GFRP RC Research Articles

Investigation of Strut-and-Tie Model Performance Using Symmetrically Loaded GFRP–RC Double Corbels

Investigation of Strut-and-Tie Model Performance Using Symmetrically Loaded GFRP–RC Double Corbels

Experimental Investigation of Ductility in GFRP RC Beams by Confining the Compression Zone

Nowadays, building structures in corrosive environments requires some considerations. Being lightweight, high tensile strength, and corrosion resistance are the features that make fiber-reinforced plastic (FRP) bars an alternative component for longitudinal steel reinforcement of concrete. On the other hand, the linear elastic behavior of FRP bars, alongside the brittle behavior of concrete, makes brittle members without considerable ductility. In this paper, the effect of compression region confinement with CFRP sheets on the FRP-reinforced concrete beams was experimentally investigated. Eight GFRP reinforced beams with 2 m length, including one reference beam and seven confined beams, were constructed and tested under a four-point bending test. Based on the type of confinement, specimens are categorized into four groups. Flexural behavior improvements, including load carry capacity, energy dissipation capacity, and ductility, were observed in at least one specimen of each confined group. According to the results, the specimen that was spirally confined with a 30 mm ribbon width and angle of 10° had the best total energy absorption up to about 110% improvement in comparison to the unconfined specimen. On the other hand, vertically confined specimens with 50 mm ribbon width showed the highest improvement in ductility indices and load carrying capacity up to 60% and 11% in comparison to unconfined specimens, respectively. Due to concrete compression zone fractures in flexural failure mode, the over-reinforce method is considered the design philosophy. Results indicate that regardless of the confinement type (discrete vertical, discrete spiral, or continuous spiral confinement), there is an optimal amount for width, blank space between ribbons, and depth of confinement to achieve the best flexural behavior.

Effect of BFRP ties on the axial performance of RC columns reinforced with BFRP and GFRP rebars

The adoption of fiber-reinforced polymer (FRP) bars in lieu of traditional steel reinforcement for concrete structures has gained prominence. Nevertheless, prevailing international standards have not incorporated provisions to assess the significant contribution of FRP materials to the axial capacity and deformability of compression members. This study investigates the impact of Basalt (BFRP) ties on the axial performance of full-scale concrete columns reinforced with BFRP and Glass (GFRP) rebars, alongside traditional steel longitudinal rebars. Ten columns were subjected to concentric loading, with parameters including the type of longitudinal rebars (BFRP, GFRP, and steel), spacing of BFRP ties (180 mm, 120 mm, and 60 mm), and diameter of steel rebars (16 mm and 20 mm). Varied steel rebar diameters aimed to discern the influence of axial stiffness on column behavior. Results indicate an 18 % to 26 % higher axial load capacity in steel-reinforced concrete (RC) columns compared to FRP-RC columns. Both types of FRP rebars contributed approximately 12 % to the axial capacity. Reducing BFRP tie spacing from 180 mm to 60 mm significantly increased deformability by up to 250 % in FRP-RC columns and ductility by up to 14 % in steel-RC columns. The study highlights conservative predictions in existing design equations (ACI 440.11–22 and CSA S806-12) for the axial load capacity of BFRP and GFRP RC columns, underestimating by 14 % to 20 %, as they neglect the contribution of FRP rebars. Utilizing a concrete crushing strain of 3,000 µε and 3,500 µε as the ultimate FRP compressive strain produced predictions closest to the experimental axial load capacity.

Effect of macro-synthetic and hybrid fibres on the behaviour of square concrete columns reinforced with GFRP rebars under eccentric compression

GFRP rebars have emerged as a suitable alternative for steel rebars to tackle corrosion-related issues. However, the abrupt failure of GFRP-reinforced concrete (RC) elements due to the brittle behaviour of GFRP rebars is a significant concern. Fibre reinforced concrete (FRC) reduces brittleness by providing pseudo-ductility to GFRP RC members failing in compression. Moreover, fibre addition helps reduce crack widths by bridging them when subjected to tensile stresses. The current study aims to understand the influence of adding macro-synthetic Polyolefin (PO) and a hybrid mix of steel and PO fibres (HB) on the behaviour of GFRP-RC columns. Twenty-six square columns reinforced with GFRP rebars and discrete fibres are tested. A low-eccentricity to-width ratio (e/d of 0.2) and a high-eccentricity to-width ratio (e/d of 0.4) are chosen as loading parameters. The test matrix includes the following specimens: i) control with no fibres, ii) only PO fibres, and iii) a hybrid mix of steel and PO fibres. Test results show that specimens reinforced with hybrid fibres outperformed macro-synthetic fibres in energy absorption and strength improvement. They also had better post-peak behaviour under eccentric compression. Fibre addition increased the load resistance contribution of GFRP rebars and prevented the complete spalling of concrete cover. It also improved the deformabilty factors when compared to control columns with no fibres under eccentric compression.

Structural Behavior of GFRP - RC Slender Columns Under Various Eccentricity Loading Conditions

Abstract Glass fibers reinforced polymer (GFRP) were used to longitudinally and transversally 12 columns and while the other 4 columns were reinforced with steel or steel and GFRP as reference specimens. This research dealt with several parameters under different loading conditions, such as the reinforcing material and spacing between ties. This study aims to find out the ability of the reinforced columns with GFRP to bear the loads. In addition, investigate the mode of failure in these columns and their appropriateness in the structures since the columns are compression members. The tested results revealed that the concentric loading columns give higher resistance than their eccentrically loaded counterparts. Also, the hybrid column (steel and GFRP) had the highest peak load compared with the fully reinforced steel and GFRP columns. In addition, the fully GFRP RC- column had an ultimate load slightly less than its steel counterpart under the same loading condition.

Experimental and Numerical Investigation on the Behavior of Eccentrically Loaded Hybrid Steel and GFRP RC Columns

Experimental and Numerical Investigation on the Behavior of Eccentrically Loaded Hybrid Steel and GFRP RC Columns

Research on vibration control for glass fiber reinforced polymer reinforced concrete (GFRP RC) frames subject to seismic loading

Deterioration of concrete structures caused by corrosion of steel reinforcement is a significant problem worldwide with high remediation costs. This problem has been addressed by corrosion protection systems, which prevent chlorides from penetrating the concrete cover and reacting with steel reinforcement. However, these solutions are complex and require high maintenance costs. In this paper, we propose to add viscous dampers to GFRP RC frames to improve its energy absorption capacity under seismic loading. Three RC frames were designed; two GFRP frames, and one steel RC frame. The fundamental dynamic parameters of RC frames with and without viscous dampers were calculated and compared. Results show that GFRP and steel RC frames can reach a similar lateral deformation, but the former is more fragile, with failure occurring at the compression zone of beams. Our results show that the addition of viscous dampers reduces the lateral deformation and story drifts in the GFRP RC frames. Moreover, the energy dissipation of viscous dampers is more efficient at GFRP RC frames. We conclude that the ductility and energy dissipation capacity of GFRP RC frames can be improved by adding viscous dampers and high lateral confinement, which demonstrates better performance than steel RC frames.

A Numerical Study on the Performance of GFRP RC Beams Exposed to High Temperature

This paper presents and validates a numerical model utilizing the nonlinear finite element software ABAQUS/Standard to simulate the performance and failure of GFRP reinforced concrete beams under high temperature. A numerical model was firstly developed by selecting the proper geometrical and material modelling parameters with suitable analysis procedure available in ABAQUS/Standard. The developed numerical model was verified by comparing numerical results with the corresponding results of experimental test extracted from current study on GFRP-RC beams under different elevated temperatures ranges from (20 to 600ºC). Validation results have indicated the accuracy of the suggested numerical model. The validated numerical model was implemented to investigate the effect of important parameters on the performance and maximum load of GFRP-RC beams under different elevated temperatures that are not considered in the current experimental tests. These parameters include effect of exposed time or time- temperature history; effect of temperature distribution around the beams cross-section. Results indicate that the finite element software ABAQUS/Standard can reasonably predict the performance and ultimate load of GFRP-RC beams under different elevated temperatures.

The effects of bond, shrinkage and creep on cracking resistance of steel and GFRP RC members

The analytical and numerical models for combining the effects of bond, shrinkage, creep and ageing of concrete on the stress-strain state and cracking resistance of reinforced or prestressed concrete elements in a period prior to loading are proposed.A geometrical meaning of the coefficient of ageing is defined in terms of an average stress-strain approach. It is mathematically proven that this coefficient integrally establishes a continuous shape function of the actual concrete stress (or its increment) in a given period of time. This allows for substituting the rectangular stress diagram for the actual function of stress in time to attain the same areas of these diagrams and explicit predicting the stress-strain state in time by using algebraic equations for the inverse of Volterra integrals.The analytical formulae for predicting the cracking moment of the cross-section accounting for bond, shrinkage, creep and ageing of concrete are also proposed. It is demonstrated that the intense development of the partially recoverable instantaneous and creep strains play the main role. The proposed formulae are applicable to the assessment or retrofitting of the existing structures, where the full contact interaction techniques are inappropriate.

An effective stiffness model for GFRP RC cracked flexural members

Abstract There is no complete consensus of researchers on the problem of evaluating tension stiffening phenomena in cracked flexural glass fibre-reinforced polymer reinforced concrete members and, therefore, various empirical correction factors are used in the existing weighted averaging techniques for obtaining consistent estimates of experimental deflection of traditional steel bars reinforced concrete cross-sections. This paper presents an alternative method for deformational analysis of cracked GFRP RC flexural members based on constitutive modeling, taking into account the direct or inverse approach to evaluating the post-cracking stress-strain response of concrete in tension. The effect of tension stiffening is defined analytically by the derived formula for the effective moment of inertia, omitting the empirical correction of the moments of inertia of the uncracked or fully cracked RC cross-sections. Analytical formulae are also proposed to derive the parameters of tension stiffening based on the test data of GFRP RC beams subjected to bending. The relative systematic and random errors of the method are considered in the statistical analysis, involving the experimental sample of deflections for 42 beams. The case studies of manual calculation of the mid-span deflection of the beams by using the proposed technique and the inverse analysis for deriving tension stiffening parameters based on of the experimental data are also provided.

Flexural Behavior of GFRP RC Beam Strengthened with Carbon Fiber Reinforced Polymer (CFRP) Plate: Cracking Behavior

There has been much research conducted on the current performance of Fiber Reinforced Polymer (FRP) as reinforcement. It was due to FRP easier to maintain than steel during construction because of less weight. Laboratory works on the flexural behavior of concrete beams that with GFRP and CFRP use as a plate strengthening for the beam size 2800 x 200 x 250 millimeter. study of the pattern of cracking and failure modes of the beam will be compared between the ten types of beams consisting of steel reinforced beams , beam-reinforced GFRP and GFRP reinforced beams strengthened with CFRP with different lengths. Comparing between the beam bending performance was examined through the ultimate load, cracking and failure modes.

Material Factor for GFRP RC Structures in Canada

Degradation mechanisms of GFRP bar in real concrete are still not clear to civil engineers due to limited field applications. To avoid unsafe design, in current design codes a material factor is used to assure long-term safety of GFRP RC structures. This paper presents an assessment of material factors for GFRP bar as specified in Canadian Design Codes by predicting GFRP long-term performance with monthly average temperatures from 14 weather reporting stations in Canada. Results showed that the material factor varies from 0.57 to 0.61 for an application with 100% RH exposure, while a factor of 0.75 could be adequate for cases with exposure RH ≤90%. Considering the annual relative humidity across Canada, conclusion could be made that current factors in Canadian codes could provide sufficient safety margin.

Sustained Load Effect on GFRP Bar Reinforced Concrete Deck

This paper presents the investigation of sustained stress level in GFRP bar used as main reinforcement in typical reinforced concrete bridge deck, which is often subject to severe environmental exposures in North America. AASHTO LFRD approach is used for the design of GFRP RC deck that also meets with the requirements per as specified in ACI 440.1R-06. Research results show that the sustained stress level in GFRP bar varies in the range of approx. 3% -7% for bridge deck with various deck thickness and girder spacing.

Discussion of “Experimental Response and Code Models of GFRP RC Beams in Bending,” by M. Pecce, G. Manfredi, and E. Cosenza

A discussion of a paper with the aforementioned title by M. Pecce, G. Manfredi and E. Cosenza, published in this journal (Volume 4, Number 4, November 2000), is presented. The original paper concerned the behavior of glass fiber reinforced polymer reinforced concrete beams and slabs. The discusser makes comments and seeks clarification on several points, including reported cracking moments and tensile strength.

Closure to “Experimental Response and Code Models of GFRP RC Beams in Bending” by M. Pecce, G. Manfredi, and E. Cosenza

A closure to a discussion regarding a paper with the aforementioned title and authors is presented. The original paper was published in this journal (Volume 4, Number 4, November 2000, pp 182-190) and the discussion was published in this journal (Volume 6, Number 1, February 2002, p 70). The authors respond to discusser A. Kilpatrick's comments and requests for clarification on their paper, which concerned the behavior of glass fiber reinforced polymer reinforced concrete beams and slabs.