Behaviour of FRP-confined coal rejects based backfill material under compression

This paper introduces a novel standing support incorporating fibre-reinforced polymer (FRP), termed FRP tubular standing support (FTSS). The exterior container of FTSS is the small rupture strain (SRS) GFRP tube wrapped with ultra-high molecular weight polyethylene (UHMWPE) FRP jacket with large rupture strain (LRS), while the infill is the coal rejects based backfill material (CBM). The CBM is made of industrial by-product (i.e. coal rejects) and high flowable cementitious grout material, leading to some environmental and economic benefits when it is used in underground mines. Test variables included the type of coal rejects (i.e. screened and unscreened), the thickness of SRS FRP tube (i.e. 1.5 mm and 3.0 mm) as well as the thickness of LRS FRP jacket (i.e. 2-ply, 3-ply and 4-ply). Test results showed that both the load carrying capacity and deformation ability of CBM in FTSS have been significantly enhanced attributed to the confinement provided by exterior FRP container. Existing stress–strain model for FRP-confined normal concrete can be used to reasonably predict the compressive behaviour of confined CBM in FTSS with large deformation ability. The ductile FTSS is suitable for underground spaces and infrastructures where the integrity of structure is the main concern.

Test on mechanical behavior of pultruded concrete-filled GFRP tubular short columns after elevated temperatures

This paper presents an experimental investigation on the mechanical behavior of pultruded concrete-filled GFRP tubular (CFGT) short columns exposed to elevated temperatures under axial compressive loading. A total of 117 pultruded CFGT short columns subjected to different elevated temperatures and temperature duration were axially tested, including 108 specimens after elevated temperature and 9 specimens at ambient temperature served as the control group. The main variables explored in this paper included the GFRP tube thickness, concrete compressive strength, elevated temperature, and temperature duration. The results obtained from the experiments indicate that the ultimate strength and initial stiffness of specimens decrease remarkably with the increase of the elevated temperature, while the ductility of specimens is enhanced accordingly. Especially, the elevated temperature causes an obvious reduction (about 37%) in the ultimate strength of specimens when it exceeds 200 °C. Among the four main variables, the elevated temperature exerts the most significant impacts on the ultimate strength of specimens, the GFRP tube thickness and concrete compressive strength have certain positive effects, while the influence of temperature duration is almost negligible. Based on the experimental results, a parameter formula for the calculation of the ultimate strength of pultruded CFGT short columns after elevated temperatures is proposed, which shows great accuracy and rationality compared with the test results.

Axial monotonic and cyclic compressive behavior of square GFRP tube–confined steel-reinforced concrete composite columns

Fiber-reinforced polymer tube–confined steel fiber–reinforced concrete column is a novel composite column proposed recently, which consists of a traditional steel-reinforced concrete column and an external glass fiber–reinforced plastic tube for lateral confinement. In order to investigate the axial compression behavior of steel fiber–reinforced concrete columns, a total of 16 square specimens were fabricated and tested under axial monotonic and cyclic compressive loading. Three different configurations of inner shaped steels, including cross-shaped, box-shaped with wielding, and box-shaped without wielding were considered. Two thicknesses of glass fiber–reinforced concrete tubes were also considered as the main experimental parameters. On the basis of test results, a thorough analysis of the failure process based on strain analysis was discussed. The test results showed that steel fiber–reinforced concrete columns exhibited higher ductility and load capacity compared with fiber-reinforced plastic–confined plain concrete columns. Two quantitative indexes were proposed to measure the confinement of steel fiber–reinforced concretes. The axial cyclic mechanical behaviors were discussed through comparative analysis with monotonic behaviors. The remnant strains and modulus of the cyclic behaviors were also discussed.

Effect of hygrothermal ageing on the compressive behavior of glass fiber reinforced IPN composite pipes

The influences of hygrothermal ageing on the compressive behavior of the glass fiber reinforced interpenetrating polymer network (IPN) composites were discussed. Specimens with different proportions of polyurethane (PU) prepolymer with Vinylester (VER) were fabricated by hand – layup technique then the tubes were hygrothermally aged in water at different temperatures of 55 °C, 65 °C, 75 °C for periods of 500, 1000, 1500, 2000 h. Uniaxial compressive tests were performed on the dry and aged sample by using a universal testing machine as per the ASTM D695-10 standard in room temperature to absorb the response of the tubes at standard temperatures. The relationships between the dry specimens with the aged specimens were determined. The absorbed results shown that the strength of the GFRP tubes slightly decreases with increase of the temperature and with respect to corresponding ageing period. Further the geometric structure of the specimen retains, as much as % of PU prepolymer increases into the IPN system.

Experimental study on compressive behavior of concrete-filled GFRP tubular stub columns after being subjected to acid corrosion

This paper presents the results of axial compression tests of concrete-filled GFRP tubular (CFGT) stub columns after being subjected to acid corrosion. Fifty-four specimens subjected to acid corrosion and nine specimens untreated with acid solutions are axially tested. The main parameters considered in this study include the wall thickness of GFRP tube, concrete strength, PH value of acid solution, and immersion duration. CFGT stub columns after being subjected to acid corrosion are all failed with the fracturing of GFRP tube and crushing of core concrete. The ultimate strength of the CFGT stub columns corroded by acid solution decreases remarkably compared with those without acid corrosion. The longer the immersion duration, the lower the ultimate strength of the acid corroded CFGT stub columns. Immersion duration has the greatest influence on the percentage decrease of ultimate strength of the acid corroded CFGT stub columns, followed by the PH value of acid solution. However, the effects of the wall thickness of GFRP tube and concrete strength on the percentage decrease of ultimate strength can be neglected. Additionally, the finite element models are also developed for the acid corroded CFGT stub columns by the ABAQUS software and are verified with the experimental results.

브레이딩 GFRP 튜브로 구속된 원형 CFT의 압축강도 예측식 제안

강관과 FRP tube로 구속된 콘크리트는 외부 FRP가 강관의 부식을 방지하고 심부에 추가적인 구속압을 제공하여 콘크리트의 압축강도를 증가시킬 수 있는 구조로 되어있다. 구속효과는 강관과 FRP tube로 구속된 콘크리트 압축설계의 주요 설계요소이다. 그러나, 강재와 FRP의 조합된 구속효과를 고려한 콘크리트 압축설계기준은 현재까지 정립되지 않았다. 따라서 이 연구에서는 실험적 분석을 통해 강관과 GFRP tube로 구속된 콘크리트의 압축강도 예측식을 제안하였다. 이 논문은 강관과 직조 브레이딩 유리섬유복합체 튜브로 구속된 콘크리트의 압축실험 결과를 제시하고 있다. 압축실험의 변수는 GFRP 튜브의 두께(0, 2, 4, 6 ㎜)로 하였다. 실험 결과, CCFT의 압축강도는 GFRP 튜브의 두께와 비례하게 증가하는 것으로 나타났다. CCFT의 압축강도 예측식은 실험 결과를 분석하여 제시하였다. 이 연구에서 제안한 예측식과 선행 연구의 예측식을 통해 분석한 CCFT의 압축강도는 실험의 결과와 비교, 분석하였다.

Monitoring of Interfacial Debonding of Concrete Filled Pultrusion-GFRP Tubular Column Based on Piezoelectric Smart Aggregate and Wavelet Analysis.

The concrete filled pultrusion-GFRP (Glass Fiber Reinforced Polymer) tubular column (CFGC) is popular in hydraulic structures or regions with poor environmental conditions due to its excellent corrosion resistance. Considering the influence of concrete hydration heat, shrinkage, and creep, debonding may occur in the interface between the GFRP tube and the concrete, which will greatly reduce the cooperation of the GFRP tube and concrete, and will weaken the mechanical property of CFGC. This paper introduces an active monitoring method based on the piezoelectric transducer. In the active sensing approach, the smart aggregate (SA) embedded in the concrete acted as a driver to transmit a modulated stress wave, and the PZT (Lead Zirconate Titanate) patches attached on the outer surface of CFGC serve as sensors to receive signals and transfer them to the computer for saving. Two groups of experiments were designed with the different debonding areas and thicknesses. The artificial damage of CFGC was identified and located by comparing the value of the delay under pulse excitation and the difference of wavelet-based energy under sweep excitation, and the damage indexes were defined based on the wavelet packet energy to quantify the level of the interface damage. The results showed that the debonding damage area of CFGC can be identified effectively through the active monitoring method, and the damage index can accurately reflect the damage level of the interface of GFRP tube and concrete. Therefore, this method can be used to identify and evaluate the interface debonding of CFGC in real time. In addition, if the method can be combined with remote sensing technology, it can be used as a real-time remote sensing monitoring technology to provide a solution for interface health monitoring of CFGC.

Durability of pultruded GFRP tubes subjected to seawater sea sand concrete and seawater environments

This paper presents a study on the durability of pultruded GFRP tubes subjected to seawater sea sand concrete (SWSSC) and seawater environments. Environmental conditions, time and temperature of conditioning, and the tube thickness were the studied parameters. Tensile and compressive strength tests were conducted to investigate the mechanical properties of tubes after conditioning. SEM and micro-CT were used to investigate the microstructural properties, degradation mechanisms and damage levels. Finally, models were proposed to predict the long-term performance of GFRP tubes under different conditions using Arrhenus theory. The results showed that SWSSC is significantly harsher condition for GFRPs compared to seawater. A reduction factor is recommended for tensile strength and compressive strength of GFRP tubes exposed to SWSSC and seawater environments.

An integrated approach of form finding and construction simulation for glass fiber‐reinforced polymer elastic gridshells

SummaryGlass fiber‐reinforced polymer (GFRP) elastic gridshell is composed of long continuous GFRP tubes and achieves its shape through the elastic deformations during the lifting construction process. However, the complicated mechanical behaviors during the practical forming process are rarely examined in the previous researches. In this research, an innovative approach consolidating the form‐finding analysis and the construction simulation is proposed for the GFRP elastic gridshells. The integrated approach, which is developed with the ABAQUS and Python, is based on finite element analysis and iterative optimization; therefore, the mechanical deformations of gridshell can be accurately taken into account. The procedure of the integrated analysis is comprehensively presented by taking a typical double‐hump gridshell as an example. The form‐finding results (i.e., the flat lattices) derived from the iteration are found to be insensitive to the initial input. The structural behavior indexes (e.g., deflections, support reactions, and sectional stresses) during the lifting construction process are also available in the analysis. Based on the indexes, some general structural features of such gridshells are concluded. The achievements provide novel perspectives for the form‐finding analysis of GFRP elastic gridshells where lifting construction is involved, which is beneficial for the design and analysis of such structures.

Experimental results of circular FRP tube confined concrete (CFFT) and comparison with analytical models

This study experimentally investigates the axial compressive behavior of Carbon Fiber Reinforced Polymer Tube Confined Concrete (CFRP CFFT) and Glass Fiber Reinforced Polymer Tube Confined Concrete (GFRP CFFT) specimens. The experimental results demonstrate significant improvement in the axial stress-strain behavior of CFRP CFFT and GFRP CFFT specimens with an increase in thicknesses of CFRP tubes and GFRP tubes, respectively. The axial stress-strain (fc−εc) curves of CFRP CFFT and GFRP CFFT specimens were constructed using well-known stress-strain models for Fiber Reinforced Polymer confined concrete. The fc−εc curves of CFRP CFFT and GFRP CFFT specimens constructed using the Samaan et al. [1] model mapped well with the corresponding experimental fc−εc curves, whereas fc−εc curves constructed as per the Lam and Teng [2] model exhibited a reasonable match with the corresponding experimental fc−εc curves. The fc−εc curves of CFRP CFFT and GFRP CFFT specimens constructed based on ACI 440.2R-08 [3] considerably underestimated the experimental axial stresses and axial strains. A parametric study was carried out to examine the effects of actual confinement ratio and type of FRP tube confinement on the fc−εc curves of CFFT specimens. It was found that actual confinement ratio and type of FRP tube confinement significantly influence the axial stress versus axial strain curves of CFFT specimens.

Technical note on compressive behaviour of CNT-reinforced concrete filled GFRP tubes

This analytical study explores the utilization of CNTs as fiber reinforcements in GFRP tube confined concrete columns using finite element analysis software ANSYS. The CNT- reinforced concrete columns were confined with GFRP tubes of fiber orientation ±85°. The tube thicknesses chosen were 3 mm and 4 mm with the slenderness ratios of CFFTs being 2,4,6,8,12,16 along CNT reinforcement of 1%, 2%, and 3%. Three grades of concrete 40 MPa (Normal Strength Concrete), 60 MPa (High Strength Concrete), and 120 MPa (Ultra High Strength Concrete) had been chosen. About 144 GFRP tube confined CNT reinforced Concrete columns were simulated using ANSYS software covering NSC, HSC and UHSC and their stress strain behavior, failure modes, effect of confinement, slenderness ratio, thickness of GFRP tubes and the fiber volume fraction of CNTs had been investigated and reported. The slenderness ratio 6 was optimal for CNT reinforced concrete columns confined with GFRP tubes. The strength enhancement of CNT reinforced UHSC was about 2.6 times of CNT reinforced HSC. The passive confinement provided by the FRP jacket loses its effectiveness on increasing the grade of concrete particularly the Ultra High Strength Concrete. This led to brittle failure. However the axial strength enhancement reached a peak when compared with other grades of concrete.

GFRP管–钢骨混凝土纯弯构件的滞回性能研究

GFRP管–钢骨混凝土纯弯构件的滞回性能研究

Test on axial compression performance of nano-silica concrete-filled angle steel reinforced GFRP tubular column

AbstractThis paper attempts to investigate the effect of various parameters on the axial compressive behavior of nano-silica concrete-filled angle steel reinforced GFRP tubular columns. The proposed new composite column consists of three parts: the outer GFRP tube, the inner angle section steel and the nano-silica concrete filled between GFRP tube and angle section steel. Twenty-seven specimens with different nano-silica concrete compressive strength (20MPa, 30MPa and 40MPa), diameter-to-thickness ratio of GFRP tube (20, 25 and 40) and steel ratio (0.008, 0.022 and 0.034) were tested under axial load. The main purpose of this study is to examine the effect of the three parameters on the following: failure modes, deformation capacity, load bearing capacity, ductility and initial stiffness of the new composite column under axial load. It was found that the load bearing capacity and initial stiffness increased as the nano-silica concrete compressive strength of the specimens increased. But the specimens with higher nano-silica concrete compressive strength showed lower deformation capacity than that of the specimens with lower nano-silica concrete compressive strength. The varieties of the steel ratio have no significant effect on the specimens’ axial deformation behavior. Experimental results also showed that both load bearing capacity and deformation capacity increased with the decrease of diameter-to-thickness ratio of GFRP tube. However, diameter-to-thickness ratio of GFRP tube has no significant effect on the initial stiffness of specimens. The confinement coefficient was proposed to better evaluate the confinement effect of GFRP tube on the inner angle section steel reinforced core nano-silica concrete. The confinement effect of GFRP tube on lower strength concrete was better, and the confinement effect reduced as the diameter-to-thickness ratio of GFRP tube increased. The design formulas for the load bearing capacity of the nano-silica concrete-filled angle steel reinforced GFRP tubular columns under axial load were proposed.

Experimental study on hollow steel-reinforced concrete-filled GFRP tubular members under axial compression

Hollow steel-reinforced concrete-filled GFRP tubular member is a new kind of composite members. Firstly set the mold in the GFRP tube (non-bearing component), then set the longitudinal reinforcements with stirrups (steel reinforcement cage) between the GFRP tube and the mold, and filled the concrete between them. Through the axial compression test of the hollow steel-reinforced concrete-filled GFRP tubular member, the working mechanism and failure modes of composite members were obtained. Based on the experiment, when the load reached the ranges of 55-70%Pu (Pu-ultimate load), white cracks appeared on the surface of the GFRP tubes of specimens. At that time, the confinement effects of the GFRP tubes on core concrete were obvious. Keep loading, the ranges of white cracks were expanding, and the confinement effects increased proportionally. In addition, the damages of specimens, which were accompanied with great noise, were marked by fiber breaking and resin cracking on the surface of GFRP tubes, also accompanied with concrete crushing. The bearing capacity of the axially compressed components increased with the increase of reinforcement ratio, and decreased with the increase of hollow ratio. When the reinforcement ratio was increased from 0 to 4.30%, the bearing capacity was increased by about 23%. When the diameter of hollow part was decreased from 55mm to 0, the bearing capacity was increased by about 32%.

Behaviour of column constructed with FRP tubes filled with concrete

This paper investigates the behaviour of Concrete-Filled FRP Tubes (CFFT) as columns. The experimental programme consists of preparing and testing one steel column acting as control sample and three columns made with GFRP. The GFRP tubes were produced by filament winding method where the amount and orientation of the fibres was changed. The tubes had dimensions of 1000x100 mm (length x diameter) and were filled with C25/30 concrete. The columns were tested under compression and the load was applied at a pace rate of 0.5 mm/min. It was found that the GFRP tubes can efficiently confine the concrete and could be used as alternative material to steel tubes. The steel and GFRP samples developed a high level of strain throughout the testing. The GFRP sample with fibre orientation of 90° failed by FRP rupture, whereas the remaining samples failed by buckling. The orientation of the fibres at 90° was more efficient than orientation of fibres at 45° in terms of increasing the ultimate capacity. The GFRP samples displayed lower ultimate capacity compared to steel samples with same wall thickness, but increasing the wall thickness of the GFRP columns increased the ultimate load accordingly.

A Feasibility Study on GFRP Tubular Concrete Column Damage Detection Using Piezoceramic-transducer-enabled Active Sensing

Aiming at the crack damage of concrete in GFRP tubular concrete column, a method based on piezoelectric wave method was developed to monitor the crack damage. By transmitting and receiving stress waves from a pair of piezoelectric ceramic sensors embedded in GFRP tubular concrete, the damage degree of GFRP tubular concrete columns was evaluated by using wavelet packets to obtain the stress wave energy and damage index under different load levels. By analyzing the change of stress wave energy and damage index of concrete with different strength under different loads, the time-domain signal response, load-energy curve and load-damage index curve were obtained. In this test, four test pieces were designed according to different concrete strength grades. Two piezoelectric ceramic sensors were placed in the test piece and used to monitor the test piece under static loading. After the static loading was completed, the GFRP tube was severely broken and peeled off from the concrete. A large number of cracks appeared on the concrete surface. The results show that: The test results were consistent with the actual damage of the specimen. The development trend of concrete damage in GFRP tubular concrete columns was well revealed by the wave method.

空实心GFRP管钢筋混凝土偏心受压构件徐变分析

空实心GFRP管钢筋混凝土偏心受压构件徐变分析