Types Of Bars Research Articles

Experimental investigation on bond properties of nano-Al2O3 and hydroxypropyl methyl cellulose (HPMC) modified coated steel bar embedded in concrete

In this work, cementitious coatings incorporate nano-Al2O3 (NA) and HPMC were developed applying to the surface of steel bars to enhance bond behavior. A total of 81 pull-out specimens were prepared to evaluated bond properties of different coated steel bars embedded in ordinary performance concrete (OPC), high performance concrete (HPC) and ultra-high-performance concrete (UHPC). The mechanical properties of the cement-based coatings have also been examined. Test results show that flexural and compressive strengths of coating paste exhibited initially increasing and followed by decreasing as NA content increase. Synergistic effect of NA and HPMC results in cement-based coating exhibiting superior mechanical properties. Besides, coating microscopic morphology characterized by scanning electron microscope (SEM) technique revealed that fewer coating defects with NA and HPMC compounding. More importantly, the highest bond strength between coated steel bar and different types concretes was found at 1.0 % NA content in the coatings. Synergistic effect of 1.0 % NA and 0.12 % HPMC improved bond strength of coated steel bar embedded in OPC, HPC and UHPC. It can be obtained from bond-slip curve that, regardless of the HPMC addition to coatings, coated steel bar with 1.0 % NA content shows higher bond stiffness. With both NA and HPMC added, bond stiffness, bond toughness and bond ductility of coated steel bar are superior to those of the coating with NA alone. Moreover, as concrete strength increases, the bond strength, bond stiffness and bond toughness of coated steel bar also increase, respectively.

The efficacy of home-made soap from used cooking oil and pineapple waste for eco-friendly household product

As the human population increases globally, the waste production rate from various types of waste such as used cooking oil and fruit waste also increases. The development of this dish soap bar helps in spreading awareness for people not to discharge used cooking oil and fruit waste into the drainage system. Instead, one can opt to transform these waste products into soap. This study aims to develop a dish soap bar using used cooking oil and pineapple waste. The efficacy of the soap was evaluated following the eco-friendly product criteria. In this study, eight types of dish soap bars were developed with two variables namely concentration and type of pineapple parts. The whole parts of pineapple waste were prepared with 100%, 75%, 50%, and 0% concentration. Different parts with 100% concentrations were developed from peel, core, stem, and crown parts. The dish soap bar samples were evaluated for their efficacy based on pH value, moisture content, and foam height. It has been compared among samples, control, and commercial soaps. The commercial brand, Labour, has the highest foam height (6.61 cm) and pH value (10.53) and the sample core (Conc. 100%) showed the highest moisture content (12.19%). The significant value among samples, control, and commercial soap for each pH value, foam height, and moisture content was determined by using SPSS21 software. The pH value and foam height of the samples were highly significant (F1,32 = 16.275, p <0.001). The moisture content also showed a significant difference (F1,32 = 2.889, p <0.05). The Dunnett multiple methods were used to determine the most samples that were closed to control. Five samples were close to the control. Brine shrimp test the toxicity of the sample. The average survival rate of brine shrimp for the whole part (Conc. 50%) dish soap bar sample was 36.7%. The sensory evaluation proceeded to look at the overall acceptance of the sample among 50 respondents and from the evaluation, 36 respondents (72%) were very satisfied with the final product sample whole part (Conc. 50%).

Bond behavior between the deformed steel bar and different types of cementitious grout under reversed cyclic loading

To systematically investigate the bond behavior of deformed steel bars in cementitious grout, direct pullout tests were conducted on 15 sets of specimens by considering five types of cementitious matrixes and three different loading schemes. The failure modes, bond stress-slip curves, as well as the bond degradation and cumulative energy dissipation of specimens under reversed cyclic loading, were compared and analyzed. Results indicate that splitting pull-out or pull-out failure modes were observed, and pull-out failure was the most common failure mode of the specimen (accounting for 91 %) due to the installation of stirrups and the sufficiently short anchorage length. Meanwhile, regardless of the loading scheme, the general relationship between the magnitude of maximum bond stress of specimens composed of different cementitious materials was shown as C60＞CGM-270＞CGM-300＞CGM-340＞CGM-380, while there was no consistent pattern in relative slippage. Moreover, the relationship between the degradation of the maximum bond stress and stiffness of each specimen under reversed cyclic loading was shown as CGM-380 >CGM-340 ≈CGM-300 >CGM-270 >C60. The degradation mainly occurs in the first two cycles, and then gradually stabilizes. Furthermore, the cumulative energy dissipation relationship of specimens with different materials was shown as C60 >CGM-270 >CGM-300 >CGM-340 >CGM-380 under the reversed cyclic loading. The above investigations could provide theoretical support for the evaluation of ductility and energy dissipation of concrete members strengthened with cementitious grout under earthquake actions.

The Variation in Boulder Bars Triggered by the 2018 Sedongpu Natural Dam Failure in the Yarlung Tsangpo River

Natural dams are formed most often in narrow, steep valleys in high mountains. The outburst floods triggered by natural dam failures result in the topography and landforms successively being altered. Boulder bars are common natural structures that are selected here to quantitatively evaluate the impact of outburst floods on the topographical and landform variations in downstream channels. In this study, we selected the Sedongpu natural dam on the Yarlung Tsangpo River formed as a result of a landslide in 2018 as an example, and studied the geomorphological changes in a river reach located 173 km downstream of the Sedongpu natural dam. The sizes and shapes of the boulder bars in this area were statistically analyzed. The results show that there are three shape types of boulder bars in this area, i.e., sickle, bamboo leaf and oval. Furthermore, it found that the relationship between the lengths and widths of boulder bars is similar before and after outburst floods, as is the relationship between perimeters and lengths of boulder bars, which means these relationships are not affected by outburst floods. And the perimeters of boulder bars are almost twice their lengths. In addition, the relationship between the areas and lengths of boulder bars follows a power function. The most important finding is that the riverine morphological features conserved self-similarity due the influence of the outburst flood erosion triggered by a natural dam failure. This finding adds to the previous observations since dam failures introduce sudden and dominating impacts on river systems.

Retrofitting performance of precast UHPC jackets and NSM GFRP bars in pre-damaged RC columns with deficient lap splices

Fiber-reinforced polymer (FRP) jackets and the near surface-mounted (NSM) technique have been widely used to improve the seismic performance of intact reinforced concrete (RC) columns with deficient lap splices. For damaged lap-spliced RC columns, use of ultra-high-performance concrete (UHPC) jackets is more powerful in eliminating the bond splitting failure and recovering the stiffness than FRP jackets. This study proposed an L-shape precast steel-reinforced UHPC (PR-UHPC) jacket to improve the retrofit performance of conventional cast-in-place (CIP) and precast UHPC jackets. Further, PR-UHPC jackets were combined with NSM GFRP bars to develop an innovative method. Cyclic loading tests were performed on three three-fourths scaled deficient lap-spliced RC columns. One intact column was directly retrofitted with PR-UHPC jackets, while the other two were first damaged and then retrofitted with PR-UHPC jackets and the combination of PR-UHPC jackets and NSM GFRP bars, respectively. To investigate the effects of UHPC details and NSM bar types, a previous study on lap-spliced RC columns retrofitted with CIP plain UHPC jackets and NSM steel bars was incorporated. The test results indicate that the retrofitted columns failed with rebar fracture, and plastic hinge shifting was prevented. The peak load, effective yield stiffness, and ultimate drift ratio of the retrofitted columns were 29∼50 %, 37∼39 %, and 126∼165 % higher than those of the unretrofitted columns, respectively. NSM GFRP bars outperformed steel bars in terms of residual drift ratio control. The numerical model well predicted the cyclic behavior by addressing the pre-damage effect and the actual confinement of PR-UHPC jackets. The parametric study revealed that the increase of PR-UHPC jacket width effectively improved the strength and stiffness, while the pre-damage degree had a minor effect. The recommended UHPC jacket height for the present columns was 2.5 times the plastic hinge length. Finally, a design method was developed for the UHPC jacket width.

Experimental investigation on the tension lap splices used in the joints of precast RC foundation piles

AbstractThe joints between precast reinforced concrete pile segments in deep foundations are typically mechanically lockable. They include anchor bars embedded inside the ends of each segment, forming lap splices with the main bars. Because of their particular technology, these lap splices are somewhat different from traditional lap splices, as shown in the first part of this paper, where the impact of their specific characteristics on the tensile behavior of the joints is discussed. The experimental section presents the results of 19 tensile tests on these lap splices and compares them with established theoretical models. The roles of various parameters (lap length, type and amount of confining reinforcement, type of anchor bars, and concrete cover thickness) are investigated. One of the major findings indicates a significantly lower lap capacity when using plain‐bar spirals compared to closed‐ribbed stirrups. Additionally, at low stress levels, the models tend to be unconservative. Building on this insight, a modified model is proposed for lap splices provided with plain‐bar spirals.

Bond performance and constitutive model of steel bar in G-UHPC under cyclic loading

The increasing embrace of the low-carbon and environmentally sustainable construction approach has opened exciting opportunities for using environmentally friendly geopolymer based ultra-high-performance concrete (G-UHPC) in engineering structures, drawing significant attention to its performance. Seismic performance is a crucial factor in structural design, and it is greatly affected by the bond behavior between steel bar and concrete. As a result, a thorough understanding of the bond behavior of steel bars to G-UHPC provides essentially theoretical support for the structural design and nonlinear finite element analysis of G-UHPC structures, which is vital for their widespread implementation in earthquake engineering. This study tested 54 specimens from 18 groups to examine the bond performance of G-UHPC and steel bars under cyclic loading. The influence of concrete and steel bar types, protective layer thickness, bond length, and steel fiber on critical bond performance indicators were evaluated, and the bond stress-slip hysteretic and skeleton curves were analyzed. Subsequently, based on the experimental data, a constitutive model was proposed to predict the bond stress-slip relationship of steel bars and G-UHPC under cyclic loading. The results indicated that the steel bars exhibited superior bond performance with G-UHPC as compared to NSC. The bond and residual strength between steel rebars and G-UHPC was approximately 1.73 times and 3 times greater, respectively, in comparison with that between NSC and steel rebars. Increasing the strength of steel bars only resulted in a limited 2 % improvement in bond strength. The steel bar diameter, protective layer thickness, bond length, and the dosage and length of steel fibers in G-UHPC significantly influenced the bond performance. The addition of irregular-shaped steel fibers to G-UHPC has demonstrated potential in improving energy consumption, with the most remarkable enhancement observed for the inclusion of twisted steel fibers. Specifically, the incorporation of twisted steel fibers signally enhanced the energy consumption to approximately 1.3 times the energy dissipation as compared to straight steel fibers with the same dosage and aspect ratio. In addition, the accuracy of the proposed constitutive model has been validated.

Effects of using different riveting tools on the vibration exposure and muscle fatigue of riveters and buckers

Riveters and Buckers in the aircraft manufacturing industry are exposed to high vibration levels, often exceeding the Daily Exposure Limit Value (DELV) of 5 m/s2. Proper control of vibration exposure and muscle fatigue is crucial to minimize the risk of Work-related Musculoskeletal Disorders (WMSD). This study investigates the impact of different rivet guns, gun handle positions, and bucking bars on vibration exposure and muscle fatigue. Ten male participants, evenly divided between riveters and buckers, participated in the experiment. Throughout the investigation, various data, including acceleration, Electromyography (EMG), heart rate, grip strength, and perceived level of exertion, were collected simultaneously from the participants. The findings revealed that gun types 3 and 4 resulted in 43.27% lower vibration exposure than gun types 1 and 2, while combining a spring dampener and tungsten bucking bar yielded 24.46% less vibration than steel and tungsten. For both riveters and buckers, the horizontal gun handle position reduced vibration by 12.66% compared to the vertical handle position. Consequently, it is crucial to consider the type of gun, bucking bar, and handle position to mitigate vibration exposure and muscle fatigue among riveters and buckers in the aircraft manufacturing industry.

Seismic behaviors of steel-FRP composite bar-reinforced engineered cementitious composites columns under reversed cyclic loads

The combination of steel-FRP composite bar (SFCB) and engineered cementitious composites (ECC) in structures exposed to harsh conditions can offer benefits in mechanical performance and durability. In this study, the seismic behaviors of SFCB-reinforced ECC and concrete columns were investigated through reversed cyclic loading tests and the effects of matrix types, axial load ratios, and reinforcing bar types were discussed. The results showed that the SFCB-reinforced ECC columns experienced flexural failure characterized by SFCB fracture, whereas the SFCB-reinforced concrete columns failed owing to concrete crushing. The SFCB-reinforced ECC columns showed a 41.5 %− 116.3 % enhancement in deformation capacity and a 34.7 %− 65.2 % improvement in average energy dissipation coefficient compared with SFCB-reinforced concrete columns, which demonstrated that using ECC in SFCB-reinforced columns addressed issues of their low deformation and low energy dissipation capacity. In addition, the plastic hinge length of SFCB-reinforced columns increased substantially with the application of ECC, and the stiffness degeneration and residual deformation were reduced.

Anchorage and lap capacity of plain surface and square twisted bars in existing R.C. Structures: A comprehensive approach

AbstractAlthough plain round or square section reinforcement is no longer used in new construction, there are many older structures still in service built with such bars. In recognition of the need for guidance on the assessment of load‐carrying capacity of structures reinforced with such bars, design codes are now introducing or re‐introducing provisions to assess the capacity of laps and anchorages of such reinforcement. The authors have contributed to the introduction of design rules in the fib Model Code 2020. This paper describes the derivation of these provisions. Starting from the form of expression proposed earlier by the authors, the data from which these proposals are derived is specified and modifications in interpretation preparatory to a statistical analysis are outlined. A rigorous multivariate statistical procedure is then employed firstly to determine a mean strength expression for the capacity of anchorages and laps which is then validated against test data. Further statistical analysis is subsequently used to determine a design expression using the approach outlined in EN 1990, taking appropriate account scatter in test data. Finally, some comparisons are presented between the assessment expressions proposed and design provisions that were in place when these types of bars were in common use. Areas where earlier design provisions may be non‐conservative are identified.

Experimental study on the mechanical characteristics of a novel high-strength-and-high-toughness steel

To effectively control large deformation disasters, our team has developed a novel high-strength and high-toughness (HSHT) steel. This study aims to conduct a comparative analysis of the mechanical properties of HSHT steel and typical commercial steel under tension and impact. Testing was carried out using a universal testing machine and a self-developed drop-hammer-type longitudinal impact dynamic mechanical tester, with dynamic axial force sensors and infrared equipment utilized for monitoring. The results of the experiments are as follows: In the tensile test, HSHT steel exhibited superior performance in terms of tensile strength, elongation, and uniform deformation, particularly in radial deformation. The strength-ductility product of HSHT steel was more than two times that of typical commercial steel, indicating better energy-absorbing properties. Infrared data analysis showed that HSHT steel bars displayed uniform warming throughout their entire length. In the impact test, HSHT steel reinforcement demonstrated higher mechanical properties compared to commercial steel. Following failure, HSHT steel bars did not exhibit significant necking at the fracture site and showed a larger area of impact deformation. The axial forces experienced by the different steel bars were similar under various conditions. Data fitting analysis revealed an exponential relationship between the static tensile maximum strains of all bar types and the number of cyclic impacts. For HSHT steel bars, the number of impacts was also exponentially related to displacement, cyclic height, and energy absorbed prior to failure. Additionally, HSHT bars exhibited better uniform heating characteristics during cyclic impacts, with higher heating temperatures compared to typical commercial steels.

Study on the truss damage measurement based on Bayesian updating

Bayesian updating can integrate new observations in real time. This online updating property makes the Bayesian approach particularly suitable for dynamic monitoring of structural damage. In this paper, the node displacements are obtained by the finite element software OpenSees, assuming that the bars are damaged and the stiffness is reduced. Rejection Sampling method is used to determine the stiffness drop interval. During the sampling process, different load sizes, load locations, errors and types are selected to realize the updating of the stiffness of the top chord bar, bottom chord bar, vertical web bar, and diagonal web bar. A Pratt-type truss is used as an example, combined with displacement data. The proposed stiffness damage measurement method is demonstrated by updating the stiffness of four types of bars separately. The results shows that damage in structures can be accurately identified by Bayesian updating methods. This method not only pinpoints the location of the damage, but also quantifies the extent of the damage.

Structural efficiency of concrete beams reinforced with hybrid reinforcement bars under thermal loads

Nine reinforced concrete (RC) beams were experimentally tested to assess the effect of temperatures on the flexural performance of concrete beams with hybrid bars and GFRP-steel reinforcement. The study focused on the temperature levels (25 °C, 300 °C, and 600 °C), the reinforcement ratios, and the type of reinforcement bar. The test findings revealed a significant decline in the stiffness of beams with GFRP-steel reinforcement compared to hybrid reinforcement bar (HRB) beams. The stiffness decreased by 17 % and 31 % for 300 °C and 600 °C, respectively. Moreover, all beam specimens exhibited a flexural failure mode. Non-linear finite element analysis (NLFEA) results accurately reflected the trends observed in the experimental results, and the average ratio of the experimental and NLFEA ultimate capacity was 1.02. Finally, experimental results were used to evaluate nominal flexural strength. The comparison showed that nominal flexural strength predicts flexural stress. The average experimental-nominal flexural strength ratio was 1.14.

Simulation and analysis of rust expansion cracking of reinforced concrete

Reinforced concrete is used in complex environment, and the damage of concrete protective layer caused by steel corrosion will seriously reduce the durability of the structure. In order to deal with the different corrosion morphology of steel bars in engineering, three different function expressions are proposed to describe the uniform and non-uniform corrosion of steel bars. Based on PF_CZM phase field model and adaptive refinement mesh technology, the cracking of concrete protective layer caused by different corrosion types of steel bars is simulated. The simulation results are close to the experimental or actual observed crack propagation. The research shows that the non-uniform corrosion coefficient (α) of steel bars affects the crack propagation form of protective layer. When α=1,2, the thinnest part of the protective layer will be penetrated by the main crack, and two secondary cracks will be produced on both sides. The characteristic displacement in the process of crack propagation is similar, and the maximum expansion displacement of steel bar is less than 125 μm when there is obvious crack in the protective layer. When α=4,8, the protective layer will produce two main cracks. The corrosion characteristic displacement is also similar, and the maximum expansion displacement of steel bars exceeds 180 μm when there are obvious cracks in the protective layer. However, with the increase of non-uniform corrosion coefficient, the amount of steel corrosion required for obvious damage and cracks gradually decreases, and the structure is more likely to be damaged. When non-uniform corrosion occurs in both longitudinal and transverse directions of steel bars, cracks will originate from the most serious corrosion of steel bars and spread to both sides. Compared with the two-dimensional simulation results, the simulated crack propagation morphology and the predicted structural durability results are more accurate. The coarse mesh is used to verify the adaptability of the method to the project, which provides reference for the engineering design and durability research of concrete structures.

Quantitative Expression of the Modified Bragg's Law for Bragg resonances of water waves excited by five types of artificial bars

For Class I Bragg resonance excited by five types of finite periodic array of widely spaced bars (rectangular, parabolic, rectified cosinoidal, trapezoidal, and triangular bars), the average phase velocity between any two adjacent bars in each type of bar field has been specifically calculated by employing a mathematical transformation, and therefore, the excitation condition of Class I Bragg resonance excited by each bar field is clarified and the modified Bragg's law established by Xie and Liu becomes a quantitative form. On one hand, if the incident surface wavelength, L, is fixed in advance, then according to the excitation condition, we can directly obtain the critical bar spacing, d, at which Class I Bragg resonance occurs. On the other hand, if the bar spacing, d, is fixed, then according to the excitation condition, we can use an iteration scheme to find out the critical surface wavelength, L, at which Class I Bragg resonance will be excited. In comparison with existing experimental, numerical, and analytical results of Bragg resonance excited by the five types of bar fields, it is shown that the modified Bragg's law is much more accurate than the Bragg's law, and the phenomenon of phase downshift can be well explained. In the linear long-wave limit, owing to the simple dispersion relation, the modified Bragg's law becomes an explicit expression and coincides with Liu's approximate law very well, although the former is a straight line segment while the latter is a curved line segment. Finally, it is shown that the phase downshift of Bragg resonance becomes more significant as the cross-sectional area of bars increases.

Experimental and finite element study of bond behavior between seawater sea-sand alkali activated concrete and FRP bars

The bond performance of fiber reinforced plastic (FRP) bars in seawater sea sand alkali activated concrete (SSASC) was investigated using pull-out test specimens. The effect of different concrete strengths, anchorage lengths, FRP bar types, and diameters on the bond performance were investiaged. Special emphasis was given to the applicability of the existing bond-slip constitutive models to FRP reinforced SSASC, which was investigated by calibrating well-known models to the experimental results. The correlation between the experimental curve and different bond-slip constitutive models is analyzed by calculating the R2 value. To verify the applicability of finite element analysis to SSASC and FRP bars system, numerical simulation was performed in ABAQUS finite element simulation software by setting the same conditions as the experimental variables. The results indicate that the Fan Xiaochun’s model, which is the modifications of the MBPE model, has a high degree of correlation and is more suitable for SSASC and FRP bars system. The simulation results using ABAQUS finite element software are in good agreement with the experimental results.

Flexural stiffness of RC beams with high‐strength steel bars after exposure to elevated temperatures

AbstractIn this paper, the flexural stiffness of the reinforced concrete (RC) beams reinforced with high‐strength steel bars after exposure to different elevated temperatures was investigated experimentally and theoretically. The effects of the elevated temperature (room temperature, 200°C, 400°C, 600°C, 800°C, and 1000°C), high‐temperature duration time (0 h, 1 h, and 2 h), and steel bar types (HRB600 and HRB500) on the load–deflection response, load–stiffness response, and crack distribution of tested beams were investigated. The results showed that when the temperature is below 600°C, the effect of high temperature on the stiffness reduction of high‐strength RC beams is not significant, while the beams reduced the stiffness when the exposure temperature reached 800°C and 1000°C, regardless of the type of the steel bars. The elevated temperature accelerated the development of the deflection of RC beams, and the bending stiffness of the RC beams decreased more severely as the increase of duration time. By using appropriate degradation factors, the residual stiffness of the beams was predicted well by the analysis calculation method and the effective inertia moment calculation method, for example, the prediction accuracy is over 91% and 85.8% for the cases under and over 800°C, respectively. However, for the beams at 1000°C, a correction coefficient (0.652) was applied to improve the accuracy of the calculative stiffness of the HRB600 RC beams at the service load stage.

Biomechanical Effectivity Evaluation of Single- and Double-Metal-Bar Methods with Rotation and Equilibrium Displacements in Nuss Procedure Simulations.

Surgical treatment of the pectus excavatum has led to the introduction of the Nuss procedure, a minimally invasive surgical procedure that involves inserting a metal bar under the sternum through a small lateral thoracic incision. An additional metal bar was inserted in patients with pectus excavatum to improve the retention of the restored chest wall after the Nuss procedure. However, a need still exists to analyze the mechanistic advantages and disadvantages of the double-bar method owing to the increased surgical time and proficiency. The purpose of this study is to compare and evaluate the efficiency of single- and double-bar methods using rotational and equilibrium displacement simulations of the Nuss procedure. A finite-element model was constructed for two types of metal bars inserted into the chest wall. Boundary conditions for the rotation and equilibrium displacements were set for the metal bar. The anterior sternal translation, Haller index and maximum equivalent stress and strain owing to the behavior of the metal bar were estimated and compared with the single-bar method and postoperatively acquired patient data. The simulation results showed that the influences of the intercostal muscle and equilibrium after rotation displacement were significant. The stresses and strains were distributed across the two metal bars, and the upper-metal bar was heavily loaded. The double-bar method was advantageous regarding the load distribution effects of the two metal bars on the chest wall. However, mechanical assessments are also important because an excessive load is typically applied to the upper-metal bar.

Near-surface mounted-FRP flexural retrofitting of concrete members using nanomaterial-modified epoxy adhesives

This study, serving as the first of its kind in this scope, investigates the effectiveness of nanomaterial-modified epoxy adhesives (NMEAs) for Near-Surface Mounted (NSM)-FRP flexural retrofitting of concrete. A total of 48 concrete prisms were retrofitted using three different types of FRP reinforcement bars (CFRP, GFRP and BFRP) inserted in grooves sized 8 × 8, 10 × 10 or 12 × 12 mm and bonded to the concrete substrate using either neat epoxy (NE) or NMEAs. NMEAs were developed by incorporating either carbon-based (i.e. CNF, cellulose and graphite) or silicon-based (i.e. silica and MMT clay) nanoparticles into epoxy at 0.1 wt. %, whereas the graphite NMEAs were prepared with more wt.% (i.e. 0.2 and 0.3). SEM and XRD techniques were used to assess the dispersion quality of nanoparticles within the matrix along with the porosity and crystallinity percentages of the NMEAs. Results showed that using silica, clay and graphite NMEAs rather than NE enhanced the retrofitted concrete capacities, whereas a decrease in strength was observed when using CNF- and cellulose-modified epoxies. Moreover, it was found that the specimens bonded with silicon-based NMEAs had, on average, higher capacities than those bonded with carbon-based NMEAs, which, on the other hand, showed more ductile behaviour. Results also suggested that the specimens’ capacities decreased as the wt. % concentration of the nanoparticles (i.e. graphite) increased. Increasing the groove size from 8 × 8 mm to 10 × 10 mm decreased the capacities but enhanced the ductility, whereas increases in both the capacities and ductility were achieved when moving from 8 × 8 mm to 12 × 12 mm.

Pull-Out Tests for GFRP/BFRP/Steel Bars Used as Nailing for Coal-Bearing Soil Slopes in Humid Regions

Abstract Coal-bearing soil slopes are associated with a high risk of landslides when subjected to high soil water content. Steel bars have been used as soil nailing for slope stabilization; however, corrosion may occur in an aggressive environment. Glass fiber reinforced polymer (GFRP) and basalt fiber reinforced polymer (BFRP) bars have higher resistance to corrosion and could be alternatives to steel bars, but their elastic modulus and bonding strength with cement concrete are inferior to steel bars, which may result in lower reinforcement effects against landslides and hence require further investigation. In this study, the mechanical properties of different types of bars were investigated using tensile tests. The mineral composition of the soil samples was analyzed. Subsequently, pull-out tests were conducted on three types of bars (steel, GFRP, and BFRP) embedded in grouts in the soil. Up to 38 test scenarios were investigated, and the results were statistically analyzed using an analysis of variance test. The effects of several factors were studied, including the bar type, water content, soil compaction degree, and soil surcharge. The results showed that the bar type had an insignificant effect on the maximum pull-out loads, indicating the feasibility of using GFRP and BFRP bars as alternatives to steel bars for soil nailing in coal-bearing soil slopes. The reinforcement effect can be weakened by rainfall or drought events and enhanced by higher compaction energy and surcharge loads.