Reinforcement Bars Research Articles

A Case Study on Using the Concrete Cover Block in Steel Reinforcement Bar: Ghorahi Dang, Nepal

Cover block is one of the basic component on building structure like slab, column, beam, foundation. It is a multi- functionary engineering material. In maximum construction sites, bricks, stones, steel bars are used instead of cover block. This brings a lots of depraved consequences on building structures like lack of well spacing between surface and reinforcement bars, unbalance position of steel bars, reduce the lifespan of building and corrosion. Here, the main function of cover block is to reinforce the building structure by avoiding the corrosion on steel bar or avoiding the moisture with the steel bar, providing the resistive property, distributing an uniform load and managing space. In this way, the cover block is attached in a reinforcement bar in order to reinforce a building structure. When cover block was applied in a building structure, it made a building more durable as well as more attractive by maintaining the shape. This observation suggests that the use of cover block can contribute in strengthening a building structure and maintaining a position and space of a reinforcement bars as well as a structure. Key Words: Concrete cover block, Reinforcement bar, Potential failure of structure, Space maintaining, Corrosion activity.

Effects of Different Inhibitors on the Corrosion Mitigation of Steel Rebar Immersed in NaCl-Contaminated Concrete Pore Solution

The corrosion of steel rebar embedded in concrete under marine conditions is a major global concern. Therefore, it needs a proper corrosion mitigation method. Various types of corrosion inhibitors are used to mitigate the corrosion of steel rebar in chloride-contaminated concrete; however, selecting the appropriate inhibitor and determining its optimal concentration remains a concern. Therefore, in the present study, three types of inhibitors—calcium nitrite (CN: Ca(NO2)2), N,N′-dimethyl ethanol amine (DMEA: (CH3)2NCH2CH2OH), and L-arginine (LA: C6H14N4O2) in three different concentrations, i.e., 0.3, 0.6 and 1.2 M—were compared with a control (without inhibitor, i.e., blank) sample to determine the optimum concentration of the inhibitor for corrosion resistance performance evaluation of reinforcement bars immersed in 0.3 M NaCl-contaminated concrete pore (NCCP) solution for various durations. The corrosion resistance properties were assessed using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) with immersion duration, and potentiodynamic polarization (PDP) after 168 h of exposure. The results showed that the CN inhibitor performed exceptionally well (corrosion inhibition efficiency greater than 97%) in terms of corrosion resistance. However, due to its hazardous nature and its ban in the U.S. and European Union, CN cannot be used in construction. In comparison, while DMEA showed some effectiveness, LA performed better and is also eco-friendly. The corrosion resistance efficiency of samples containing 0.6 M LA remains above 97% even after 168 h of immersion in the NCCP solution. This efficiency is consistent throughout the entire immersion period, from 1 h to 168 h. Therefore, it is recommended that LA be used as a corrosion inhibitor for steel reinforcement bars instead of CN, particularly in chloride-contaminated concrete, as it is both effective and safer than CN.

Effectiveness of shear key on torsional resistance of precast beam: An experimental and numerical investigations

The present study evaluates the behaviour of wet precast beam-to-beam connection under pure torsion through experimental and numerical studies. A wet connection is provided at the central region of the precast beam. Two precast beam elements are connected by welding the overlapped portion of reinforcement bars projecting from each beam element. Furthermore, inward and outward shear keys are provided within the connection region to examine the efficacy of shear keys on the torsional resistance of the precast beam. Also, the behaviour of precast beams with and without shear keys is compared with monolithic beams. Experiments are conducted using a loading frame, designed and fabricated to create a pure torsion effect on the beam specimen under the application of monotonic vertical load. The response of test specimens is evaluated through various parameters such as torque and corresponding twist at different phases of loading, torsional ductility index, crack formation and failure propagation. Experimental studies show that shear keys provided within the connection region effectively contribute to force transfer and enhance torsional resistance of the precast beam by 16 %−24 % as compared to monolithic beam and precast beam without the shear key. A numerical analysis of the precast beam is carried out, and the behaviour of test specimens obtained from experimental studies is compared. The damage pattern and torque-twist behaviour obtained from numerical studies adequately simulate the response of test specimens observed during the experimental study.

Progress in Corrosion and Protection Research in Offshore Petroleum Engineering

This paper summarizes the latest research progress on the corrosion of concrete structures in marine engineering and its protection technology. The article firstly emphasizes the influence of seawater on the performance of concrete engineering, and then discusses the application of composite corrosion inhibitors in the marine environment. The composite corrosion inhibitor significantly reduces the corrosion rate by simultaneously inhibiting the anodic and cathodic reactions and forming a protective hydrophobic film on the metal surface. The article describes in detail the classification of corrosion inhibitors, including adsorption or film-forming inhibitors with polar hydrophobic groups such as N, S, and -OH, as well as migratory corrosion inhibitors (MCIs) that diffuse through the pores of the concrete to the surface of the reinforcement bar to form a protective film. The article also discusses the performance evaluation criteria of corrosion inhibitors, including the electrochemical performance of saltwater impregnation, the performance of dry-wet cold-heat cycles, and the performance of resistance to Cl- penetration, etc., and lists the relevant national standards and test methods. Through a comprehensive analysis of relevant literature at home and abroad in recent years, the article points out that composite corrosion inhibitors show great potential in improving the durability of marine concrete structures, but the long-term stability and compatibility with different concrete types still need to be further studied. Future research should focus on developing more efficient and environmentally friendly corrosion inhibitors and expanding their application in marine engineering to meet the increasingly severe challenges of marine corrosion. At the same time, a comprehensive evaluation of the longevity, economy and environmental friendliness of corrosion inhibitors is also an important direction for future research.

Contribution to the Study of the Chemical and Microstructural Quality of Reinforcing Bars in DR. Congo “Case of the City of Lubumbashi”

This research highlights the contribution to the study of the microstructural quality of reinforcing bars on the Lubumbashi market including bars imported from South Africa (FA), Zambia (FZ) and those produced locally ( FC) by the only steel industry, in the former province of Katanga, the iron processing company SOTRAFER, in acronym. The samples of the locally produced reinforcement bars (FC) were collected at SOTRAFER at the end of production, while the samples of the FA and FZ reinforcement bars were taken randomly on the Lushois market in a hardware store specializing in sales to avoid errors.Microstructural analysis of all bars revealed a similar microstructure consisting of a ferrite (light areas) and pearlite (dark areas) matrix and a ferrito-pearlitic structure. This microstructure, as predicted by the Fe-C equilibrium diagram, could be justified by the carbon content (lower than the eutectoid point content); the results prove that all bars are hypoeutectoid steels (%C ≤ 0.77). They can also be assimilated to the category of mild steels (0.1 ≤ %C ≤ 0.25). This also shows that all the bars have not undergone a particular heat treatment and have been cooled very slowly in order to allow the diffusion of atoms and reach equilibrium conditions. The results obtained from the variance analyses of different materials of dimensions of 10, 12 and 16 mm revealed that at the level of chemical and mechanical analyses, there was no significant difference on all the parameters studied and that all the reinforcement bars could perfectly be used in construction. Finally, the survey reveals that FA is reputed to be of better quality among consumers, for several reasons including the psychological one although its price is lower than that produced locally.

Flexural behaviour of BFRP grid/bar reinforced UHPC beams and slabs

This study investigates the integration of Basalt Fiber Reinforced Polymer (BFRP) and Ultra-High Performance Concrete (UHPC), which exhibit significant potential for a durable and sustainable solution in marine and offshore infrastructure. An experimental program of BFRP grid/bar-reinforced UHPC beams and slabs subjected to four-point bending is presented. A total of nine beams and ten slabs were prepared and tested to investigate the effect of BFRP reinforcement ratio (0 %–3.33 %), type of reinforcement (grid and bar), and steel fiber content of UHPC (0 %, 1 %, 2 % and 3 %). The results revealed that the inclusion of BFRP reinforcement, even at a small reinforcement ratio, is feasible to enhance structural ductility due to the large rupture strain and superior strength characteristics of BFRP material. Moreover, the steel fibers played a crucial role in preventing shear failures of UHPC and creep failures of BFRP reinforcement. Within a range of 0–2 %, the steel fiber content not only benefited the load-resistance and deformation capacity but also effectively improved the cracking load. However, high fiber content (3 %) had a minimal contribution to load-bearing capacity and negatively affected ductility. A theoretical model based on the deflection method was employed to forecast the general behaviour of the flexural members. Comparisons between experimental results and numerical predictions confirm its accuracy.

Numerical Modeling of Distributed Macro-Synthetic Fiber and Deformed Bar Reinforcement to Resist Shear

Macro-synthetic fibers are increasingly used in concrete as secondary reinforcement to control temperature and shrinkage cracks, improving durability by limiting crack widths. However, their impact on the shear strength of structural elements remains underexplored, particularly when used in combination with traditional steel reinforcement. To address this knowledge gap, this study developed and calibrated a non-linear numerical model to simulate the shear response of macro-synthetic fiber-reinforced concrete (PFRC) elements, using finite element software VecTor2. The model was calibrated with experimental data from PFRC panels subjected to pure shear loading, incorporating a custom concrete tension-softening model to capture the contribution of fibers. Validation against a broad range of PFRC beam experiments from the literature demonstrated the model’s accuracy, achieving an average predicted-to-experimental shear strength ratio of 0.99 (COV = 5.5%). Additionally, the model successfully replicated key response characteristics such as deformation patterns, crack propagation, and residual strength. The proposed modeling approach provides valuable insights into the interaction between fiber volume and transverse reinforcement. It also serves as a powerful tool for future numerical studies, addressing the existing data gap on PFRC behavior and exploring the synergistic effects of macro-synthetic fibers and steel reinforcement on shear strength.

Short‐length mechanical bond anchorage for reinforcement bars made of FRP: Experimental and numerical investigations

Short‐length mechanical bond anchorage for reinforcement bars made of <scp>FRP</scp>: Experimental and numerical investigations

Ginger powder as sustainable and eco-friendly corrosion inhibitor for the protection of steel reinforcement bars

In the present studies, ginger powder has been used as an eco-friendly admixture for the cement mortar. Different amounts i.e. 0 wt% (M1), 0.10 wt% (M2), 0.25 wt% (M3) and 0.50 wt% (M4) ginger powder was mixed in the cement mortar (M1) and assessed the durability. The ginger powder with 0.50 wt% (M4) improves the compressive strength by 17 % owing to the water reducing capability, which enhance the hydration reaction and fill the pore matrix of the cement mortar. The active ingredient of ginger powder i.e. shogaol adsorbs on the steel rebar surface through leaching mechanism by interaction of oxygen (O) and п-electrons with iron (Fe) and provide corrosion protection at longer duration of continuous immersion in 3.5 wt% NaCl solution. Following 173 d in a 3.5 wt% NaCl solution, the M4 sample exhibits 82.10 % corrosion inhibition efficiency. Therefore, it is suggested that ginger powder could be a potential eco-friendly admixture to be used in construction industries to get high durability performance in the coastal areas.

Carbonation of composites with recycled aggregate subjected to carbon dioxide sequestration process

In light of the growing issue of climate change, it is necessary to take actions aimed at reducing the emissions of carbon dioxide (CO2) into the atmosphere. CO2 sequestration, especially in the process of concrete production, can be a crucial step in combating this phenomenon. The study attempted to utilize recycled aggregate for CO2 sequestration and assess its effect on the carbonation depth of the mortar. The loss on ignition analysis of the aggregate showed a 2.9% CO2 absorption. Mortar with carbonated aggregate exhibited the highest degree and depth of carbonation among the tested specimens, albeit eight times lower than the depth typically containing reinforcement bars

Bond Strength and Development Length Model for Corroded Reinforcing Bars

Bond Strength and Development Length Model for Corroded Reinforcing Bars

Optimization of Shear Resistance in Horizontal Joints of Prefabricated Shear Walls through Post-Cast Epoxy Resin Concrete Applications

The horizontal joint is a critical component of the prefabricated shear wall structure, responsible for supporting both horizontal shear forces and vertical loads along with the wall, thereby influencing the overall structural performance. This study employs direct shear testing and finite element analysis to investigate the horizontal joint in walls with ring reinforcement. It examines the impact of various factors on joint shear performance, including the type of joint material, joint configuration, buckling length of ring reinforcement, strength of precast concrete, reinforcement ratio of ring reinforcement and dowel bars, and the effect of horizontal binding force. The findings indicate that the shear bearing capacity and stiffness of joints incorporating post-cast epoxy resin concrete and keyways are comparable or superior to those of integrally cast specimens. A larger buckling length in ring reinforcement may reduce shear strength, suggesting an optimal buckling length at approximately one-third of the joint width. As the strength of precast concrete increases, ductility decreases while bearing capacity increases, initially at an increasing rate that subsequently declines. Optimal results are achieved when the strength of precast concrete closely matches that of the post-cast epoxy concrete. Enhancing the reinforcement ratio of ring reinforcement improves shear capacity, but excessively high ratios significantly reduce ductility. It is recommended that the diameter of ring reinforcement be maintained between 10 mm and 12 mm, with a reinforcement ratio between 0.79% and 1.13%. Increasing horizontal restraint enhances stiffness and shear capacity but reduces ductility; thus, the axial compression ratio should not exceed 0.5.

Bond behavior between bundled steel-FRP composite bars and grouted corrugated duct

The utilization of steel-fiber reinforced polymer (FRP) composite bars (SFCBs) reinforcement in precast concrete structures offers numerous benefits, including controllable post-yield stiffness and reduced residual displacement. Employing bundled reinforcement can improve construction efficiency. This study presents direct pull-out tests conducted on SFCBs embedded in grouted corrugated ducts. The results show that bond strength decreases with both the number of bars in a bundle (nb) and the actual embedded length (la). The bond strength of single bar SF-1b-3d with 3d embedded length is 24.21 MPa, while that of 2-bar bundled SF-2b-3d and 3-bar bundled SF-3b-3d is 17.41 MPa and 12.61 MPa, respectively. Additionally, the error in predicting the bond strength between bundled SFCBs and grouted corrugated duct using the equivalent diameter method is found to be less than 8.4%. Utilizing the mBPE constitutive model, an analytical hardening-slip model with a linear slip field assumption accurately predicts the full-range behavior, bond stress distribution, and SFCB's axial stress distribution. Furthermore, the effects of different parameters on yield slip sy, ultimate slip su, and critical anchorage length Ltr are investigated by considering different local bond-slip constitutive models (varying peak bond strength τm and its corresponding slip sm and ascending section coefficient (α) as variables. The yield slip sy varies from 0.1 mm to 1.3 mm, while the ultimate slip su can reach a maximum of 35.0 mm. Furthermore, the validity of existing models for evaluating the anchorage length of single SFCB and bundled SFCBs grouted in corrugated duct connections is discussed, and a formula to estimate the critical anchorage length of bundled SFCBs and grout considering the number of bars within one bundle (nb) is proposed.

Size Effects in Climatic Aging of Epoxy Basalt Fiber Reinforcement Bar.

The purpose of this study was to obtain information on the influence of the size factor on the climatic aging of circular fiber plastics produced by pultrusion. The kinetics of moisture transfer was obtained in humidification and drying modes at 60 °C in samples of epoxy basalt fiber reinforcement bars: after 28 months of exposure in the extremely cold climate of Yakutsk and 30 months of exposure in the moderately warm climate of Gelendzhik. It was shown that the 2D Langmuir model adequately describes the kinetics. The diffusion coefficients in the reinforcement direction for bars with diameters of 6, 8, 10, 16 and 20 mm turned out to be significantly higher than in the radial direction. To clarify the aging mechanism of the bars and the tensile, compressive and bending strength, the coefficient of linear thermal expansion and the glass transition temperature of the epoxy matrix of the bars with a diameter of 6, 8 and 10 mm after 51 months of exposure in Yakutsk and 54 months of exposure in Gelendzhik were measured. It was shown that after climatic exposure, the deformability of the bars decreased with increasing diameter of the bar; the glass transition temperature increased more significantly in the bar with a smaller diameter. In 6 mm diameter bars, the compressive and bending strength limits decreased by 10-25 % due to the plasticizing effect of moisture. With the same depth of moisture penetration into the volume of the samples, its effect on the strength of thin bars was significant, and for thick bars, it was insignificant. An increase in the glass transition temperature by 6 °C, associated with the additional curing of the polymer matrix, occurred in the surface layer of the epoxy basalt fiber reinforcement bars and was revealed in bars with a smaller diameter.

Flexural Behavior of Precast Rectangular Reinforced Concrete Beams with Intermediate Connection Filled with High-Performance Concrete

Precast rectangular reinforced concrete (PRRC) beams are joined on construction sites using concrete in situ to achieve the desired length. Limited research exists on the effect of intermediate connection shapes and the types of infilled concrete on the flexural performance of PRRC beams. This paper presents a comprehensive experimental and numerical investigation into the performance of PRRC beams with various intermediate connection geometries and infilled materials under flexural loading. The study examines rectangular, triangular, and semi-circular intermediate connections, along with the performance of beams infilled with normal concrete (NC), engineered cementitious composites (ECC), ultra-high-performance ECC (UHPECC), and rubberized ECC (RECC). The experimental results indicate that the rectangular intermediate connection exhibits superior performance in terms of strength and energy absorption compared to the triangular and semi-circular shapes. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC for any shape of intermediate connection. Moreover, beams with rectangular connections and UHPECC infill exhibited the most significant increase in energy absorption and ultimate load compared to the beams with ECC and RECC. The ultimate load of the beams with UHPECC and tensile reinforcement bar diameters of 10 mm and 12 mm increased by 13% and 29%, respectively, compared to the control beam. The energy absorption of the beams with tensile reinforcement bar diameters of 10 and 12 mm was found to be 75% and 184% higher, respectively, than the control beam. In addition, an increase in tensile bar diameter was found to enhance both the energy absorption and the ultimate load capacity of the beams, regardless of the type of infill concrete. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC. In particular, beams with rectangular connections and UHPECC infill exhibited an increase in energy absorption and ultimate load of up to 184% and 29%, respectively. UHPC was calculated to be as high as 184%, and 29%, respectively, compared to the control beams. In addition, an increase in tensile bar diameter was found to enhance both energy absorption and ultimate load capacity. Finite element modeling (FEM) was developed and validated against the experimental results to ensure accuracy. A parametric study was conducted to study the effects of various concrete types in triangular and semi-circular connections, as well as the influence of intermediate connection length on semi-circular connections under flexural loads. The findings reveal that increasing the length of intermediate connections increases the ultimate load of the beams.

Structural performance of hybrid reinforced concrete beams containing polyvinyl alcohol fibers under thermal loads

This study focused on the efficiency of concrete beams containing polyvinyl alcohol fibers (PVA) under thermal loads. The eighteen concrete beams were reinforced with hybrid bars or a combination of GFRP bars and steel reinforcement bars (hybrid scheme). The main experimental variables were the level of temperature (25o, 300o, and 600o C), PVA fiber volume (0 %, 0.50 %, and 1.0 %), and the flexural reinforcement bars. The experimental test results are discussed in terms of the first crack load, flexural capacity, and load-deflection curves. Moreover, the initial and post-crack stiffness, ductility factor, and failure modes are discussed. The test results demonstrated a significant increase in the capacity of PVA concrete beams reinforced with hybrid reinforcement bars. At a temperature of 300o C, the inclusion of 0.50 % and 1.0 % PVA ratios improved the flexural capacities by 11 % and 24 %, respectively. Furthermore, the addition of PVA fibers enhanced the toughness by 34 % and 67 %, respectively, when compared to normal concrete beams. The results also demonstrate that using PVA fibers prevents the spalling of concrete beams after exposure to elevated temperatures. At 600 °C, beams containing 0.50 % and 1.0 % PVA fibers exhibited flexural capacities that were 9 % and 6 % higher, respectively, compared to normal concrete beams. Additionally, the inclusion of PVA fibers increased the toughness by 27 % and 21 % for the respective fiber ratios. Finally, a nonlinear finite element analysis (NLFEA) simulation was performed to verify the experimental test results and supplement experiments by predicting the results that are difficult to accomplish through experiments. With an average ratio of 1.02 between experimental and NLFEA ultimate capacity, the numerical results were an exact match of the patterns observed in the experimental results.

Performance evaluation of indented macro synthetic polypropylene fibers in high strength self-compacting concrete (SCC)

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

Effect of corrosion on bond between reinforcement and concrete-an experimental study

The presence of cracks in concrete structures can lead to corrosion as it exposes the steel reinforcement to environmental factors. When moisture and oxygen reach the steel, corrosion weakens the bond between the steel and the surrounding concrete. This weakening can reduce the load-carrying capacity and, in severe cases, lead to failure. Understanding the relationship between corrosion and bond strength is vital for reinforced concrete structures. This paper investigates the impact of corrosion on bond strength in reinforced concrete structures by examining the bond performance of concrete with both corroded and uncorroded reinforcement bars. The study considers concrete grades M20, M25, and M30, as well as corrosion levels varying from 0 to 20% in intervals of 5%. To conduct the study, cylindrical samples with different levels of corrosion were created using the corrosion acceleration process with the impressed current technique. Pull-out tests were then carried out to determine the bond-slip relationship and the degradation of bond strength due to corrosion. The test results show that lower-grade concrete (M20) experiences a significant decrease in bond strength compared to higher grades (M25 and M30), with M20 showing a 30.7% reduction and M25 showing a 25.8% reduction in bond strength relative to M30 in controlled specimens. The bond stress-slip relationship reveals a non-linear response, with reduced bond stress and slips for all grades of concrete as corrosion levels increase. Additionally, the reduction in bar diameter due to corrosion ranged from 11.3 to 11.6 mm at 5% corrosion and from 9.4 to 9.7 mm at 20% corrosion, significantly impacting the load-carrying capacity of the reinforced concrete structures. These findings underscore the importance of considering concrete grade and corrosion levels when assessing and maintaining bond performance in reinforced concrete structures.

Shear repairing of reinforced concrete beams exposed to high temperature using basalt fiber reinforcing bars and CFRP ropes and strips

In this research, the shear behavior of reinforced concrete (RC) beams subjected to high temperatures and then repaired using Basalt Fiber Reinforcing (BFRP) bars and Carbon Fiber Reinforced Polymer (CFRP) ropes and strips was investigated experimentally. Eleven reinforced concrete beams with shear deficiency were cast with dimensions 200mmx300mmx1800mm in width, depth, and span length, respectively. Then, after 28 days, ten beams were heated in an electric furnace for three hours at a temperature of 650 °C. Later, nine of the heated beams were repaired using near surface mounted technique (NSM) with different configurations of BFRP bars and CFRP ropes and strips, and one beam was left unrepaired to serve as a control heated sample. The behavior of the beams was evaluated under two-point loading. The experimental results showed that using NSM CFRP or BFRP efficiently enhances the shear capacity of heat damaged beams. Using NSM rope increased the ultimate loads by 40 % to 95 % compared to control heat beams. The highest improvement in maximum load capacity was achieved by using an inclined rope positioned at 150 mm. While, using BFRP bar increased the maximum load by 37 % to 63 % compared to control heat beams depending on the configuration and spacing between bars. Also, it has been found that the overall effectiveness of CFRP rope in increasing the shear capacity is 32 % higher than that of the BFRP bars.

Shear strength and ductility of novel steel fibre-reinforced concrete dowel connections for composite beams

In this paper, a novel steel fibre-reinforced concrete (SFRC) dowel connection without traditional steel bar reinforcement is proposed for steel-concrete composite beams. Push-out tests on thirty-six specimens were conducted to investigate the shear strength and ductility of SFRC dowel connections with varying dowel sizes, concrete densities, fibre content and type. Even without the presence of reinforcing bars, the SFRC dowels were able to resist substantial loads and maintained a ductile load-slip behaviour. The shear strength of SFRC dowels increased with an increase in the fibre content, dowel size, and concrete density. Further, dowels with higher steel fibres content exhibited enhanced ductility, displaying a near elastic-plastic load-slip behaviour, with an ability to resist up to 80 % of the ultimate load even at 6 mm slip. A unique analytical model to predict the ultimate load and the load-slip curve is proposed in this study. The model was able to predict the ultimate load to within 6 % of test results, on average, while the mean load at 6 mm slip was predicted to within 3 % of the test results, with standard deviation of 17 % and 13 % respectively. The general shape of the load-slip curve was also well predicted. The study also proposes simplified equations, which predicted the shear strength of SFRC dowels to within 2 % of the test results with a standard deviation of 13 %.