Glass Fiber Reinforced Polymer Strips Research Articles

STUDY THE EFFECT OF EXTERNAL CRACK ON THE MECHANICAL PROPERTIES OF COMPOSITE MATERIALS

Increasing the strength of the matrix material rather than increasing stiffness is frequently the primary objective when designing composite materials. This is typically the case when the matrix is made of brittle, low-strength material. the resilience of this matrix substance Usually, it is determined by the initial flaws in the raw material. Depending on the microstructure of the composite material, these flaws or fissures may be large or minor. The orientations of the foil fibers, which can be customized to improve the performance of the laminate, have a significant impact on the properties of fiber reinforced polymer (FRP) laminates. This study's goal is to look at how matrix cracking affects the mechanical characteristics of FRP chips. The presence and absence of exterior cracks are examined in unidirectional glass fiber reinforced polymer strips. Samples were manually cast using plastic molds constructed in accordance with ASTM standards. It were able to comprehend the impact of external cracking on composite materials through the mechanical tests that were conducted since it causes the material to weaken. Consequently, it is seen as a location where tensions are concentrated.

An experimental study on structural performance of reinforced concrete beams strengthened for combined flexure and shear by using NSM-GFRP strips

Near surface mounted fiber reinforced polymer (NSM-FRP) technique is the latest & most effective techniques used in strengthening the existing structural components, which requires strengthening against increased service loads, faulty design, environmental effects, etc. In the past, many researches on NSM technique have been carried out by using different cross-sectional shapes & dimensions of FRP materials to strengthen for shear & flexure. In the present experimental study, the behaviour of R.C. beams strengthened for combined flexure & shear studied. The beams of 150x150x700 mm size with M30 grade of concrete & Fe500 steel were considered. The control beams (unstrengthened) & strengthened beams using GFRP (Glass fibre reinforced polymer) strips were subjected to three point loading to study the behaviour of beams in combined shear & flexure. The main objectives were to assess the behaviour of strengthened beams with control beams & to study the influence of the orientation of shear strips. The beams were studied for the failure characteristics, yield & ultimate load carrying capacity, stress-strain behaviour, deflection, & crack patterns. From the test results, it’s been observed that, the load carrying capacity of the strengthened beams were increased, the improved in deflection, when compared to the control beams. The ultimate load carrying capacity of beams with shear strip orientation of 45°, 60° & 90° were increased by 50.3%, 39.3% & 25% respectively, compared to the control beams. This NSM strengthening technique can be advantageous & suitably adopted to enhance the load carrying capacity of the beams.

Experimental study and finite element modelling of the torsional behavior of self-compacting reinforced concrete (SCRC) beams strengthened by GFRP

The present study experimentally and numerically investigates the behavior of ten self-compacting reinforced concrete (SCRC) beams strengthened by various means of externally bonded glass fiber reinforced polymer (GFRP) strips and subjected to pure torsion. The experimental matrix is designed to explore the impact of the number of GFRP layers, the width of the strengthening layers, and the spacing between those layers on the ultimate torsional capacity, the ultimate angle of twist, ductility, and failure patterns with respect to an un-strengthened specimen. Tests revealed that the specimen that was strengthened along its whole length using three layers of GFRP sheets yielded the highest gain in the ultimate torsional moment of 33.3% compared to the un-strengthened specimen. Additionally, the highest gain in the energy dissipation capacity among all strengthened beams (209.4% higher than the control beam) was obtained when four layers of GFRP sheets spaced every 300 mm were installed. Moreover, a three-dimensional (3D) non-linear finite element analysis is carried out via ABAQUS software to predict the torsional characteristics of SCRC beams either strengthened by GFRP strips or kept bare. The numerical model well captured the failure patterns, torque versus angle of twist responses, stress distribution, and the ultimate load of SCRC beams strengthened by GFRP strips with respect to the experimental findings.

Cyclic Out-of-Plane Testing of Clay Brick Masonry Walls Strengthened with Glass Fiber-Reinforced Polymer Strips

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Compressive behavior of GFRP partially strengthened corroded RC columns subjected to freeze-thaw erosion

The compression test of glass fiber-reinforced polymer (GFRP) partially strengthened corroded reinforced concrete (RC) columns subjected to freeze-thaw cycling was conducted in this study. A total of 45 small-scale RC columns were prepared. The columns were firstly subjected to accelerated corrosion conditioning to obtain the target level of steel loss, and then partially strengthened with 2-ply GFRP strips; finally, the strengthened RC columns were subjected to different freeze-thaw cycles. The main parameters in this experiment were reinforcement corrosion degree (0, 10%, and 20%) and number of freeze-thaw cycles (0, 25, 50, and 75). The compressive behaviors of columns were evaluated in terms of failure mode, load capacity, load-displacement response, stiffness, and ductility. Results showed that GFRP partially strengthening could significantly improve the load capacity, stiffness, and ductility of corrosion-damaged RC columns, while the ultimate load capacity and stiffness of strengthened columns decreased with the increase of freeze-thaw cycles. Moreover, a design-oriented calculation method for the ultimate load capacity of GFRP partially strengthened corroded RC columns subjected to freeze-thaw cycles was proposed and validated by the experimental results.

An experimental research on reinforced concrete deep beams fully wrapped with fiber reinforced polymers against shear

This paper presents a comprehensive experimental study to investigate the shear behavior of reinforced concrete (RC) deep beams fully wrapped with fiber reinforced polymer (FRP) strips. A total of eighteen deep beams were tested and the test results were evaluated. The test parameters were the shear span-to-effective depth ratio, the number of FRP layers, the clear spacing of FRP strips and the type of FRP. According to the experimental results, as the shear span-to-effective depth ratio increased, the rate of increase in the shear capacity decreased. On the other hand, the rate of increase in the deflection capacity increased with the shear span-to-effective depth ratio. It was observed that the steel plates used at the supports and loading point affected the contribution of FRP strips and the shear behavior of beams. Moreover, increasing the number of FRP layers, reducing the clear spacing of FRP strips or using glass FRP strips enhanced the shear and deflection capacities of beams. A comparative study was also conducted based on the experimental results. Comparisons between the experimental results of this study and the predictions obtained from a total of twelve models consisting of those given by the codes and those proposed by various researchers. The model superior to the others statistically is the one proposed by the German code.

Experimental and numerical analysis of a novel curved sandwich panel with pultruded GFRP strip core

Curved sandwich structure made of glass fiber-reinforced polymer (GFRP) composite is emerging in the construction of non-linear architectures and wind turbine blades. In this work, a novel curved sandwich panel with pultruded GFRP strip core was proposed and studied. Compared with the common core materials such as foam and wood, pultruded GFRP strips can provide a higher stiffness and strength, particularly when used in large-scale sandwich structures. The proposed sandwich panel was manufactured through vacuum-assisted resin transfer molding process. A series of three-point bending tests was conducted to study the flexural behavior. The effect of surface thickness on the load-carrying capacity and failure mode was addressed. Then, a finite element analysis was conducted via ABAQUS and validated by the experimental results. The parametric study was performed to address the key design parameters. Both experimental and numerical results indicated that with the increased surface thickness, the failure mode could transition from the damage of glue seam to the transverse cracking inside the pultruded GFRP strip. Moreover, the load-carrying capacity can be improved with the thickened face sheet. In the end, this work successfully demonstrated the use of multilayer shell elements in the finite element modelling of the cracking behavior of glue seams.

An experimental study on flexural performance of RC beams strengthened by NSM technique using GFRP strips for a resilient infrastructure system

Near surface mounted method (NSM) is an emerging technique with wider scope in repair and rehabilitation. In this method as lesser repair material is used and as FRP is placed inside grooves it offers higher serviceability, resistance to corrosion, higher impact damage resistance and fire resistance there by providing higher long-term economy. This method of strengthening avoids adverse environmental impacts, interruptions to service therefore considerable savings in time and cost. Hence, NSM technique helps in building resilience into infrastructure system. This paper is to present the experimental work on enhancing flexural performance of reinforced concrete beams by implementing NSM method. The side near-surface mounted (S-NSM) is an alternative method used for applying fibre reinforced polymer (FRP) flexural strengthening on reinforced concrete (RC) beams as in practical case the bottom face of the beam may be some times inaccessible. The S-NSM method places the FRP grooves at the sides of the beam on either side, rather than at the bottom in the normal near surface mounted (NSM) method. The present study is carried out on the use of NSM for strengthening of RC deficient beam designed for 30kN with NSM composite material namely glass fibre reinforced polymer (GFRP) strips as reinforcement. The experimental work included control specimen and strengthened beams at different locations and orientations of GFRP that is both bottom NSM and side NSM method (both horizontal and vertical orientation of strips) are studied and these beams are subjected to two point bending flexural test. The effect of groove location, crack pattern, deflection at midspan and quarter span and also different modes of failure are the characteristics studied based on results obtained.

Axial Compressive Performance of a Composite Concrete-Filled GFRP Tube Square Column

A composite concrete-filled glass fiber reinforced polymer (GFRP) tube square column is a new type of composite column, where GFRP is externally wrapped over several GFRP square tubes to form a multicavity GFRP tube, and then concrete is poured inside. External GFRP wrapping methods can be divided into two types: entirely wrapped and strip-type wrapped methods. The former is superior to the latter in terms of performance under stress. However, difficulties are introduced in the construction process of the former, and substantial materials are required to wrap the entire structure. To examine the axial compressive performance for this new type of composite column and the impact of the wrapping method, we designed and fabricated one type of entirely wrapped composite column and two types of strip-type wrapped composite columns with clear spacings of 85 mm and 40 mm, respectively, and performed static axial compression tests. Through tests and numerical simulations, we obtained the failure mode, load–displacement curve, and load–strain curve of the specimen, and analyzed the impact of the externally wrapped GFRP on the mechanical behavior of the composite column. The results show that the composite column reached the peak load before the fracture of the GFRP tube fiber occurred, and the bearing capacity declined sharply to approximately 75% of the peak load after the fiber fractured, then entered a platform section, thereby displaying ductile failure. As the wrapped layers of GFRP strips increased, the load capacity of the specimen exhibited a linear growth tendency. Compared with the performance of the entirely wrapped method, the load capacity of the specimens in the W5040 group declined 9.8% on average, and the peak efficiency of the GFRP strips increased by 50%, thereby indicating that the use of appropriate GFRP layers and strip distance intervals can ensure the appropriate bearing capacity of composite columns and full utilization of GFRP material properties.

Behavior of Reinforced Concrete Beams Strengthened By GFRP Composites Subjected to Combined Bending and Torsion – Experimental Study

This paper presents an experimental investigation on the behavior of reinforced concrete beams subjected to combined bending and torsion, strengthened by using externally bonded glass fiber reinforced polymer (GFRP). The experimental work includes an investigation of three RC beams tested under combined bending and torsion. One beam is kept without strengthening as a control specimen, while the other two beams are strengthened using GFRP wrapping with different configurations. All RC beams have the same concrete grade and steel reinforcement. The strengthened beams in the experimental study include full wrapping with continuous GFRP sheets and discrete GFRP strips with the same GFRP reinforcement ratio. The load-mid span deflection curves and the torsional moment-twist angle curves were recorded to failure. The crack patterns and failure modes of the RC beams were also indicated. The Experimental results reveal that strengthening by using GFRP wrapping helped effectively in improving the overall performance of the strengthened beams.

A Review on experimental and numerical studies of Glass Fibre Reinforced Polymer (GFRP) strips strengthened Reinforced Concrete (RC) slab subjected to low velocity impact

This paper reviewed the previous research on experimental and numerical studies on the impact behaviour of fibre reinforced polymer (FRP) strips reinforced concrete (RC) slab with various (FRP) strips arrangement. This review focusses on the effect of thicknesses, arrangements of FRP strips and type of support layouts. Initially, a throughout investigation was made on the FRP and its properties. Experiments associated to impact resistance of RC slabs was also performed. Furthermore, numerous finite element model (FEM) of RC slabs externally strengthened with different arrangement FRP strips were developed with ABAQUS and ANSYS. The numerical simulations on impact resistance of RC slab models externally strengthened with different arrangement FRP strips were performed. Generally, the experimental results displayed the diagonal two-way arrangement FRP strips externally bonded on bottom surface of RC slabs and four hinge supports applied had improved the impact strength significantly. The experimental and numerical impact results obtained for RC slabs externally strengthened with FRP strips were better as compared to the control RC slabs without FRP strengthening. Afterwards, the results gained from numerical was validated with experimental results. Finally, the methods and results of experimental and numerical reviewed was reliable as a reference for the study of RC slab externally strengthened with GFRP strips subjected to low velocity impact.

Strength Capacity Cracks Propagations Deflection and Tensile Enhancement of Reinforced Concrete Beams Warped by Glass Fiber Reinforced Polymer Strips

Different approaches were adapted to strength the structural elements to increase the load capacity and reduce the deformation such as deflection. The easiest and light external strengthening of reinforced concrete members are Fiber Reinforced Polymer (FRP) family such as Armed, Carbon, Glass and Basalt, respectively. This paper presents the theoretical approach to check out the experimental tests of reinforced concrete beams strengthened by glass fiber reinforced polymer (GFRP) using finite elements method by ANSYS software in which all models are simulate the tested beams. All models have the same geometry and mechanical properties but differ in GFRP layers and width. The main objectives of present work are evaluating the strength capacity, cracks propagations, deflection and tensile enhancement of reinforced concrete beams warped by GFRP strips subject to four points static load. Analysisof results indicate that the presences of GFRP sheets enhance the capacity and ductility of reinforced concrete beams in additional to delay the post crack concrete. The delay in the formation of first crack, increase in the number of cracks and ultimate loads of the models compared with the control model. There are improvements in flexural strength based on the modulus of rupture. Also, the cracks propogation become less in case of presence of GFRP and there is improvements in tensile resistance due to flexural. Analysis results inicated that the presence of GFRP at the bottom face of reinforced concrete beam in case of two layers gave increase in ultimate load 104.3% as compared with the control model. The reduction of the deflection for same models is 10.84%. Factor of the modulus of rupture range between (0.76-1.36) that is more than with ACI code suggested as 0.6. All model results were close to the experimental tests.

Performance of axially loaded reinforced concrete rectangular columns strengthened with GFRP strips

Abstract Sticking of glass fibre cloth around a column using epoxy resin is one of the solutions for column strengthening. This paper details a study on short reinforced concrete (RC) rectangular columns having rounded edges with axial load strengthened using bi-directional Glass Fiber Reinforced Polymer (GFRP) cloth glued with epoxy resin. The results obtained, indicate a notable increase in axial load capacity of RC rectangular column when wrapped with GFRP fabric around the column and stick with epoxy resin as glue. Wrapping completely around the column with strips is better than wrapping with single continuous fabric. Considering the width of strip, strips having more width are giving finer results than narrow width strips. When strips of two or more layers are wrapped, then staggering of strips is even better than sticking one strip merely on another. The axial load capacity is increased by the use of two layers of GFRP strips and sticking three layers of GFRP strips showed a decrease in the axial load capacity.

Experimental Study on GFRP Strips Strengthened New Two Stage Concrete Slabs under Falling Mass Collisions

In the course of global terrorist events prominent risks were faced by military and civilian infrastructure. Subsequently, the design of structures to resist impact load has become vital in the design process. Fibre reinforced polymer sheets were utilized as exceptional material to enhance the resistance of the structure to impact load. Until now, most researchers focused on the response of Fibre Reinforced Polymer (FRP) strengthened slabs under static load. Extensive research on the impact response of FRP strips strengthened slabs is relatively rare and the outcome of these investigations have been controversial. Therefore, it is vital to comprehend the response of FRP strengthened slabs subjected to falling mass collisions. In this study, impact response of Glass Fibre Reinforced Polymer (GFRP) strips strengthened Two Stage Reinforced Concrete Slabs (TSRCS) have been examined through experiments. Two different widths of 50 mm and 75 mm GFRP strips were used in perpendicular and oblique ways in one and two directions while strengthening TSRCS. In Total, a nine 1,000 mm × 1,000 mm × 60 mm TSRCS were fabricated and later impacted by a steel cylinder of 55 kg dropping at the centre from a 3,000 mm height. Study parameters analysed to discover the impact response of TSRCS include, impact-force history, acceleration, damaged area (top and bottom face), damage area ratio, damage volume ratio, and damage pattern. The results revealed that the slab strengthened with 75 mm GFRP strips was more effective in alleviating damage volume ratio compared to the 50 mm GFRP strips. Also, the obtained results in this study shed light on the impact performance of two stage reinforced concrete slabs.

RC beam models damaged and strengthened with GFRP strips under bending loading and free vibration

Four reinforced concrete (RC) beam models undamaged, damaged by notches and strengthened by external bonded (EB) glass fiber reinforced polymer (GFRP) strips have been experimentally studied. The paper aims to assess the availability of strengthening with EB GFRP strips in RC beams having a deep localized damage. The behavior of RC beams has been analysed under bending loading until failure. Furthermore, the assessment of RC beam models foresaw nondestructive control of damaged and strengthened models by free vibration tests to obtain frequency values at different damage degree. Damage, artificially obtained by notches with different width, on the midspan section and on the lateral location of beams, has been analysed. The envelope of frequency response functions (FRFs) obtained by dynamic tests was elaborated and changes of natural frequency values are then correlated to damage both to non-strengthened beam with notches and to strengthened beam models. Results of static tests on RC beams strengthened with filled mortar in the notched sections and EB GFRP strips have allowed to validate the strengthening of RC elements with composite material characterized by relatively low elastic modulus; further, it has been assessed maintenance of bond between concrete surface and GFRP strips until failure under bending loading.

Dynamic performance enhancement of RC slabs by steel fibers vs. externally bonded GFRP sheets under impact loading

Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined.Performance of fourteen 1000 × 1000 × 75 mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs containing steel fibers with different volume fractions and nine steel RC slabs strengthened with externally bonded GFRP sheets or strips under impact loads induced by drop weight is experimentally examined. In this article, crack development, failure modes and dynamic responses including displacement-time, strain-time, as well as acceleration-time are investigated and compared between slabs with various configuration. In addition, finite element analyses are carried out using LS-DYNA explicit software. The results indicate that increasing the bottom layer GFRP enhances the performance of RC slabs under impact loads. In general, slabs with totally bottom GFRP layers provide better performance than those with steel fibers.

The influence of interaction between NSM and internal reinforcements on the structural behavior of upgrading RC beams

In this paper, the effect of interaction between near surface mounted (NSM) strips and internal reinforcement on the structural behavior of upgrading RC beams has been studied. The position, arrangement and area of NSM glass fiber reinforced polymer (GFRP) strips have been examined experimentally. Six strengthened beams in addition to one control beam were tested in flexural until failure. The load carrying capacity, deflections and the mode of failure of strengthened beams were recorded. The experimental results showed that the installed NSM GFRP side by side has a lower interfacial stress than those installed separated. This improvement is more obvious in the case of NSM strips installed near the internal reinforcement. Furthermore, the installed NSM strips in deep groove experienced higher load carrying capacity than those installed in shallow groove for both patterns. The installation of the NSM GFRP strips in deep grooves using epoxy may be delay or prevent the peeling/debonding failure. The ultimate load of the beam upgraded with one NSM strip adjacent to the stirrups (in deeper groove) is about 1.5 times that of one NSM strip installed near the bottom surface of the beam. This ratio decreased with increasing the area of NSM GFRP strips.

Strengthening and Retrofitting Precast Concrete Buildings to Mitigate Progressive Collapse Using Externally Bonded GFRP Strips

Compared to cast-in-situ RC buildings, precast concrete (PC) buildings may have lower redundancy and integrity depending on their construction methods and the types of beam-to-column connection. In this study, a series of multipanel PC beam-column-slab substructures were tested to evaluate the performance of a typical existing PC building with bolted connection, which is a typical dry connection in industrial buildings, subjected to the loss of a single penultimate column scenario. It was found that an existing PC substructure with bolted connections exhibited very low ductility and load-resisting capacity. The deficient connection between the PC slab and beams led to the specimen failing in a brittle manner and gaining fewer benefits from tensile membrane action. To overcome the poor performance of existing PC buildings with bolted connections, improvement in detailing and strengthening schemes relied on glass fiber–reinforced polymer (GFRP) strips were proposed. Based on the test results, the improvement could enhance the redundancy of PC substructures effectively. Moreover, the proposed strengthening scheme further enhances the flexural capacity, initial stiffness, and the postpeak behavior in large deformation stage significantly.

Mechanical prestressing of annealed glass beams using pretensioned GFRP: Characterisation and potentiality

This paper presents the results of an experimental investigation on the mechanical behaviour of annealed glass beams prestressed using adhesively-bonded pretensioned Glass Fibre Reinforced Polymer (GFRP) strips. The results show that the glass beams prestressed using pretensioned GFRP showed an increased load capacity compared to equivalent glass beams reinforced with unprestressed GFRPs. The prestressed glass beams showed a notable ductile post-cracked behaviour similar to annealed glass beams reinforced with unprestressed GFRP strips. The results also show that the proposed glass prestressing technique prevented premature debonding of the GFRP strips from the glass beams and explosive final failure of the glass beams, unlike in the mechanically-prestressed glass beams investigated in the literature where these failures were commonly observed.

Strengthening of Axially Loaded Reinforced Concrete Rectangular Columns with GFRP Strips

Abstract The present study focuses on studying the load carrying capacity of short reinforced concrete rectangular axially loaded columns with rounded edges strengthened using Glass Fiber Reinforced Polymer (GFRP) bi-directional fabric strips glued with epoxy resin. Columns are wrapped with GFRP in the form of strips of different sizes. The area/material of GFRP wrapped in all patterns for each aspect ratio is the same. The number of FRP layers is varied. Different column sizes with the same cross sectional area and length are considered with aspect ratios 0.5, 0.6, 0.72, 0.84 and 1. Experimental results indicate a significant increase in load carrying capacity of RC rectangular column when strengthened by wrapping GFRP fabric with epoxy resin as glue. Wrapping with 83.3mm strips gave good results than 50mm strips. As number of layers increases load carrying capacity increases up to two layers only, sticking of three layers showed decrease in load carrying capacity. The GFRP strengthening is more effective when the aspect ratio is less.