Carbon Fiber Reinforced Polymer Strips Research Articles

Simulation of Two-way Slabs Strengthened in Punching with CFRP Strips

Two-way slabs are vulnerable to two-way punching shear which may cause catastrophic failures. Furthermore, over the recent past, the trend has been set to use construction waste as recycled aggregates in structural concrete. Therefore, the work presented herein, numerically investigates in detail, the response of the natural aggregate concrete (NAC) and recycled aggregate concrete (RAC), two-way reinforced concrete (RC) slabs both under punching shear. The work also focuses on simulating the behavior of such slabs strengthened and/or retrofitted with the strips of carbon fiber reinforced polymer (CFRP). The detailed numerical investigation revealed that the overall stiffness of slabs strengthened with CFRP increased when compared with NAC and RAC slabs having no CFRP. The placement of the strips from the face of the column was also found to be effective in reducing the deflections of the slabs at similar load levels. For both NAC and RAC specimens, the influence of slab thickness and concrete compressive strength was found to be influencing parameters on the behavior of the slabs.

Geopolymer adhesive for sustainable NSM CFRP strengthening of RC structures

Carbon fiber reinforced polymer (CFRP) composites are known to be a very effective materials for strengthening and rehabilitation of reinforced concrete (RC) structures. Near surface mounted (NSM) technique, has been used as an effective method for this purpose, over the past two decades. The conventional technique benefits from the superb properties of polymeric adhesives like epoxy resins, to ensure a successful transfer of stresses between the CFRP and concrete substrate. However, the vulnerability of polymeric matrices to high temperatures motivated researchers to focus on developing cement-based adhesives for NSM CFRP systems for special applications where fire safety is an issue. Recently, efforts led to promising outcomes for the future of these novel systems. This upgrade not only fulfills the fire safety measures but also is necessary from the environmental point of view, due to the pollution and health problems associated with the usage of epoxy resins as conventional adhesives for FRP systems. While improvements occurred in the bond performance of the NSM CFRP systems with cement-based adhesives, using innovative sand-coated CFRP strips, the alternative sustainable approaches could be also investigated. This paper is dedicated to assessing the adoption of a geopolymer adhesive, to serve as a matrix for NSM strengthening techniques, using special sand-coated CFRP strips. Bond tests have been performed in ambient and thermo-mechanical conditions, and results showed promising performance of adoption of geopolymer in this technique. Also, a brief analysis of the environmental impact of using geopolymer as an alternative sustainable matrix is discussed, compared with epoxy resin and cement-based adhesive as its competitors, for eco-friendly strengthening systems for RC structures.

Strengthening of GFRP Reinforced Concrete Slabs with Openings

Using fiber-reinforced polymer (FRP) could effectively improve the strength and endurance of reinforced concrete (RC) constructions. This study evaluated the flexural behavior of one-way concrete slabs with openings reinforced with glass fiber-reinforced polymers (GFRP) bars. It strengthened using carbon fiber-reinforced polymer (CFRP) sheets around the openings. The experimental program of this study is adopted by casting and testing four one-way concrete slabs with dimensions of (150*750*2650) mm. These slabs are divided into two groups based on whether they were strengthened or un-strengthened. For each group, two different openings (either one rectangular or two square) measured 250*500 mm and 250*250 mm, respectively, were fabricated within the pure flexural zone of the specimens. The experimental results indicate that using CFRP strips increases the maximum load capacity by around 29% for the slab with one rectangular opening and 21% for the slab with two square openings compared to the un-strengthened slabs. On the other hand, the deflection at a service load is decreased by about 35% and 37% for the slabs mentioned above, respectively.

Strengthening of Reinforced Concrete Beams via CFRP Orientation

The utilization of externally bonded carbon fiber-reinforced polymers (CFRPs) and glass fiber-reinforced polymers (GFRPs) for reinforcing and retrofitting components has garnered considerable interest recently, as such composites provide beneficial properties, including a high modulus of elasticity, high strength, and low weight. This work conducts a finite element analysis, verified through laboratory experiments on 14 reinforced concrete (RC) beams. The primary focus is the final load of these components, considering varying CFRP orientations relative to the loading direction. In this research, the performances of control beams and RC beams are compared to assess the effectiveness and efficiency of different strengthening methods. The results demonstrated that bonding CFRP sheets with V-shaped end anchorages on the tension side was highly effective in improving the flexural capacity of RC beams in the weaker concrete strength group. This strengthening method resulted in a substantial increase in strength (of around 29.8%) in the higher concrete strength group. In addition, utilizing V-shaped end anchorages to bond CFRP sheets on the tension side proved to be a highly efficient technique for improving flexural strength. Conversely, bonding inclined CFRP strips to the sides of RC beams was highly effective at enhancing the shear capacity of the beams. These outcomes convincingly demonstrate the effectiveness of FRP for the reinforcement of structural components. The specimens strengthened with inclined strips exhibited enhanced shear and deformation capacity compared to those strengthened with vertical strips.

Flexural-shear strengthening of reinforced concrete T-beams subjected to asymmetric loading using CFRP system combined by NSM strips and U-wraps

This paper presents a developed three-dimensional (3D) finite element model (FEM) of flexural and shearstrengthening of reinforced concrete (RC) T-beams using a CFRP (Carbon Fiber-Reinforced Polymer) system combined by near-surface mounted (NSM) strips and U-wraps subjected by asymmetric loading. The 3D FEM was verified by experimental results. Concrete was simulated by a total-strain-based rotating smeared crack model. NSM CFRP strips and CFRP U-wrap sheets were modeled as shell elements. Steel reinforcement and NSM CFRP strips were embedded in concrete, corresponding to a perfect bond. U-wrap sheets were modeled as a shell element and bonded to the concrete surface using an interface element, considering appropriate bond properties. Four RC T-beams from an experimental work were analyzed, and predictions of the applied load-displacement curve and failure mode were presented to demonstrate the accuracy of the developed finiteelement analysis. It is shown that the finite element results of T-beams agree well with the experimental behavior in terms of applied load versus displacement and failure mode. Moreover, a parametric study was conducted to examine the influence of some design-oriented parameters such as concrete compressive strength, amount of longitudinal tension reinforcement, amount of stirrups, multiple layers of externally bonded (EXB) CFRP sheets, and flange width.

Axially-compressed behavior of carbon-FRP strengthening CFT short columns having circumferential void defects

To clarify the viability of externally bonding carbon-fiber-reinforced polymer (FRP) for strengthening the structural integrity of concrete-filled steel tube (CFT) short columns having circumferential void defects, this study comprehensively explores the strengthening effectiveness of various wrapping parameters (i.e., carbon-FRP strength, wrapping layers, and wrapping ratio) on the axially-compressed CFT short columns with various void ratios, material strengths, and geometric parameters by numerical method. Detailed mechanical responses, encompassing failure patterns, load-shortening (N-Δ) curves and stress distribution, are delved to reveal the strengthening mechanisms. Finally, strength prediction formulas for these composite columns are proposed rooted in the ring extension and local force transmission theories. Results show that the presence of initial voids delays the occurrence of steel-concrete contact stress (p) and weakens the p-value at peak load, thus reducing the axial resistance of column. Particularly when the void ratio exceeds 0.2%, the longitudinal strain when the concrete contacts with outer tube is beyond the concrete's peak compressive strain, thus the shape of the N-Δ curve is obviously changed, exhibiting two peaks. Externally bonding carbon-FRP strips can obviously improve the peak load of the column with a void ratio ≤ 0.2%. If the void ratio exceeds 0.2%, externally bonding carbon-FRP strips can also improve the column's second peak load, even exceeding the strength of pure CFT column, while it has no effect on the first load. The formulas proposed herein have a satisfactory accuracy based on the tested validation, which are expected to guide the design of strengthening scheme in engineering.

Shear capacity of PVC-CFRP confined concrete column-RC beam interior joint strengthened with core steel tube

This paper presents an experimental investigation on polyvinyl chloride (PVC)-carbon fiber reinforced polymer (CFRP) confined concrete (PCCC) column-RC beam interior joint strengthened with core steel tube (CST). Thirteen interior joints are designed and tested under low cyclic loading considering the impacts of six variables, such as diameter-thickness ratio of CST, stirrup ratio of joint, axial compression ratio, CFRP strips spacing, reinforcement ratio of beam and reinforcement ratio of column. Distinct shear deformation in joint region finally dominates the failure of specimens. The load-displacement hysteretic curves are relatively full and eventually show inverse S shape, indicating the specimens have considerable seismic behavior and energy dissipation capacity. The yield and peak shear capacities increase as diameter-thickness ratio, stirrup ratio of joint, reinforcement ratio of column or reinforcement ratio of beam increases. Comparatively, the axial compression ratio and CFRP strips spacing exert less influence on shear capacity. Considering the impact of diameter-thickness ratio, stirrup ratio of joint and reinforcement ratio of column, a formula for estimating shear capacity of PCCC column-RC beam interior joints strengthened with CST is proposed and its accuracy is verified by test data.

Rehabilitation of post‐heated rectangular reinforced concrete columns using different strengthening configuration

AbstractIt is common knowledge that increased temperatures have a negative impact on the axial load‐capacity and stiffness of reinforced concrete (RC) rectangular columns. This is something that is commonly acknowledged. For the purpose of restoring the axial capacity and stiffness of heat‐damaged RC columns, it is absolutely essential to carefully pick a suitable method for strengthening and repairing the columns. This research paper investigates the performance of various strengthening methods, such as the use of carbon fiber‐reinforced polymer (CFRP) jackets with near‐surface mounted (NSM) steel bars and a combination of welded wire mesh (WWM) and CFRP strengthening techniques, for the rehabilitation of RC rectangular columns that have been damaged due to exposure to high temperatures. Specifically, the paper focuses on the performance of these methods in relation to the rehabilitation of RC rectangular columns. There were three groups of tested RC rectangular columns: pre‐heated and unstrengthened, post‐heated and unstrengthened, and post‐heated and strengthened. Over a period of 3 h, 600°C was applied to the heated columns. Both a scheme utilizing a combination of unidirectional CFRP strips and NSM steel bars and another utilizing a combination of unidirectional CFRP strips and WWM were evaluated. Axial compression tests were performed on each column until failure occurred. The experimental test outcomes revealed that exposure to high elevated temperatures led to a decrease in the axial load‐carrying capacity of 38.6% and a decrease of 75.9% in initial stiffness, compared to unheated RC columns. Both strengthening schemes proved effective in restoring and surpassing the initial load‐carrying capacity of undamaged RC rectangular columns by an average of 35%. Notably, the combination of CFRP strips and WWM exhibited superior performance in restoring the initial stiffness of post‐heated RC rectangular columns, representing a novel finding. The strengthening scheme employing WWM and CFRP recovered 61.3% of the lost axial strength caused by high temperature, while the NSM/CFRP scheme restored 34.5% of the lost axial strength. In addition, the utilization of NSM in combination with CFRP strips as well as utilization of the WWM and CFRP systems leads to stiffness enhancement of 52.1% and 123.7%, respectively, when compared to post‐heated and unstrengthened RC columns. However, the study's findings have clearly shown that combination of WWM and CFRP strips is efficient in enhancing the strength of heated and unheated damage RC beams.

Full-Range fatigue behavior of NSM CFRP-to-Concrete bonded joints

The interfacial bond characteristics and failure mechanism of near-surface mounted (NSM) fiber reinforced polymer (FRP) composites in concrete under fatigue loading are less understood compared to their bond behavior under static loading. In this paper, degradation of the local bond strength of FRP-to-concrete bonded joints subjected to direct pull-out fatigue loading is presented for both carbon FRP (CFRP) rods and strips under different fatigue load ranges, i.e., 10–50%, 10–60%, and 10–70%, of the corresponding static load-carrying capacity. The interfacial debonding between FRP and adhesive was observed during fatigue cycles for CFRP rod specimens to different extents. Specimens using CFRP rods with sand-coated and spirally wound surface treatment presented a higher local bond strength and a slower degradation rate, as compared to the ones using CFRP rods with roughened or sand-coated treatment. Using epoxy adhesives with higher strengths benefitted the fatigue bond performance of the tested specimens in terms of local bond strength and stable behavior. Higher fatigue load ranges substantially accelerated the local bond degradation resulting in a much shorter fatigue life of the bonded joints.

Experimental and finite element analysis of reinforced concrete multi-cell box girders retrofitted with carbon fiber reinforced polymer strips under torsion

This study expands the state of the art in studies that assess torsional retrofit of reinforced concrete (RC) multi-cell box girders with carbon fiber reinforced polymer (CFRP) strips. The torsional behavior of non-damaged and pre-damaged RC multi-cell box girder specimens externally retrofitted by CFRP strips was investigated through a series of laboratory experiments. It was found that retrofitting the pre-damaged specimens with CFRP strips increased the ultimate torsional capacity by more than 50% as compared to the un-damaged specimens subjected to equivalent retrofitting. This indicated that the retrofit has been less effective for the girder specimen that did not develop distortion beforehand as a result of pre-loading. From experimental observations, when the girder specimen was cracked and the transverse steel reinforcement bars started straining, the CFRP strips started to work more effectively and contributed together with the transverse steel reinforcement to resist torsion load. Additionally, Finite Element (FE) simulations were developed using Abaqus to model the torsional behavior of the retrofitted girders, the results of which were validated with the experimental data. With the numerical model, the effect of concrete compressive strength, transverse reinforcement spacing, and CFRP strip spacing were examined. The effectiveness of the CFRP strips in enhancing the torsional strength of the girder was found to increase with increasing the spacing between the transverse reinforcement.

Fatigue performance improvement of U-rib butt-welded connections of steel bridge decks using externally bonded CFRP strips

U-rib butt-welded connections in steel bridge decks are known to be highly susceptible to fatigue cracking, which can pose a direct threat to the safety and durability of bridge structures. Carbon fiber-reinforced polymer (CFRP) materials have shown promising potential for fatigue strengthening. This study investigated the effectiveness of CFRP application on the fatigue performance of U-rib butt-welded connections by employing full-scale fatigue tests and finite element analysis. Two single U-rib specimens with welded splice joints were initially tested to initiate real fatigue cracks under cyclic loading. Different techniques of CFRP installation were then proposed to promote the fatigue performance of cracked butt-welded connections. The failure modes and fatigue strength of the tested specimens were evaluated before and after strengthening. Research results showed that fatigue cracks were observed at the arc transition of butt welds, where remarkable incomplete penetration was also discovered. The fatigue strength grade of the tested U-rib butt-welded details was less than 71 MPa stipulated by Eurocode 3. However, after being repaired by CFRP sheet bonding, the equivalent fatigue life of U-rib butt welds with different damage degrees can be extended by 0.5–16.6 times that of the original ones. These findings suggest that CFRP strengthening should be applied instantly on U-rib butt-welded connections once fatigue cracks are found.

CONFINED REINFORCED CONCRETE VERTICAL ELEMENT DUCTILITY UNDER LATERAL LOAD: INFERENCE FROM TEST RESULTS

Vertical elements fail during earthquakes due to lateral load. Carbon-fiber-reinforced polymer (CFRP) can play a significant role in preventing sudden collapse due to lateral load. Confinement provided by transverse shear reinforcement and polymer sheets increases both the compressive and lateral strength of concrete. To test the effect of CFRP confinement on concrete columns, seven square and four circular vertical specimens were tested and results were compared with theoretical predictions at Bangladesh University of Engineering and Technology. The specimens were wrapped at the vertical portion on an intermittent basis so that CFRP strips fell at the gap of horizontal reinforcements of the specimens’ vertical portion. Cyclic shear test was performed while maintaining axial compression. The test results were close to the theoretical predictions. The results thus suggest that CFRP wraps can contribute increased shear strength and ductility of vertical elements. High-strength concrete specimens did not reach their maximum strength due to the testing facility’s limitations, but they provided the expected results in the lower bound.

Experimental and Numerical Study on RC Beams Strengthened by NSM Using CFRP Reinforcements

Near Surface Mounted (NSM) Carbon Fiber-Reinforced Polymer (CFRP) reinforcement technique to improve the flexural strength of reinforced concrete members has become increasingly attractive in recent years. In this study, the practical problem of concrete cover depth cutting limitation was investigated. Twelve specimens were tested by four-point bending until failure. Experimental parameters include concrete cover depth, CFRP reinforcement type, CFRP positioning, and stirrups status. Furthermore, a nonlinear FEA model was developed to simulate the tested beams and was able to predict the experimental behavior satisfactorily. A series of parametric studies were then performed using this model to understand the effect of various reinforcement parameters on the flexural performance of the beam. The results showed that Strengthening with CFRP resulted in a significant increase in yield and ultimate strengths, but a significant ductility loss was recorded due to CFRP strip debonding in the strengthened beams, this problem was addressed by using more efficient strengthening techniques utilizing the effective bond length and a proper groove depth and positioning for the NSM bars.

Experimental Study of Pre-Cast Reinforced Concrete Deep Beams (Hallow Core section) Retrofitting with Carbon Fiber Reinforced Polymer (CFRP)

Experimental programs based test results has been used as a means to find out the response of individual elements of structure. In the present study involves investigated behavior of five reinforced concrete deep beams of dimension (length 1200 x height 300 x width150mm) under two points concentrated load with shear span to depth ratio of (1.52), four of these beams with hallow core andretrofit with carbon fiber reinforced polymer CFRP (with single or double or sides Strips). Two shapes of hallow are investigated (circle and square section) to evaluated the response of beams in case experimental behavior. Test on simply supported beam was performed in the laboratory & loaddeflection, strain of concrete data and crack pattern of those five reinforced concrete beams was recorded. Parametric studies are also conducted in this study includes the effect of hallow opening (shapes and materials), and CFRP ratio (single, double strips and side horizontal stirrups). Comparisons of test results from experimental data are based on load capacity, deflection, crack pattern and strain of concrete for all beams. From this comparison it was found that hallow effect on strength capacity i.e. decrease by about (13%) and increased in deflection and strain by about (18%, 24%) respectively compared with solid section. Also find that CFRP give more enhancements in loading capacity by about(33 to 66%) and decreased deflection for same applied load by about (26%). Test results that show when sides of beams retrofit with CFRP strip against horizontal shear increased strength by about by (20%). Finally the using double CFRP strips for hallow section gives equivalent or more than strength capacity of solid section.

Prediction of fatigue crack propagation in center cracked steel plate strengthened with partially covered CFRP strip

Evaluating the fatigue performance of steel members strengthened with carbon fiber reinforced polymer (CFRP) is of great significance for formulating maintenance strategies and making full use of materials. Current analytical models are mainly developed for fully covered CFRP strengthening method without considering different mechanisms at each stage. In this paper, an analytical model considering different stages of crack propagation was proposed to predict the fatigue performance of center cracked steel plates strengthened with partially covered CFRP strips. The strengthening effects of CFRP strips were numerically analyzed based on the extended finite element model (XFEM) calibrated by test data. The validity of the analytical model was checked by several sets of test data and numerical simulations. The results show that the proposed analysis model can reasonably predict the fatigue life of center cracked steel plates strengthened with partially covered CFRP strips. This study may provide a reference for the application of the partially covered CFRP fatigue strengthening method in engineering structures.

Enhancement of collapse-resistant capacity of non-seismically designed RC frames using various CFRP strengthening schemes

The existing studies have demonstrated relatively weak robustness of non-seismically designed reinforced concrete (RC) frames against collapse than seismically designed RC frames, causing the demand of efficient strengthening schemes to enhance their collapse-resistant capacity. Therefore, this paper presents an experimental program aiming at strengthening the collapse-resistant capacity of non-seismically designed RC frames using carbon fiber reinforced polymer (CFRP). A total of seven sub-frames were tested, of which the penultimate column or edge column was notionally removed to replicate the initial damage caused by accidental loads. Two sub-frames without strengthening were tested first as reference tests. Similar to existing research outcomes, the referential sub-frames experienced premature rebar fracture at the beam ends near the removed column, resulting in a severe softening in load resistance. Whilst the load resistance could reascend, the fracture of the rebar at the beam ends near the side columns only allowed an insufficient mobilization of catenary action (CA). In addition, the side joint of the referential sub-frame representing a penultimate column removal scenario suffered significant damage. Subsequently, five strengthening schemes were applied to the referential sub-frame, they are designed to increase the compressive arch action (CAA) capacity or CA capacity, or both the CAA and CA capacities through CFRP strengthening. Test results demonstrated that the proposed strengthening schemes in this paper can efficiently increase the load resistance at the CAA and CA stages but failed to mitigate the severe load resistance softening. The strengthening scheme planned to increase the CAA capacity unexpectedly decreased the deformation capacity of the strengthened sub-frame due to premature fracture of beam rebar near the side columns. The strengthening schemes planned to increase the CA capacity or both the CAA and CA capacities could increase not only the CAA capacity but also the CA capacity. The enhanced load resistance at the CA stage was mainly attributed to the continuous CFRP strips attached to the soffits. Unfortunately, the energy method demonstrated that the dynamic load resistance of the tested sub-frames to prevent collapse was achieved at the CAA stage rather than the CA stage because of the severe load resistance softening. Thus, the efforts devoted to increasing the CA capacity by this paper were valid in a real collapse of building scenario. In addition, 113 available test results were collected to compare with the acceptance criteria in existing codes for collapse-resistant design. Based on the test results and comparison, design suggestions were given for the collapse-resistant design.

Load-Bearing Performance of Non-Prismatic RC Beams Wrapped with Carbon FRP Composites

This study investigated the influence of CFRP composite wrapping techniques on the load–deflection and strain relationships of non-prismatic RC beams. A total of twelve non-prismatic beams with and without openings were tested in the present study. The length of the non-prismatic section was also varied to assess the effect on the behavior and load capacity of non-prismatic beams. The strengthening of beams was performed by using carbon fiber-reinforced polymer (CFRP) composites in the form of individual strips or full wraps. The linear variable differential transducers and strain gauges were installed at the steel bars to observe the load–deflection and strain responses of non-prismatic RC beams, respectively. The cracking behavior of unstrengthened beams was accompanied by excessive flexural and shear cracks. The influence of CFRP strips and full wraps was primarily observed in solid section beams without shear cracks, resulting in enhanced performance. In contrast, hollow section strengthened beams exhibited minor shear cracks alongside the primary flexural cracks within the constant moment region. The absence of shear cracks was reflected in the load–deflection curves of strengthened beams, which demonstrated a ductile behavior. The strengthened beams demonstrated 40% to 70% higher peak loads than control beams, whereas the ultimate deflection was increased up to 524.87% compared to that of the control beams. The improvement in the peak load was more prominent as the length of the non-prismatic section increased. A better improvement in ductility was achieved for the case of CFRP strips in the case of short non-prismatic lengths, whereas the efficiency of CFRP strips was reduced as the length of the non-prismatic section increased. Moreover, the load–strain capacity of CFRP-strengthened non-prismatic RC beams was higher than the control beams.

Nonlinear Analysis on Torsional Strengthening Of Rc Beams Using Cfrp Laminates

This research is devoted to investigate the behavior and performance of reinforced concrete beams strengthened with externally bonded Carbon Fiber Reinforced Polymer (CFRP) laminates under the effect of torsion. In this study a theoretical analysis has been conducted using finite element code ANSYS. Six previously tested beams are used to investigate reinforced concrete beams behaviorunder torsion, two of them are solid and the rest are box-section beams. Also, two beams are without CFRP reinforcement, which are used as control beams for the strengthened one, and the other four beams are strengthened with CFRP laminates with different number of layers and spacing. Numerical investigation is conducted on these beams, and comparisons between the available experimental results for these beams and numerical results from the current study are made. Conclusions from these comparisons are presented and discussed. An increase of about 15.6% in the ultimate torque for the solid beam and of about 9.8% in the ultimate torque for the box-section beam is observed after using the CFRP strips. A parametric study is carried out to study the torsional behavior of RC beams having different number of CFRP layers and concrete compressive strength; also U-wrap for the CFRP configuration is investigated.

Shear behaviour of seawater sea-sand coral aggregate concrete beams reinforced with FRP strip stirrups

The preparation of concrete for remote islands or reefs using locally available seawater, sea sand, and coral aggregate can greatly shorten the construction period and mitigate the shortage of river sand and natural gravel resources. This study is the first to experimentally investigate the shear behaviour of seawater sea-sand coral aggregate concrete (SSCAC) beams reinforced with non-corrosive carbon fibre-reinforced polymer (CFRP) strip stirrups. The test parameters included concrete strength, concrete type, and stirrup configuration. The experimental results suggested that CFRP-reinforced SSCAC beams exhibited a brittle shear failure mode because of the sudden CFRP rupture at the bend portions. The ratio of the measured maximum strain to the ultimate tensile strain of the CFRP strip stirrups varied from 36.6% to 47.8%. The critical diagonal shear cracks of SSCAC beams directly penetrated through the coral aggregates and split the aggregates, whereas those in the natural aggregate concrete (NAC) beams bypassed the natural gravel. In this regard, the SSCAC beams exhibited approximately 10% lower shear strength than their NAC counterparts owing to the loss of the aggregate interlocking effect after the occurrence of smooth diagonal shear cracks. The higher the strength grade of SSCAC, the greater the shear strength and service load.

Behavior and Load Capacity of Concrete Slab Reinforced by CFRP Bar and Strengthening by CFRP Laminates

Abstract The most common FRP materials used are carbon fiber reinforced polymers (CFRPs), and glass fiber reinforced polymers (GFRPs). The use of CFRPs has grown rapidly in the construction industry, specifically in structural retrofitting, due to their strengthening property of CFRP. CFRPs are moreover high strength, lightweight, noncorrosive, and easy-to-install materials. In the present study, six reinforced concrete slab specimens included two control specimens reinforced by traditional steel reinforcements and the other reinforced by carbon fiber reinforced polymer CFRP bars without strengthening by laminated CFRP strips. The remaining four specimens are interiorly reinforced by CFRP bars and strengthened by CFRP laminates strips with different scheme layouts named Type 1 and Type 2. The specimens were tested under a uniformly distributed load applied at the top surface area of each specimen up to failure. The parameters considered in the present study are the amount of CFRP bars and CFRP laminates layout. Test results indicated that the strength carrying capacity and failure mode of tested specimens differ based on the steel reinforcement type and the presence of CFRP laminates layout.