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Flexural behavior of RC beams externally reinforced with CFRP composites using various strategies

  • Yousif Jabbar Lafta , Hawraa S. Malik EMAIL logo and Majid Faissal Jassim
Published/Copyright: February 22, 2024
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Open Engineering
From the journal Open Engineering Volume 14 Issue 1

Abstract

The external composite material bonding is an effective and practical method for flexural strengthening of reinforced concrete (RC) beams, providing a large opportunity to develop high-performance and cost-effective structures. Numerous uses exist for carbon fiber-reinforced polymer (CFRP) materials as RC-member strengthening methods. However, issues with bonding and de-bonding continue to be a barrier to this technique's accomplishment. In this research, the CFRP sheets were integrated as an external strengthening material to evaluate their contribution to the flexural performance and so determine how well the CFRP sheets are being used. The experimental work includes one control beam and ten RC beams with CFRP sheets as external strengthening. All beams have the same dimensions: a length of 1.7 m and a sectional area of 20 cm × 25 cm. Experimental tests were carried out with varying CFRP types, lengths, numbers, and arrangements. Each beam’s performance was evaluated in terms of failure mode, ultimate load capacity, ultimate deflection, and a load–deflection curve. The findings demonstrate the effectiveness of CFRP strengthening by demonstrating a considerable improvement in the majority of the study variables. Furthermore, the CFRP strengthening offered an exterior crack-arresting mechanism.

Keywords: flexural behavior; reinforced concrete; composite material; carbon fiber-reinforced polymer

1 Introduction

Many degraded reinforced concrete (RC) structures around the world require reinforcement for a variety of reasons, including their expired design life, probable damage from environmental effects and mechanical activities, extra stringent design requirements, changes in functionality, and initial design and construction mistakes. Several approaches for strengthening concrete members were created based on previous research and design practice, including the use of external bonding of plates, which is helpful for flexural components of the structure. Externally fiber-reinforced polymer (FRP) sheets are becoming more popular in strengthening structures due to their numerous advantages, such as the high ultimate strength of FRP, high elastic modulus, corrosion resistance, a low mass-to-inertia ratio, and a high strength/weight ratio, and a shorter installation time. This is especially true when utilized for complicated-shaped structural elements.

Aramid, glass, and carbon fibers are the most commonly used. Aramid fiber-reinforced polymer (AFRP) and glass fiber-reinforced polymer (GFRP) members are significantly more ductile than carbon fiber-reinforced polymer (CFRP) members. Numerous studies have been made to increase the strength, durability, and stiffness of RC beams reinforced with GFRP and CFRP. In a typical flexural strengthening procedure to increase flexural capacity, FRP is applied longitudinally along the beam axis [1,2].

2 Background

CFRP sheets are now widely used as a strengthening technique for RC members such as columns, beams, beam–column connections, and slabs [3].

Numerous studies have been conducted on the feasibility of using FRP materials to strengthen various structural members; where Attari et al. [4] examined the efficiency of using the external FRP composite as a strengthening technique for RC beams. Seven RC beams strengthened with CFRP or GFRP were applied to two-point loads until failure is analyzed. Beams’ failure modes, strength, ductility, and stiffness are discussed for many strengthening parameters. In addition, an finite element model for predicting the flexural failure of the beams is used; it accurately predicts the beams' behavior under the applied loads. The study also indicated that the use of two layers of GFRP is cost-effective as a strengthening arrangement for RC structures.

Górski et al. [5] discussed the results of mechanical testing on the strengthening of structures. Utilizing the conductivity of carbon fibers, smart textiles may measure strains while monitoring changes in electrical resistance as a result of increasing loads. Also, the primary experiments were conducted on a natural-scale RC beam with carbon fiber-reinforced fabric. The effectiveness of smart textiles was demonstrated in both strengthening and strain monitoring as the load increased.

Kuntal et al. [6] revealed that the beams’ ductility and stiffness can be significantly increased by applying the right arrangement for the near-surface mounted (NSM) strips. Jadooe et al. [7] investigated the flexural behavior of eight RC beams with sheets of CFRP after heating. The study showed that repairing with the CFRP laminate by using NSM systems with cement-or-epoxy-based notches created into the surface of concrete increased the beams’ stiffness and load capacity. The finite-element method was used in this study, and they were capable of predicting the experimental behavior reasonably well.

Obaidat et al. [8] extended the CFRP composites to concrete columns using fillets and chamfers placed at the beam–column intersection to study the structural behavior of cantilever beams. Fourteen beam–column intersections were tested after bonding CFRP sheets only along the beam’s tension zone or extending the CFRP elements to the column surface by making fillets and chamfers at the intersection of the beam–column. The length, width, and layer number of CFRP sheets, and the use of concrete fillets and chamfers all influenced the mechanical behavior of the studied beams. End anchorage with U-shape CFRP composites helped delay the de-bonding of the CFRP sheets and subsequently improved mechanical behavior, particularly for cantilever beams repaired with CFRP extended to the columns’ surfaces.

Amaireh et al. [9] demonstrated the efficacy of CFRP strips as primary or secondary shear reinforcement for RC beams. The CFRP strips perform the same function as the steel stirrups in conjunction with the concrete and steel reinforcement. The studied variables consist of layer number and the area of CFRP strips. The findings demonstrate that CFRP elements can be successfully used in RC beams as internal shear reinforcement. By adding just one 5 cm CFRP strip to the beam sides, the maximum shear strength was increased by 30%; when the shear span was completely reinforced with CFRP strips, the shear capacity was roughly doubled.

Zaki and Rasheed [10] investigated the efficiency of reinforcing six RC beams with four layers of flexural CFRP plus longitudinal GFRP sidebars or side patches to anchor the flexural CFRP sheets used to strengthen RC beams. Three of the six beams have rectangular cross-sections, while the other has a T-cross-section. All beams were applied to two-point loads till failure, and the findings demonstrated that employing CFRP sheets increased the beams’ flexural capacity. The same conclusions were reached when compared to the results of U-wrap anchored samples from other research. Shomali et al. [11] used the NSM method to examine the RC beams' behavior; the beams designed with and without stirrups strengthened in shear. The beams were under two-point loads, and the failure modes, as well as the load–deflection curves, were discussed. The study indicates that the use of CFRP composites leads to improvement of beams’ shear capacity, and the failure occurs because of the rupture of CFRP. Furthermore, when NSM-strengthened beams were compared to reference beams, the ductility decreased for all strengthened beams. Moreover, the stiffness of the strengthened beams with a stirrup was higher than those without a stirrup. The finite element method revealed that the possibility of de-bonding decreases as the concrete strength decreases, and the ultimate strain in CFRP composite reduces when the amount of shear reinforcement increases.

Hassan et al. [12] examined the flexural effectiveness of beams with GFRP reinforcement and CFRP strengthening. Ten GFRP-RC beams have been outfitted and applied to two concentrated loads. The parameters studied were the GFRP reinforcement ratio and the CFRP sheet numbers. The mid-deflection, concrete strains, and size of the beam cracks were measured and compared. The results showed that the mid-deflection and size of cracks were decreased by raising the ratio of GFRP reinforcement and CFRP layer number. Al-Rousan et al. [13] used the CFRP sheet as a longitudinal reinforcement for concrete elements. The objective was to evaluate the CFRP sheet’s contribution to flexural performance in order to determine whether utilizing it as primary or supplementary longitudinal reinforcement is effective. The studied parameters are the CFRP sheet length, CFRP layer number, and strengthening type. The beams’ performance was checked for the maximum load capacity, stiffness, maximum deflection, load–deflection curve, failure mode, ductility index, energy absorption, CFRP strain, and performance factor. The results demonstrate the effectiveness of internal strengthening by demonstrating considerable incensement in the majority of the tested parameters. Internal strengthening creates an external crack-arresting technique, even after having reached the maximum load capacity. Sukanto et al. [14] reviewed different kinds of epoxy and curing methods that are frequently used as composite matrices. The results show that these materials nowadays play a significant role in research, design, production, and recycling.

This research aims to assess the usefulness and impact of CFRP strengthening on the flexural behavior of RC beams. Eleven RC beams with various variables, such as the type, length, and arrangement of CFRP, were constructed and examined under four-point loads.

3 Experimental program

3.1 Description of materials

3.1.1 Concrete

All of the specimens were built with the same concrete mix (1:1.8:2.7 by weight) for cement, fine, and coarse aggregate, with a water-to-cement ratio of 0.47. The maximum size of aggregate used was 20 mm; also, a superplasticizer material has been used as a percentage of the weight of cement in order to enhance the concrete workability. The compressive strength of concrete was 36 MPa; it was measured based on the BS EN 12390-3:2019 by using 100 mm × 200 mm cylinders. The slump of the concrete mixture was 80 mm [15]. The average splitting tensile strength of concrete at 28 days was 2.6 MPa measured by 100 mm × 200 mm cylinders based on ASTM C496/C496M-17 [16]. The average concrete modulus of rapture was 4.1 MPa. According to ACI 318-14 [17], the reinforcement steel bars were N10 and N16 for strips and longitudinal reinforcement, respectively, and their properties are shown in Table 1.

Table 1

Reinforcement properties

Steel bar diameter(mm) Modulus of elasticity (GPa) Ultimate strength (MPa) Yield strength (MPa)
10 199.7 635 490
16 199.9 680 510

3.1.2 Strengthening materials

The use of FRP as an externally bonded systems have received a great deal of attention in recent decades. It can be used to strengthen and repair existing RC structures. Full bonding is typically assumed between the FRP materials and the attached surface of the beams during the design and analysis processes. In contrast, the ideal bond is based on the adhesive shear stiffness [18]. Most structural resin adhesives can achieve excellent bond characteristics. Some epoxy resins, in contrast, have low shear stiffness, which leads to bond slip between the concrete substrate and the FRP material, reducing composite action [1,2]. When the beam was 28 days old, the process of strengthening began, with two types of strengthening used.

  • As shown in Figure 1, a CFRP composite consists of woven carbon fabric (SikaWrap®-300 C) and an epoxy agent (Sikadur®-330 LP). SikaWrap®-300 C is a mid-range strength unidirectional woven carbon fabric that can be installed using either a wet or dry application process. Strengthens RC, masonry, brickwork, and timber elements to improve shear and flexural capacity. The CFRP and epoxy properties, which are provided by the manufacturer, are shown in Tables 2 and 3.

  • Figure 2 shows a CFRP composite consisting of a carbon fabric plate (Sika CarboDur) and an epoxy agent (Sikadur®-30 LP). A pultruded CFRP laminate (Sika CarboDur) is intended to strengthen concrete, masonry, and wood structures. The CFRP plate was attached to the structure using epoxy resin (Sikadur 30 LP) as the adhesive. The CFRP and the epoxy properties are listed in Tables 4 and 5.

Figure 1 Strengthening material.
Figure 1

Strengthening material.

Table 2

Properties of SikaWrap®-300C

Density (g/cm3) Thickness (mm) Width (mm) Elongation at break (%) Tensile strength (MPa) Modulus of elasticity (MPa)
1.82 0.167 500 1.7 4,000 230,000
Table 3

Properties of epoxy resin (Sikadur®-330LP)

Density (kg/l) Tensile strength (N/mm2) Modulus of elasticity (MPa) Elongation at break (%)
1.3 30 3,800 0.9
Figure 2 Strengthening material.
Figure 2

Strengthening material.

Table 4

Properties of carbon fiber (Sika CarboDur, Type S 1012)

Density (g/cm3) Thickness (mm) Width (mm) Modulus of elasticity (MPa) Tensile strength (MPa) Elongation at break (%)
1.60 1.2 100 160,000 2,800 1.69
Table 5

Properties of epoxy resin (Sikadur®-30LP)

Density (kg/l) Tensile strength (MPa) Modulus of elasticity (MPa)
1.65 25 10,000

3.2 Specimen details

Eleven simply supported RC beams under four-point loads were used in the experimental work to find the efficacy of CFRP elements as a strengthening member. Plywood sheets were created and produced for the beams so as to utilize the precision of the specifications and a high-quality concrete surface finish. The experimental beams measured (250 × 200) mm in cross-section and 1,700 mm in length. Longitudinal reinforcement was included for all beams in the form of two N12 bars at the compression and tension surfaces of the beams. Shear-reinforced N10 stirrups were designed to be spaced 80 mm apart along the length of the beams to work in conjunction with CFRP strengthening to resist flexural failure. For all concrete beams, steel reinforcement was embedded into the formwork and supported by the bottom and web concrete cover spacers to achieve the desired cover. Figure 3 depicts the beam dimensions and reinforcing details. The parameters examined were the CFRP layer number of one, two, and three, the CFRP length of 750, 1,000, and 1,500 mm, the CFRP plate width of 100 and 200 mm, the CFRP type of woven and plate, and finally, the arrangement of CFRP as shown in Figures 6–10.

Figure 3 Specimen details and concrete beam preparation.
Figure 3

Specimen details and concrete beam preparation.

3.3 Application and layout of CFRP to beams

Ten of the simply supported beams were cast and strengthened with two types of CFRPs; they were classified into five groups (A, B, C, D, and E) depending on the CFRP arrangement as summarized in Table 6 and Figure 4. One of the beams was used as a control member (T), and the others with CFRP were strengthened in flexure by using various anchorage arrangements as discussed in Sections 3.3.1–3.3.5. Depending on the studied case, the CFRP was trimmed to the appropriate width and length. For each beam, first, the beams were cast and left for 28 days. The bonding region of the beams was cleaned by an air vacuum cleaner in order to eliminate any undesired particles. Finally, a uniform epoxy layer was put over the contact zone, and the CFRP was set on top of the epoxy. The strengthened beams were left at room temperature for 7 days, based on the manufacturer’s instructions for curing and hardening the epoxy before use. Figure 5 shows the beam through the surface preparation.

Table 6

Dimension details of the specimens

Beam designation Group No. of CFRP layers Type of CFRP Length of CFRP (cm) Width of CFRP (mm) Side no. of strengthening
Control (T) — — — — —
T-W-1L-75 A 1 W 75 200 Bottom side
T-W-1L-100 1 W 100 200 Bottom side
T-W-1L-150 1 W 150 200 Bottom side
T-W-1L-150 B 1 W 150 200 Bottom side
T-W-2L 2 W 150 200 Bottom side
T-W-3L 3 W 150 200 Bottom side
T-W-1L-150 C 1 W 150 200 Bottom side
T-W-U-150 1 W 150 700 Three sides (U-shape)
T-P-1L D 1 Plate 150 100 Bottom side
T-P-2L 1 Plate 150 200 Bottom side
T-W-R E 1 Woven At the bottom and around the ends of the beam
Figure 4 Beams’ details.
Figure 4

Beams’ details.

Figure 5 Surface preparation for the tested beams.
Figure 5

Surface preparation for the tested beams.

3.3.1 Specimens T-W-1L-75, T-W-1L-100, and T-W-1L-100

Beams (T-W-1L-75), (T-W-1L-100), and (T-W-1L-150) were strengthened with a single layer of unidirectional CFRP (SikaWrap®-300 C). Table 6 shows that the CFRP woven was cut into sheets that were 200 mm wide and varied in lengths by 750, 1,000, and 1,500 mm, and they were attached to the tension face of the beam only (Figure 6).

Figure 6 Beams with various CFRP lengths.
Figure 6

Beams with various CFRP lengths.

3.3.2 Specimens T-W-1L-150, T-W-2L, and T-W-3L

Beams T-W-1L-150, T-W-2L, and T-W-3L were fortified in flexure with different CFRP wrap layers. However, the design for those three beams involved using one, two, and three CFRP wrap layers, respectively. Table 6 shows that the CFRP woven was cut into sections with dimensions of 200 mm × 1,500 mm. After roughening and cleaning the concrete-bonded region with an air vacuum cleaner, the initial epoxy layer was uniformly settled over the contact zone, and the CFRP woven was laid on top of the epoxy. For beams T-W-2L and T-W-3L, the second epoxy layer was put over the first layer of CFRP woven with a uniform distribution before applying the other CFRP woven layers (Figure 7). The CFRP wraps of these beams were placed at the bottom face only.

Figure 7 Beams with different numbers of CFRP layers.
Figure 7

Beams with different numbers of CFRP layers.

3.3.3 Specimen T-W-U-150

The T-W-U-150 beam was strengthened with a single layer of unidirectional CFRP wrap with a length of 1,500 mm attached to the bottom and to the two side faces of the beam as a U-shape (Figure 8).

Figure 8 Beam with U-shape of CFRP woven.
Figure 8

Beam with U-shape of CFRP woven.

3.3.4 Specimens T-P-1L and T-P-2L

Beams T-P-1L and T-P-2L were strengthened with CFRP plates in the flexure area. The design for beam T-P-1L consisted of using one standard CFRP plate with a 100 mm width and 1.5 m length, while the T-P-2L beam involved using two standard CFRP plates (Figure 9).

Figure 9 Beam with CFRP plates for group D.
Figure 9

Beam with CFRP plates for group D.

3.3.5 Specimen T-W-R

Beam T-W-R was strengthened with CFRP wrap in the flexure area. The design for beam T-W-R consisted of a CFRP woven wrap around the beam ends with a width of 300 mm (Figure 10).

Figure 10 Beam with CFRP composites at the bottom and the ends.
Figure 10

Beam with CFRP composites at the bottom and the ends.

4 Results and discussion

The experimental results were discussed with respect to load–deflection behavior, improvement of performance, and failure mode. All beams were subjected to two concentrated loads by a testing machine with a load capacity of 500 kN, as shown in Figure 11. The load was put on with a constant increment of 5 kN per minute until the beam failed, at which point the ultimate load was measured. The ultimate deflections were also measured using a least count located in the beams’ mid-span. Table 7 shows an overview of the experimental data.

Figure 11 Testing machine of the simply supported beam.
Figure 11

Testing machine of the simply supported beam.

Table 7

Summary of the beam results

Specimen designation Max. load (kN) Increase of max. load (Ti − T0)/T0 (%) Max. def. (mm) Increase of max Def. (Ti − T0)/T0 (%) Failure mode
Control (T) 110 — 14 — Concrete crashing
T-W-1L-75 127.5 15.9 10.69 23.6 Delaminating of CFRP
T-W-1L-100 135 22.7 9.04 35.4 Delaminating of CFRP
T-W-1L-150 139 26.4 10.62 24.1 Delaminating of CFRP
T-W-2L 150 36.4 9.27 33.8 Delaminating of CFRP
T-W-3L 160 45.5 8.2 41.4 Delaminating of CFRP
T-W-U-150 155 40.9 10.79 22.9 CFRP rupture
T-P-1L 143 30 8.88 36.57 Delaminating of CFRP
T-P-2L 157 42.7 9.6 31.4 Delaminating of CFRP
T-W-R 160 45.5 11.06 21 Delaminating of CFRP

4.1 Load–deflection

Table 7 summarizes the beams' flexural behavior in relation to the ultimate loading capacity and related mid-deflection. Where the increase in ultimate loads ranged from 15.9 to 26.4% and 26.4 to 45.5%, respectively, based on the various strengthening lengths and layer numbers of CFRP sheets. CFRP woven in a U-shape raises the ultimate load by 40.9%. Furthermore, the use of CFRP plates increases the ultimate load from 30 to 42.7%, and finally, the use of CFRP at the beam ends, in addition to the bottom CFRP plate, improves the ultimate load capacity by 45.5% in compression with the control member. Figure 12 depicts load vs. deflection at mid-span of all beams. The load–deflection curves of the beams with a single layer of CFRP of three different lengths are presented to demonstrate the influence of CFRP woven length (Figure 12(a)), the effect of the number of CFRP sheets for beams strengthened with 150 mm length of CFRP (Figure 12(b)), the effect of beam strengthened with U-shaped CFRP woven (Figure 12(c)), and the effect of CFRP plate width for specimens with one layer of CFRP plate (Figure 12(d)). There is a slight change in the mechanical behavior of all beams, as illustrated in Figure 12. There are two stages to the relationship of the load–deflection: The first step is to go from zero loadings to pre-cracking, which is when the load is drastically increased with only a minor rise in deflection. Following the formation of the initial flexural crack, the load is gradually raised as deflection instantly increases. The flexural crack formation reduced beam stiffness, so the CFRP sheets withstand the applied load. When compared to the control beam, the slope of both stages of the curve raised significantly and marginally for beams with CFRP sheets. The findings show that an increment in length, layer number, and width of the CFRP sheet enhances load and deflection capacity once the primary flexural fracture is formed. Also, the results cleared that the adding of CFRP sheets improved the ultimate strength and ultimate deflection.

Figure 12 Load–deflection curves of all tested beams. (a) Group A. (b) Group B. (c) Group C. (d) Group D. (e) Group E.
Figure 12

Load–deflection curves of all tested beams. (a) Group A. (b) Group B. (c) Group C. (d) Group D. (e) Group E.

4.2 Ultimate load capacity and deflection

The maximum load and deflection of the examined beams were standardized in relation to the control beam (Figure 13(a and b)). According to Figure 13, the load improvement for beams with one CFRP layer and lengths of 75 cm, 100 cm, and 150 cm was 15.9, 22.7, and 26.4%, respectively. Whereas the increase in maximum load for beams with one, two, and three CFRP layers is 26.4, 36.4, and 45.5%, respectively. The load improvement for beams with 100 and 200 mm width of FRP plate was 30 and 42.7%, respectively. In contrast, the increase in the maximum load for one layer of CFRP woven is 40.9% for beams with CFRP at three sides. Finally, improvement at ultimate load and corresponding deflection are 45.5 and 21% for beams with tension CFRP plate and ends CFRP woven. According to the findings, the use of the CFRP sheets was an effective method for strengthening. The best experience was when using three layers of CFRP woven (T-W-3L-150), as it gave the highest load capacity and the lowest deflection. The beam with a CFRP plate at the bottom and CFRP woven at the ends (T-W-1L-R) has the same ultimate load as beam T-W-3L-150 but has a greater deflection.

Figure 13 Ultimate load and deflection relative to the control beam. (a) Maximum load. (b) Maximum deflection.
Figure 13

Ultimate load and deflection relative to the control beam. (a) Maximum load. (b) Maximum deflection.

4.3 Cracking and failure mode

Figure 14 displays the control beam’s failure modes and cracking patterns, as well as the beams with CFRP sheets. The initial flexural crack created at the mid-span on the tension zone of the beams was followed by de-bonding of the CFRP sheet. The following is a description of the de-bonding failure: Because flexural cracks occurred in the region with a pure moment as the load grew, the bond between the concrete and FRP began to break at a specified loading level, and the failure then spread to the shear span, causing the majority of the CFRP sheets to separate from the RC beam. As is evident, the bond between the CFRP and the surface of the concrete is insufficient to prevent the composites with CFRP sheets from rupturing. As a result, the bond strength of the CFRP–concrete determines the mode of failure. It was recognized that the length, type, and arrangement of CFRP sheets had a noticeable effect on the cracks’ numbers, length, and distribution. Figure 14(a) shows that the distribution and number of cracks increased as the length of CFRP material increased, but the length of the cracks (from the bottom to the top side of the neutral axis of the cracking part) lowered. Figure 14(b) shows that as the number of strengthened layers increased, the distribution, length, and number of cracks also decreased. This is due to the CFRP sheet’s capacity to provide enough development length to bridge flexural cracks. Additionally, the increasing CFRP layers had a significant impact on reducing the length and number of cracks. This may be explained by the external CFRP sheet’s ability to prevent beams from delaminating, which results in exceptional behavior in the flexural crack-arresting process. Figure 14(c) shows that as the CFRP plate width is decreased, the number of cracks and damages increase, and the damage is also greater than if a CFRP weave is used as the beam (T-W-1L-150). In the case of the application of CFRP sheets on three sides of the beam T-W-U-150, the beam failure mode transferred from FRP delamination from the concrete substrate to FRP rupture in the constant moment area. Figure 14 depicts two common modes of failure. Finally, the failure of the reinforced beam in Figure 14(e) was caused by the de-bonding of the CFRP plate coupled with horizontal cracking in the tension zone at the beam mid-span. This type of failure occurs due to the sudden propagation of horizontal cracks in the region of the concrete–steel bond. This kind of crack occurs along the concrete steel interface, which is the weakest surface, which leads to the beam failure as soon as the cracks open and separate the cover of concrete from the whole beam.

Figure 14 Failure mode of the tested beams. (a) Group A, (b) Group B, (c) Group C, (d) Group D, and (e) Group E.
Figure 14

Failure mode of the tested beams. (a) Group A, (b) Group B, (c) Group C, (d) Group D, and (e) Group E.

5 Conclusion

One reference and 10 beams strengthened with CFRP elements bonded with an epoxy were examined under a four-point load, and the results of the failure of those 11 RC beams have been discussed. This study investigates the efficiency of RC beams strengthened with CFRP elements of various lengths, types, and configurations. Table 1 contains a summary of the tested results.

The following are the key conclusions of this study:

  1. The use of CFRP woven along the beam tension region halts flexural cracks and enhances the serviceability and performance of the studded beams. The efficacy of CFRP woven into the flexural crack bridging improved as the CFRP length increased.

  2. According to the test results, the load-carrying capability of the RC beams improved with the layer number of the CFRP woven.

  3. Comparing the results of the beams strengthened by CFRP plates with the control beam showed that the CFRP plates increased the beam’s load-carrying capacity, especially for beams with two plates.

  4. The CFRP sheets had a significant impact on the length and width of cracks.

  5. All the test beams failed because of de-bonding of CFRP sheets, with the exception of the U-shaped CFRP beam, which failed due to carbon fiber woven rupture.

  6. The maximum increments in the maximum load of the beams were 45.5% when flexural CFRP strengthening was anchored with three CFRP woven (T-W-3L-150) and with a plate in addition to the CFRP woven at the ends (T-w-R).

  7. Lastly, the use of CFRP woven at the ends of the beam causes failure only at the mid-span but is ineffective in delaying premature de-bonding.

  1. Funding information: The authors declare that the manuscript was done depending on the personal effort of the authors, and there is no funding effort from any side or organization.

  2. Conflict of interest: Authors state no conflict of interest.

  3. Data availability statement: Most datasets generated and analyzed in this study are comprised in this submitted manuscript. The other datasets are available on reasonable request from the corresponding author with the attached information.

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Received: 2023-06-14
Revised: 2023-07-11
Accepted: 2023-07-22
Published Online: 2024-02-22

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Regular Articles
  2. Methodology of automated quality management
  3. Influence of vibratory conveyor design parameters on the trough motion and the self-synchronization of inertial vibrators
  4. Application of finite element method in industrial design, example of an electric motorcycle design project
  5. Correlative evaluation of the corrosion resilience and passivation properties of zinc and aluminum alloys in neutral chloride and acid-chloride solutions
  6. Will COVID “encourage” B2B and data exchange engineering in logistic firms?
  7. Influence of unsupported sleepers on flange climb derailment of two freight wagons
  8. A hybrid detection algorithm for 5G OTFS waveform for 64 and 256 QAM with Rayleigh and Rician channels
  9. Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy
  10. Exploring the potential of ammonia and hydrogen as alternative fuels for transportation
  11. Impact of insulation on energy consumption and CO2 emissions in high-rise commercial buildings at various climate zones
  12. Advanced autopilot design with extremum-seeking control for aircraft control
  13. Adaptive multidimensional trust-based recommendation model for peer to peer applications
  14. Effects of CFRP sheets on the flexural behavior of high-strength concrete beam
  15. Enhancing urban sustainability through industrial synergy: A multidisciplinary framework for integrating sustainable industrial practices within urban settings – The case of Hamadan industrial city
  16. Advanced vibrant controller results of an energetic framework structure
  17. Application of the Taguchi method and RSM for process parameter optimization in AWSJ machining of CFRP composite-based orthopedic implants
  18. Improved correlation of soil modulus with SPT N values
  19. Technologies for high-temperature batch annealing of grain-oriented electrical steel: An overview
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  25. Thermal analysis of Fe3O4–Cu/water over a cone: a fractional Maxwell model
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  31. Evaluation of the creep strength of samples produced by fused deposition modeling
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  38. Relationship between indoor environmental quality and guests’ comfort and satisfaction at green hotels: A comprehensive review
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  65. Experimental investigation on strengthening lap joints subjected to bending in glulam timber beams using CFRP sheets
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  90. Studying the effect of using CFRP warping on strength of husk rice concrete columns
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https://doi.org/10.1515/eng-2022-0492
Keywords for this article
flexural behavior; reinforced concrete; composite material; carbon fiber-reinforced polymer
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Methodology of automated quality management
  3. Influence of vibratory conveyor design parameters on the trough motion and the self-synchronization of inertial vibrators
  4. Application of finite element method in industrial design, example of an electric motorcycle design project
  5. Correlative evaluation of the corrosion resilience and passivation properties of zinc and aluminum alloys in neutral chloride and acid-chloride solutions
  6. Will COVID “encourage” B2B and data exchange engineering in logistic firms?
  7. Influence of unsupported sleepers on flange climb derailment of two freight wagons
  8. A hybrid detection algorithm for 5G OTFS waveform for 64 and 256 QAM with Rayleigh and Rician channels
  9. Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy
  10. Exploring the potential of ammonia and hydrogen as alternative fuels for transportation
  11. Impact of insulation on energy consumption and CO2 emissions in high-rise commercial buildings at various climate zones
  12. Advanced autopilot design with extremum-seeking control for aircraft control
  13. Adaptive multidimensional trust-based recommendation model for peer to peer applications
  14. Effects of CFRP sheets on the flexural behavior of high-strength concrete beam
  15. Enhancing urban sustainability through industrial synergy: A multidisciplinary framework for integrating sustainable industrial practices within urban settings – The case of Hamadan industrial city
  16. Advanced vibrant controller results of an energetic framework structure
  17. Application of the Taguchi method and RSM for process parameter optimization in AWSJ machining of CFRP composite-based orthopedic implants
  18. Improved correlation of soil modulus with SPT N values
  19. Technologies for high-temperature batch annealing of grain-oriented electrical steel: An overview
  20. Assessing the need for the adoption of digitalization in Indian small and medium enterprises
  21. A non-ideal hybridization issue for vertical TFET-based dielectric-modulated biosensor
  22. Optimizing data retrieval for enhanced data integrity verification in cloud environments
  23. Performance analysis of nonlinear crosstalk of WDM systems using modulation schemes criteria
  24. Nonlinear finite-element analysis of RC beams with various opening near supports
  25. Thermal analysis of Fe3O4–Cu/water over a cone: a fractional Maxwell model
  26. Radial–axial runner blade design using the coordinate slice technique
  27. Theoretical and experimental comparison between straight and curved continuous box girders
  28. Effect of the reinforcement ratio on the mechanical behaviour of textile-reinforced concrete composite: Experiment and numerical modeling
  29. Experimental and numerical investigation on composite beam–column joint connection behavior using different types of connection schemes
  30. Enhanced performance and robustness in anti-lock brake systems using barrier function-based integral sliding mode control
  31. Evaluation of the creep strength of samples produced by fused deposition modeling
  32. A combined feedforward-feedback controller design for nonlinear systems
  33. Effect of adjacent structures on footing settlement for different multi-building arrangements
  34. Analyzing the impact of curved tracks on wheel flange thickness reduction in railway systems
  35. Review Articles
  36. Mechanical and smart properties of cement nanocomposites containing nanomaterials: A brief review
  37. Applications of nanotechnology and nanoproduction techniques
  38. Relationship between indoor environmental quality and guests’ comfort and satisfaction at green hotels: A comprehensive review
  39. Communication
  40. Techniques to mitigate the admission of radon inside buildings
  41. Erratum
  42. Erratum to “Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy”
  43. Special Issue: AESMT-3 - Part II
  44. Integrated fuzzy logic and multicriteria decision model methods for selecting suitable sites for wastewater treatment plant: A case study in the center of Basrah, Iraq
  45. Physical and mechanical response of porous metals composites with nano-natural additives
  46. Special Issue: AESMT-4 - Part II
  47. New recycling method of lubricant oil and the effect on the viscosity and viscous shear as an environmentally friendly
  48. Identify the effect of Fe2O3 nanoparticles on mechanical and microstructural characteristics of aluminum matrix composite produced by powder metallurgy technique
  49. Static behavior of piled raft foundation in clay
  50. Ultra-low-power CMOS ring oscillator with minimum power consumption of 2.9 pW using low-voltage biasing technique
  51. Using ANN for well type identifying and increasing production from Sa’di formation of Halfaya oil field – Iraq
  52. Optimizing the performance of concrete tiles using nano-papyrus and carbon fibers
  53. Special Issue: AESMT-5 - Part II
  54. Comparative the effect of distribution transformer coil shape on electromagnetic forces and their distribution using the FEM
  55. The complex of Weyl module in free characteristic in the event of a partition (7,5,3)
  56. Restrained captive domination number
  57. Experimental study of improving hot mix asphalt reinforced with carbon fibers
  58. Asphalt binder modified with recycled tyre rubber
  59. Thermal performance of radiant floor cooling with phase change material for energy-efficient buildings
  60. Surveying the prediction of risks in cryptocurrency investments using recurrent neural networks
  61. A deep reinforcement learning framework to modify LQR for an active vibration control applied to 2D building models
  62. Evaluation of mechanically stabilized earth retaining walls for different soil–structure interaction methods: A review
  63. Assessment of heat transfer in a triangular duct with different configurations of ribs using computational fluid dynamics
  64. Sulfate removal from wastewater by using waste material as an adsorbent
  65. Experimental investigation on strengthening lap joints subjected to bending in glulam timber beams using CFRP sheets
  66. A study of the vibrations of a rotor bearing suspended by a hybrid spring system of shape memory alloys
  67. Stability analysis of Hub dam under rapid drawdown
  68. Developing ANFIS-FMEA model for assessment and prioritization of potential trouble factors in Iraqi building projects
  69. Numerical and experimental comparison study of piled raft foundation
  70. Effect of asphalt modified with waste engine oil on the durability properties of hot asphalt mixtures with reclaimed asphalt pavement
  71. Hydraulic model for flood inundation in Diyala River Basin using HEC-RAS, PMP, and neural network
  72. Numerical study on discharge capacity of piano key side weir with various ratios of the crest length to the width
  73. The optimal allocation of thyristor-controlled series compensators for enhancement HVAC transmission lines Iraqi super grid by using seeker optimization algorithm
  74. Numerical and experimental study of the impact on aerodynamic characteristics of the NACA0012 airfoil
  75. Effect of nano-TiO2 on physical and rheological properties of asphalt cement
  76. Performance evolution of novel palm leaf powder used for enhancing hot mix asphalt
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  78. Flexural behavior of RC beams externally reinforced with CFRP composites using various strategies
  79. Influence of fiber types on the properties of the artificial cold-bonded lightweight aggregates
  80. Experimental investigation of RC beams strengthened with externally bonded BFRP composites
  81. Generalized RKM methods for solving fifth-order quasi-linear fractional partial differential equation
  82. An experimental and numerical study investigating sediment transport position in the bed of sewer pipes in Karbala
  83. Role of individual component failure in the performance of a 1-out-of-3 cold standby system: A Markov model approach
  84. Implementation for the cases (5, 4) and (5, 4)/(2, 0)
  85. Center group actions and related concepts
  86. Experimental investigation of the effect of horizontal construction joints on the behavior of deep beams
  87. Deletion of a vertex in even sum domination
  88. Deep learning techniques in concrete powder mix designing
  89. Effect of loading type in concrete deep beam with strut reinforcement
  90. Studying the effect of using CFRP warping on strength of husk rice concrete columns
  91. Parametric analysis of the influence of climatic factors on the formation of traditional buildings in the city of Al Najaf
  92. Suitability location for landfill using a fuzzy-GIS model: A case study in Hillah, Iraq
  93. Hybrid approach for cost estimation of sustainable building projects using artificial neural networks
  94. Assessment of indirect tensile stress and tensile–strength ratio and creep compliance in HMA mixes with micro-silica and PMB
  95. Density functional theory to study stopping power of proton in water, lung, bladder, and intestine
  96. A review of single flow, flow boiling, and coating microchannel studies
  97. Effect of GFRP bar length on the flexural behavior of hybrid concrete beams strengthened with NSM bars
  98. Exploring the impact of parameters on flow boiling heat transfer in microchannels and coated microtubes: A comprehensive review
  99. Crumb rubber modification for enhanced rutting resistance in asphalt mixtures
  100. Special Issue: AESMT-6
  101. Design of a new sorting colors system based on PLC, TIA portal, and factory I/O programs
  102. Forecasting empirical formula for suspended sediment load prediction at upstream of Al-Kufa barrage, Kufa City, Iraq
  103. Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide
  104. Sediment transport modelling upstream of Al Kufa Barrage
  105. Study of energy loss, range, and stopping time for proton in germanium and copper materials
  106. Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant
  107. Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars
  108. Sustainable road paving: Enhancing concrete paver blocks with zeolite-enhanced cement
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  117. Measurements of induced vibrations due to steel pipe pile driving in Al-Fao soil: Effect of partial end closure
  118. Experimental and numerical studies of ballistic resistance of hybrid sandwich composite body armor
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  120. Optimal design of mechanical performances of asphalt mixtures comprising nano-clay additives
  121. Advancing seismic performance: Isolators, TMDs, and multi-level strategies in reinforced concrete buildings
  122. Predicted evaporation in Basrah using artificial neural networks
  123. Energy management system for a small town to enhance quality of life
  124. Numerical study on entropy minimization in pipes with helical airfoil and CuO nanoparticle integration
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  126. Thermal buckling analysis for hybrid and composite laminated plate by using new displacement function
  127. Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene
  128. Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site
  129. The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials
  130. Seismic resilience: Innovations in structural engineering for earthquake-prone areas
  131. Automatic human identification using fingerprint images based on Gabor filter and SIFT features fusion
  132. Performance of GRKM-method for solving classes of ordinary and partial differential equations of sixth-orders
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  134. Production of sustainable concrete with treated cement kiln dust and iron slag waste aggregate
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  136. A comparative analysis of the energy dissipation efficiency of various piano key weir types
  137. Special Issue: Transport 2022 - Part II
  138. Variability in road surface temperature in urban road network – A case study making use of mobile measurements
  139. Special Issue: BCEE5-2023
  140. Evaluation of reclaimed asphalt mixtures rejuvenated with waste engine oil to resist rutting deformation
  141. Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag
  142. Investigating seismic response in adjacent structures: A study on the impact of buildings’ orientation and distance considering soil–structure interaction
  143. Improvement of porosity of mortar using polyethylene glycol pre-polymer-impregnated mortar
  144. Three-dimensional analysis of steel beam-column bolted connections
  145. Assessment of agricultural drought in Iraq employing Landsat and MODIS imagery
  146. Performance evaluation of grouted porous asphalt concrete
  147. Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method
  148. Effect of waste tire products on some characteristics of roller-compacted concrete
  149. Studying the lateral displacement of retaining wall supporting sandy soil under dynamic loads
  150. Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)
  151. Behavior of soil reinforced with micropiles
  152. Possibility of production high strength lightweight concrete containing organic waste aggregate and recycled steel fibers
  153. An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials
  154. Forecasting changes in precipitation and temperatures of a regional watershed in Northern Iraq using LARS-WG model
  155. Experimental investigation of dynamic soil properties for modeling energy-absorbing layers
  156. Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams
  157. An experimental study on the tensile properties of reinforced asphalt pavement
  158. Self-sensing behavior of hot asphalt mixture with steel fiber-based additive
  159. Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers
  160. Optimizing asphalt binder performance with various PET types
  161. Investigation of the hydraulic characteristics and homogeneity of the microstructure of the air voids in the sustainable rigid pavement
  162. Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study
  163. Special Issue: AESMT-7 - Part I
  164. Preparation and investigation of cobalt nanoparticles by laser ablation: Structure, linear, and nonlinear optical properties
  165. Seismic analysis of RC building with plan irregularity in Baghdad/Iraq to obtain the optimal behavior
  166. The effect of urban environment on large-scale path loss model’s main parameters for mmWave 5G mobile network in Iraq
  167. Formatting a questionnaire for the quality control of river bank roads
  168. Vibration suppression of smart composite beam using model predictive controller
  169. Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete
  170. In-depth analysis of critical factors affecting Iraqi construction projects performance
  171. Behavior of container berth structure under the influence of environmental and operational loads
  172. Energy absorption and impact response of ballistic resistance laminate
  173. Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs
  174. Effect of surface roughness on interface shear strength parameters of sandy soils
  175. Evaluating the interaction for embedded H-steel section in normal concrete under monotonic and repeated loads
  176. Estimation of the settlement of pile head using ANN and multivariate linear regression based on the results of load transfer method
  177. Enhancing communication: Deep learning for Arabic sign language translation
  178. A review of recent studies of both heat pipe and evaporative cooling in passive heat recovery
  179. Effect of nano-silica on the mechanical properties of LWC
  180. An experimental study of some mechanical properties and absorption for polymer-modified cement mortar modified with superplasticizer
  181. Digital beamforming enhancement with LSTM-based deep learning for millimeter wave transmission
  182. Developing an efficient planning process for heritage buildings maintenance in Iraq
  183. Design and optimization of two-stage controller for three-phase multi-converter/multi-machine electric vehicle
  184. Evaluation of microstructure and mechanical properties of Al1050/Al2O3/Gr composite processed by forming operation ECAP
  185. Calculations of mass stopping power and range of protons in organic compounds (CH3OH, CH2O, and CO2) at energy range of 0.01–1,000 MeV
  186. Investigation of in vitro behavior of composite coating hydroxyapatite-nano silver on 316L stainless steel substrate by electrophoretic technic for biomedical tools
  187. A review: Enhancing tribological properties of journal bearings composite materials
  188. Improvements in the randomness and security of digital currency using the photon sponge hash function through Maiorana–McFarland S-box replacement
  189. Design a new scheme for image security using a deep learning technique of hierarchical parameters
  190. Special Issue: ICES 2023
  191. Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements
  192. Visualizing sustainable rainwater harvesting: A case study of Karbala Province
  193. Geogrid reinforcement for improving bearing capacity and stability of square foundations
  194. Evaluation of the effluent concentrations of Karbala wastewater treatment plant using reliability analysis
  195. Adsorbent made with inexpensive, local resources
  196. Effect of drain pipes on seepage and slope stability through a zoned earth dam
  197. Sediment accumulation in an 8 inch sewer pipe for a sample of various particles obtained from the streets of Karbala city, Iraq
  198. Special Issue: IETAS 2024 - Part I
  199. Analyzing the impact of transfer learning on explanation accuracy in deep learning-based ECG recognition systems
  200. Effect of scale factor on the dynamic response of frame foundations
  201. Improving multi-object detection and tracking with deep learning, DeepSORT, and frame cancellation techniques
  202. The impact of using prestressed CFRP bars on the development of flexural strength
  203. Assessment of surface hardness and impact strength of denture base resins reinforced with silver–titanium dioxide and silver–zirconium dioxide nanoparticles: In vitro study
  204. A data augmentation approach to enhance breast cancer detection using generative adversarial and artificial neural networks
  205. Modification of the 5D Lorenz chaotic map with fuzzy numbers for video encryption in cloud computing
  206. Special Issue: 51st KKBN - Part I
  207. Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection
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