scholarly journals Strength Degradation in Curved Fiber-reinforced Polymer (FRP) Bars Used as Concrete Reinforcement

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1653
Author(s):  
Thanongsak Imjai ◽  
Reyes Garcia ◽  
Maurizio Guadagnini ◽  
Kypros Pilakoutas
Keyword(s):  
Tensile Strength ◽  
Structural Damage ◽  
Mechanical Performance ◽  
Failure Criteria ◽  
Strength Degradation ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
Frp Bars

Steel reinforcements in concrete tend to corrode and this process can lead to structural damage. Fiber-reinforced polymer (FRP) reinforcements represent a viable alternative for structures exposed to aggressive environments and have many possible applications where superior corrosion resistance properties are required. The use of FRP rebars as internal reinforcements for concrete, however, is limited to specific structural elements and does not yet extend to the whole structure. The reason for this relates to the limited availability of curved or shaped reinforcing FRP elements on the market, as well as their reduced structural performance. This article presents a state-of-the art review on the strength degradation of curved FRP composites, and also assesses the performance of existing predictive models for the bend capacity of FRP reinforcements. Previous research has shown that the mechanical performance of bent portions of FRP bars significantly reduces under a multiaxial combination of stresses. Indeed, the tensile strength of bent FRP bars can be as low as 25% of the maximum tensile strength developed in a straight counterpart. In a significant number of cases, the current design recommendations for concrete structures reinforced with FRP were found to overestimate the bend capacity of FRP bars. A more accurate and practical predictive model based on the Tsai–Hill failure criteria is also discussed. This review article also identifies potential challenges and future directions of research for exploring the use of curved/shaped FRP composites in civil engineering applications.

scholarly journals Strength Degradation in Curved FRP bars as Concrete Reinforcement

2020 ◽  
Author(s):  
Thanongsak Imjai ◽  
Reyes Garcia ◽  
Maurizio Guadagnini ◽  
Kypros Pilakoutas
Keyword(s):  
Tensile Strength ◽  
Structural Damage ◽  
Mechanical Performance ◽  
Failure Criteria ◽  
Strength Degradation ◽  
Future Research ◽  
Frp Composites ◽  
Current Design ◽  
Frp Reinforcement ◽  
Superior Corrosion Resistance

Steel reinforcement in concrete has the tendency to corrode and this process can lead to structural damage. FRP reinforcement represents a viable alternative for structures exposed to aggressive environments and has many possible applications where superior corrosion resistance properties are required. The use of FRP rebars as internal reinforcements for concrete, however, is limited to specific structural elements and does not yet extend to the whole structure. The reasons for this relate to the limited availability of curved or shaped reinforcing elements on the market and their reduced structural performance. Various studies, in fact, have shown that the mechanical performance of bent portions of composite bars is reduced significantly under a multiaxial combination of stresses and that the tensile strength can be as low as 25% of the maximum tensile strength that can be developed in the straight part. In a significant number of cases, the current design recommendations for concrete structures reinforced with FRP, however, were found to overestimate the bend capacity of FRP rebar. This paper presents the state-of-the art review of the research works on the strength degradation in curved FRP composites and highlighted the performance of exiting predictive models for the bend capacity of FRP reinforcement. Recent practical predictive model based on the Tsai-Hill failure criteria by considering the material at marcromechanical level is also discussed and highlighted. The review also identifies the challenges and highlights the future directions of research to explore the use of shaped FRP composites in civil engineering applications and the trends for future research in this area.

scholarly journals The effect of temperature on the mechanical properties of hybrid FRP bars applicable for the reinforcing of concrete structures

2020 ◽  
Vol 322 ◽  
pp. 01029
Author(s):  
Karolina Ogrodowska ◽  
Karolina Łuszcz ◽  
Andrzej Garbacz
Keyword(s):  
Mechanical Properties ◽  
Carbon Fibers ◽  
Concrete Structures ◽  
Fiber Reinforced Polymer ◽  
Effect Of Temperature ◽  
Fiber Reinforced ◽  
Reinforcing Bars ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
Frp Bars

One of the most common causes of the deterioration of concrete structures is the corrosion of steel reinforcement. Reinforcement made from fiber reinforced polymers (FRP) is considered to be an attractive substitution for traditional reinforcement. The most popular FRP reinforcing bars are made of glass fibers. Basalt fiber reinforced polymer (BFRP) is a relatively new material for reinforcing bars. The main drawback of BFRP bars is their low modulus of elasticity. A new type of bar made from hybrid fiber reinforced polymer (HFRP) in which a proportion of the basalt fibers are replaced with carbon fibers can be considered as a solution to this issue; such a bar is presented in this work. The HFRP bars might be treated as a relatively simple modification to previously produced BFRP bars. A different technical characteristic of the fibre reinforced polymer makes the designing of structures with FRP reinforcement differ from conventional reinforced concrete design. Therefore, it is necessary to identify the differences and limitations of their use in concrete structures, taking into account their material and geometric features. Despite the predominance of FRP composites in such aspects as corrosion resistance, high tensile strength, and significant weight reductions of structures – it is necessary to consider the behavior of FRP composites at elevated temperatures. In this paper, the effect of temperature on the mechanical properties of FRP bars was investigated. Three types of FRP bar were tested: BFRP, HFRP in which 25% of basalt fibers were replaced with carbon fibers and nHFRP in which epoxy resin was additionally modified with a nanosilica admixture. The mechanical properties were determined using ASTM standard testing for transverse shear strength. The tests were performed at -20°C, +20°C, +80°C for three diameters of each types of bar.

Performance Evaluations of Carbon/Glass Hybrid Polymer Composites

2014 ◽  
Vol 980 ◽  
pp. 8-12 ◽  
Author(s):  
Chye Lih Tan ◽  
Azwan Iskandar Azmi ◽  
Noorhafiza Muhammad
Keyword(s):  
Glass Fiber ◽  
Polymer Composites ◽  
Mechanical Performance ◽  
Hybrid Composites ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Glass Fiber Reinforced Polymer ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced

In this work, the influence of hybrid effect on carbon and glass fiber reinforced polymer (FRP) on the mechanical performance for structural application was studied. The hybrid fiber reinforced polymer (FRP) composites made from woven E-glass and carbon fibers with epoxy resin. The FRP hybrid composites were fabricated using vacuum-assisted resin transfer moulding process, which is capable of producing constant thickness with high volume fractions of composite panels compared to that of traditional wet hand lay-up method. Mechanical performance of the FRP hybrid composites were evaluated against full carbon or glass fiber reinforced polymer composites. Important properties such as tensile strength, flexural strength and volume fraction of reinforcement were determined according to the ASTM standards. It was found that the mechanical properties of carbon-glass hybrid composites exhibited significant improvement in term of strength and strain respectively compared to that of full glass FRP composites and full carbon FRP composites.

scholarly journals Compressive Strength of Modified FRP Hybrid Bars

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1898
Author(s):  
Marek Urbański
Keyword(s):  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Basalt Fiber ◽  
Test Method ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Free Length ◽  
Compression Properties ◽  
Reinforced Polymer ◽  
Frp Bars

A new type of HFRP hybrid bars (hybrid fiber reinforced polymer) was introduced to increase the rigidity of FRP reinforcement, which was a basic drawback of the FRP bars used so far. Compared to the BFRP (basalt fiber reinforced polymer) bars, modification has been introduced in HFRP bars consisting of swapping basalt fibers with carbon fibers. One of the most important mechanical properties of FRP bars is compressive strength, which determines the scope of reinforcement in compressed reinforced concrete elements (e.g., column). The compression properties of FRP bars are currently ignored in the standards (ACI, CSA). The article presents compression properties for HFRP bars based on the developed compression test method. Thirty HFRP bars were tested for comparison with previously tested BFRP bars. All bars had a nominal diameter of 8 mm and their nonanchored (free) length varied from 50 to 220 mm. Test results showed that the ultimate compressive strength of nonbuckled HFRP bars as a result of axial compression is about 46% of the ultimate strength. In addition, the modulus of elasticity under compression does not change significantly compared to the modulus of elasticity under tension. A linear correlation of buckling load strength was proposed depending on the free length of HFRP bars.

Thermal effect on fiber reinforced polymer reinforced concrete slabs

2008 ◽  
Vol 35 (3) ◽  
pp. 312-320 ◽  
Author(s):  
A. Zaidi ◽  
R. Masmoudi
Keyword(s):  
Thermal Effect ◽  
Concrete Cover ◽  
Fiber Reinforced Polymer ◽  
Concrete Slabs ◽  
Fiber Reinforced ◽  
Reinforced Concrete Slabs ◽  
Reinforced Polymer ◽  
Frp Bar ◽  
Frp Bars ◽  
Concrete Interface

The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar – concrete interface, which induces tensile stresses within the concrete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insufficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from –30 to +80 °C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 °C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 °C. Also, the first cracks appear in concrete at the FRP bar – concrete interface at temperatures around +40 °C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.

Behavior and modeling of post-heated circular concrete specimens repaired with fiber-reinforced polymer composites

2021 ◽  
pp. 136943322110585
Author(s):  
Seyed Mehrdad Elhamnike ◽  
Rasoul Abbaszadeh ◽  
Vahid Razavinasab ◽  
Hadi Ziaadiny
Keyword(s):  
Strain Curve ◽  
Concrete Columns ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Concrete Members ◽  
Frp Composites ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites

Exposure of buildings to fire is one of the unexpected events during the life of the structure. The heat from the fire can reduce the strength of structural members, and these damaged members need to be strengthened. Repair and strengthening of concrete members by fiber-reinforced polymer (FRP) composites has been one of the most popular methods in recent years and can be used in fire-damaged concrete members. In this paper, in order to provide further data and information about the behavior of post-heated circular concrete columns confined with FRP composites, 30 cylindrical concrete specimens were prepared and subjected under four exposure temperatures of 300, 500, 700, and 900. Then, specimens were repaired by carbon fiber reinforced polymer composites and tested under axial compression. Results indicate that heating causes the color change, cracks, and weight loss of concrete. Also, with the increase of heating temperature, the shape of stress–strain curve of FRP-retrofitted specimens will change. Therefore, the main parts of the stress–strain curve such as ultimate stress and strain and the elastic modulus will change. Thus, a new stress–strain model is proposed for post-heated circular concrete columns confined by FRP composites. Results indicate that the proposed model is in a good agreement with the experimental data.

Utilizing alkali-activated materials as ordinary Portland cement replacement to study the bond performance of fiber-reinforced polymer bars in seawater sea-sand concrete

2022 ◽  
pp. 136943322110651
Author(s):  
Ruiming Cao ◽  
Bai Zhang ◽  
Luming Wang ◽  
Jianming Ding ◽  
Xianhua Chen
Keyword(s):  
Tensile Strength ◽  
Bond Strength ◽  
Ordinary Portland Cement ◽  
Concrete Strength ◽  
Fiber Reinforced Polymer ◽  
Bond Performance ◽  
Reinforced Polymer ◽  
Sea Sand ◽  
Frp Bars ◽  
Alkali Activated

Alkali-activated materials (AAMs) are considered an eco-friendly alternative to ordinary Portland cement (OPC) for mitigating greenhouse-gas emissions and enabling efficient waste recycling. In this paper, an innovative seawater sea-sand concrete (SWSSC), that is, seawater sea-sand alkali-activated concrete (SWSSAAC), was developed using AAMs instead of OPC to explore the application of marine resources and to improve the durability of conventional SWSSC structures. Then, three types of fiber-reinforced polymer (FRP) bars, that is, basalt-FRP, glass-FRP, and carbon-FRP bars, were selected to investigate their bond behavior with SWSSAAC at different alkaline dosages (3%, 4%, and 6% Na2O contents). The experimental results manifested that the utilization of the alkali-activated binders can increase the splitting tensile strength ( ft) of the concrete due to the denser microstructures of AAMs than OPC pastes. This improved characteristic was helpful in enhancing the bond performance of FRP bars, especially the slope of bond-slip curves in the ascending section (i.e., bond stiffness). Approximately three times enhancement in terms of the initial bond rigidity was achieved with SWSSAAC compared to SWSSC at the same concrete strength. Furthermore, compared with the BFRP and GFRP bars, the specimens reinforced with the CFRP bars experienced higher bond strength and bond rigidity due to their relatively high tensile strength and elastic modulus. Additionally, significant improvements in initial bond stiffness and bond strength were also observed as the alkaline contents (i.e., concrete strength) of the SWSSAAC were aggrandized, demonstrating the integration of the FRP bars and SWSSAAC is achievable, which contributes to an innovative channel for the development of SWSSC pavements or structures.

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