Bond-slip Behavior Research Articles

The bond-slip behavior of H-shaped steel embedded in UHPC under reversed cyclic loading

To investigate the bond-slip behavior of the interface between H-shaped steel and ultra-high performance concrete (UHPC) under reversed cyclic loading, 18 steel-UHPC and 6 steel-NC composite specimens were fabricated and subjected to both reversed cyclic and monotonic loading tests. Key parameters including concrete strength, steel fiber volume fraction, embedded length of the steel section, and loading scheme were examined. The results indicate that, under reversed cyclic loading, the bond strength of the steel-UHPC composites decreased by 7 %–15 %, while the residual bond strength decreased by 16 %–57 % compared to monotonic loading. For both loading schemes, bond strength slightly decreases with an increase in embedded length but can be significantly enhanced by increasing the steel fiber volume fraction, which also improves residual bond strength and energy dissipation under reversed cyclic loading. Additionally, bond strength increases with higher concrete strength. Finally, a damage index D derived from the bond stress-slip hysteresis curves was used to represent bond degradation under reversed cyclic loads, and a constitutive model to predict the bond-slip behavior of the steel-UHPC interface under reversed cyclic load was presented.

Numerical Investigation of the Bond-Slip Behavior between Double-Helix BFRP Macrofibers and Concrete

Numerical Investigation of the Bond-Slip Behavior between Double-Helix BFRP Macrofibers and Concrete

Bond-Slip Behavior Between C-Shaped Steel and Foamed Concrete in CTS Composite Structural Members

The bond-slip behavior between cold-formed thin-walled steel (CTS) and foamed concrete (FC) is a critical issue in the mechanical performance of FC-filled CTS composite wall structures. Thus, this study provides experimental and theoretical research on the bond-slip behavior between CTS and FC. A total of eleven specimens were tested using push-out configurations, considering the number of web holes, foamed concrete (FC) strength, anchorage length, and CTS section splice form. A constitutive model for bond-slip was proposed, and the regression formulas for accurately predicting the characteristic bond strength between CTS and foamed concrete were established. A finite element model was developed to investigate the bond-slip mechanism at the interface between CTS and FC. The bond-slip constitutive model accurately fits the experimental and finite element results. The results indicate that the ultimate bond strength of the specimens increases with the number of web holes; when the number of web holes reaches two, the ultimate bond strength is 155.4% of that of the non-perforated specimens. As the concrete strength increases from 3.43 MPa to 11.26 MPa, the ultimate bond strength of specimens with two web holes improves by 23.1%, while non-perforated specimens have a 54.7% enhancement. When the anchorage length is extended from 200 mm to 400 mm, the ultimate bond strength decreases by 29.3%. Additionally, when steel sections are joined in a double-span I form, the bond strength increases by 91.6% and 95.8% compared to the single-span form and the double-span box form, respectively.

Bond–Slip Behavior of High-Strength Stainless Steel Wire Mesh in Engineered Cementitious Composites: Numerical and Theoretical Analysis

Bond–Slip Behavior of High-Strength Stainless Steel Wire Mesh in Engineered Cementitious Composites: Numerical and Theoretical Analysis

Experimental and numerical investigations on the bond-slip behavior of the interface between geopolymer concrete and steel tube

This study conducts push-out tests on eight geopolymer concrete filled steel tube column specimens with varying design parameters to evaluate the effects of steel tube wall thickness, concrete strength, and the presence of welded longitudinal ribs on the bond-slip performance at the interface between geopolymer concrete and steel tube. The study analyzes the influence mechanism of chemical bonding force, mechanical bite force, and friction resistance on bond strength and a three-stage bond-slip constitutive relationship is established. The results indicate that steel tube strain increases with height, with significant strain observed at the welding structure and the fixed end of the steel tube. The length-to-diameter ratio, diameter-to-thickness ratio, concrete strength, and construction measures of the steel tube are identified as key factors in enhancing interfacial bonding performance. The presence of welded longitudinal ribs on the inner wall of the steel tube significantly improves the interface bonding. The calculated bond strength ratios, compared with the test results, fall within an 11% margin, demonstrating good agreement.

Influence of Specimen Width on Crack Propagation Process in Lightly Reinforced Concrete Beams.

Models used to study the fracture process of concrete are often considered 2D, ignoring the influence of specimen width. However, during the fracture process in pre-cracked concrete beams, the crack length varies along the thickness direction, especially in reinforced concrete. To study the influence of specimen width on reinforced concrete fracture behavior, a 3D numerical method was used to simulate the crack propagation processes of lightly reinforced concrete beams based on Fracture Mechanics. Nonlinear spring elements with different stress-displacement constitutive laws were employed to characterize the softening behavior of concrete and the bond-slip behavior between the steel bars and concrete, respectively. It is assumed that the crack begins to propagate when the maximum stress intensity factor at the crack tip along the beam width reaches the initial fracture toughness of concrete. To verify the validity of the proposed method, the completed crack propagation processes of lightly reinforced concrete three-point bending notched beams were simulated, and the calculated load-crack mouth opening displacement curves showed a reasonable agreement with the experimental data. Moreover, the impact of the 2D reinforced concrete beam model on the crack propagation process was analyzed. The results indicate that at the initial loading stage, the external load P obtained from the 2D model is significantly larger than the result from the presented 3D model.

Early age bond-slip behavior of reinforcing steel bars in concrete subjected to uniaxial lateral pressure: An experimental study

The bond between reinforcing bars and concrete is a crucial factor concerning the serviceability of reinforced concrete structures, particularly for those during construction in some developing areas where plain bars were still used as reinforcements. Despite numerous studies on early age bond behavior between steel bars and concrete, little research has been conducted to quantify the effect of uniaxial lateral pressures on this bond. This study involved testing a total of 378 pullout specimens to evaluate the early age bond-slip behavior of plain bars in concrete under uniaxial lateral pressure. The main test parameters included the concrete ages (1, 3, 7, 14 and 28 days), lateral pressures (0, 0.1, 0.2, 0.4 and 0.6 times the compressive strengths of concrete), concrete strength grades (C20, C35 and C45), and bar diameters (12, 16 and 20 mm). Based on the experimental results, a series of analytical expressions were developed for bond strength, maximum bond slip and residual bond stress predictions considering the effects of early age and lateral pressure. The results demonstrate that degradation of bond strength at early ages can be effectively mitigated by uniaxial lateral pressures. As the age decreases from 28 to 1 days, the bond strength exhibits a significant decrease of up to 51.59 %, while this adverse effect can be reduced by around 10 % in the presence of lateral pressures. Increasing the pressure level from 0 to 0.4 results in a significant increased early age bond strength by 112.6 % to 199.0 % for different bar diameters. However, the residual-to-maximum bond stress ratio remains nearly constant at 0.49 regardless of age and lateral pressure, as the pressure primarily contributes to frictional forces at the bar-concrete interface. An age-dependent bond-slip constitutive model considering the effect of uniaxial lateral pressures was finally proposed and verified with the test results. The paper concludes that given the concrete compressive strength at 28 days, the proposed bond strength and bond stress-slip models can predict the early age bond responses of plain bars in concrete under uniaxial lateral pressures with reasonable accuracy.

Study on the deformation of hybrid BFRP-steel reinforced concrete beams considering crack development

Hybrid fiber-reinforced polymer (FRP)-steel reinforced concrete (RC) beams exhibit various flexural failure modes depending on different equal-stiffness reinforcement ratios, the post-yield stiffness ratio, and the bond-slip behavior. This study first develops a model for the tensile behavior of hybrid Basalt FRP (BFRP) -steel reinforced concrete chords, considering the modified Bertero-Popov-Eligehausen (mBPE) bond-slip model. The rationality of the tensile stiffening model was validated through comparisons with existing experimental tests on the axial tension of chords. Subsequently, a beam deformation correction calculation method considering ‘rigid-rotation’ was proposed. The corrected theoretical calculation of the beam’s peak load shows an error of 5.0% compared to the experimental value, while modified ultimate deformation exhibits an error of 4.7%. As the bond weakens, the theory proposed in this paper is more suitable for predicting the deformation capacity of hybrid reinforced beams. ACI 440.1R-15 underestimate deformations by approximately 77.8%, limiting the normative evaluation of deformation calculations for hybrid reinforced concrete beams considering bond slip. Finally, the influence of bond-slip parameters ( τm, sm and [Formula: see text]) and reinforcement configurations (equal stiffness reinforcement ratio, steel/BFRP reinforcement ratio, and post-yield stiffness ratio) on beam deformation and crack width was investigated. The results indicate that the peak bond strength is a key parameter affecting crack width and deformation of the beam. The exponential rise segment parameter α and the slip sm corresponding to peak bond strength mainly influence the load level corresponding to cracking.

Effect of elevated temperature on the bond behaviour of adhesive shear joints between glass substrate and iron-based shape memory alloy strip

Glass has been increasingly used as structural elements, such as glass beams or fins. Previous feasibility studies have shown increased initial and post-fracture load-bearing capacity of laminated glass beams post-tensioned with adhesively bonded iron-based shape memory alloy (Fe-SMA) strips. However, the potential elevated service temperatures were not considered, which significantly degraded the material properties of the adhesive. This study experimentally investigated the mechanical behaviour of Fe-SMA-to-glass lap-shear joints with an epoxy adhesive at different temperatures of 23 °C, 50 °C, and 80 °C, representing room temperature and typical elevated service temperatures. The results showed that, compared with the one at room temperature, the load-carrying capacity remained nearly unchanged at 50 °C and decreased by approximately 20 % at 80 °C. On the contrary, the effective bond length increased from approximately 116 mm to 250–300 mm. The failure modes, the tensile strain of the iron-based shape memory alloy, the bond-slip behaviour, and the fracture energy of the joints were also evaluated. The current study fills a significant research gap in the engineering application of strengthening glass structures by bonded pre-stressed Fe-SMA strips. Moreover, the results may also significantly contribute to the future application of the selected adhesive at elevated temperatures.

Modeling the bond–slip behavior of the interface between a stiffened core and cemented soil based on machine learning approaches

The bond–slip behavior of stiffened deep cement mixing (SDCM) piles—which is crucial for their bearing capacity—evolves continuously with curing age. In the study reported here, 20 element tests were conducted on the interface between cemented soil and a stiffened core, analyzing the bond–slip behavior affected by curing temperature and age, and then ensemble learning methods (XGBoost, random forest) were used to establish models for the evolution of the bond–slip behavior considering thermal effects. The constructed models can predict the peak shear strength (τmax), the residual shear strength (τres), and the interfacial shear modulus (G). The test results show that the shear strength of the stiffened-core–cemented-soil interface grows with the increasing curing temperature and age, with faster growth at 0–14 days compared to 60–90 days. To lessen the reliance on ineffective brute-force searching, Bayesian optimization with a tree-structured Parzen estimator is used to select the hyperparameters of the established models. The results demonstrate the superior performance of the chosen approach, with R2 > 0.93 for the training set and R2 > 0.81 for the test set. The results of the XGBoost model are best for τmax, with a mean absolute percentage error of less than 5 %, thereby enabling accurate predictions of the mechanical parameters of the stiffened-core–cemented-soil. This research enhances the understanding of the mechanical properties of SDCM piles and provides valuable guidance for projects involving such piles.

Bond between single and bundled high-modulus ribbed GFRP bars with short embedment lengths and concrete

The bond between glass fiber-reinforced polymer (GFRP) rebar and concrete is one of the most important parameters in the design of GFRP-reinforced structures. This study investigates the bond behavior of single and bundled high-modulus ribbed GFRP rebars with short embedment lengths in concrete. To achieve this, a total of 48 pullout specimens were constructed and tested. The effect of various parameters, including GFRP rebar embedded length, the concrete block dimensions, GFRP surface characteristics, presence of transverse reinforcement, and bundling of rebars on the bond behavior of high-modulus ribbed GFRP rebar was studied. The experimental results indicated that the failure mode changed from pullout to splitting failure as the embedment length increased. The presence of transverse reinforcement, in many cases, changed brittle splitting failure to partial splitting failure followed by pullout failure. The variation in rebar surface characteristics resulted in differences in the bond-slip behavior of GFRP rebar in concrete. The experimental findings illustrated that rebar stress at failure for specimens with bundled GFRP was generally higher than that of corresponding individual bar with approximately same cross-sectional area. This observation suggests that the equivalent area method may serve as a conservative approach for evaluating the embedment length of bundled ribbed GFRP rebars. Furthermore, the adhesion between ribbed GFRP rebars and concrete was quantified for various bar sizes. Finally, the experimental results were employed to refine and calibrate existing bond-slip models of ribbed GFRP rebar to concrete.

Experimental and analytical investigations on bond–slip behavior of steel reinforcement inUHPFRCconsidering yielding

AbstractThe bond behavior between ultra‐high‐performance fibre‐reinforced concrete (UHPFRC) and steel rebars plays an important role in the load‐bearing capacity and serviceability of structural members. A suitable bond–slip model is essential for predicting the load resistance and deformation capacity of members, after cracking of the UHPFRC. This paper studies the bond strength between ribbed steel bars and the surrounding UHPFRC before and after yielding of the steel reinforcement. To determine the corresponding bond–slip relationship, pull‐out tests, with varying embedment lengths of the reinforcement, namely 2 times and 10 times the rebar diameter, and diameter of reinforcing bars ranging from 10 mm to 16 mm were conducted. The bond stress, strain and slip along the embedment length of the steel rebars were measured by strain gauges and displacement transducers. Based on the test data, a bond stress–slip model was derived before (elastic stage) and after (inelastic stage) yielding of the reinforcement. The slip at the yield point is suggested through theoretical equations. The post‐yield bond–slip model is based on yield bond stress and frictional bond stress. The two‐part model was validated through iterative procedures and is able to predict the applied force, bond stress and strain distribution along the reinforcing bar. A comparison between the test data and analytical results demonstrates a good predictive capacity on the bond behavior of reinforcement in UHPFRC both before and after yielding of the reinforcement.

Corrosion failure analysis of interfacial bond performance in circular seawater sea-sand concrete encased weathering steel structures

This paper investigated the bond-slip behavior of circular seawater sea-sand concrete encased weathering steel (CSSCEWS) structures after chloride-induced corrosion. Electrochemical corrosion tests and push-out tests were conducted on fifteen designed CSSCEWS specimens. The results revealed that the corrosion ratio and steel section type distinctly influenced the interfacial bond performance. Both the ultimate and residual bond strengths decreased with the increase of the corrosion ratio, and the decline rate slowed down gradually. Compared to the uncorroded specimens, the average damage ratio of the ultimate strength of the specimens with a corrosion ratio of 8% is 25.9%, while the average damage ratio of the residual strength is 49.1%. The bond toughness continuously decreased with prolonged corrosion, while the bond stiffness and energy dissipation index first increased and then decreased. Additionally, formulas for calculating the corroded bond strengths of CSSCEWS specimens were proposed. Considering the strength damage due to corrosion and the stiffness damage due to slip, a three-stage bond-slip constitutive model was proposed. Finally, this model was applied to the nonlinear spring elements in finite element modeling to effectively simulate the interfacial bond behavior during the loading of corroded CSSCEWS specimens.

Out-of-plane performance of BFRP reinforced UHPC thin panel: experiment and numerical analysis

In this study, the out-of-plane performance of ultra-high performance concrete (UHPC) thin panels reinforced with basalt fiber reinforced polymer (BFRP) bars was investigated. Eight panels were tested under four-point load, with the investigating parameters including panel thickness, reinforcement ratio, and the presence of steel fibers. The failure mode, crack pattern, load vs. mid-span displacement, and reinforcement strain relationships were studied. Test results revealed that panels with a higher thickness (70 mm) exhibited 178.6% higher initial stiffness, 34.5% higher cracking loads, and 88.7% higher peak loads compared to those with a lower thickness (50 mm). The effects of a larger reinforcement ratio and the presence of steel fibers became more pronounced after concrete cracking, leading to 21.2% and 22.1% higher post-cracking stiffness, respectively. Adding steel fibers helped control the development of diagonal cracks and shifted the panel failure mode from shear to flexural failure. Based on the comparison of test results with design codes, the expressions in CAN/CSA-S806-12 were recommended for predicting the load-carrying capacity of the specimens. Furthermore, a two-dimensional finite element (FE) model was developed to reproduce the test results, which validates the adopted CDP model for UHPC and the bond-slip behaviors between UHPC and BFRP bars.

Effect of coarse aggregate concentration on the bond properties between steel rebar and concrete within low and medium strength range

Most of the current rules and practices employ medium and high-strength concrete with ribbed rebar. However, there are still many structures that are of low concrete class with non-standard aggregate gradation and also contain plain rebar. In this study, to better understand the behavior of such structures, concrete mixtures with 3 different water-to-cement (W/C) ratios (0.6–0.9–1.2) and 4 different coarse aggregate concentrations (CAC) (0 %-20 %-40 %-60 %) were produced. Compressive strength (CS), elasticity modulus (MOE), and splitting tensile strength (STS) tests were performed on the concrete samples, and the stress-strain relationship was determined. Bond-slip behavior was examined on samples containing both plain and ribbed rebars. The results showed that 40 % CAC mixtures had the highest CS and 60 % CAC mixtures had the highest MOE. Adding coarse aggregate increased STS, bond strength (τu), and residual bond stress (τr). The results obtained from this study were also combined with a similar study conducted on medium and high-strength concrete, and models were proposed for CS, MOE, and τu, τr. It was determined that similar to compressive strength, the MOE was also effective on bond strength significantly. A machine learning method (random forest regression) and feature importance analysis were performed to support the results. The results revealed that CS has the most significant effect on τu and τr, but the effect of MOE and STS was also very significant. Additionally, τr/τu and the s1 (slip value at τu), which is proposed as a constant value in existing studies, increased with increasing CS.

Bond-slip behavior of Aluminum Alloy (AA) bars for near-surface mounted (NSM) technique

An experimental study consisting of 22 pull-out tests was carried out to investigate the bond-slip performance and load transfer mechanism between near-surface mounted (NSM) Aluminum Alloy (AA) bars and concrete when the AA bars are inserted into pre-cut grooves on the surface of the host structure and bonded with an appropriate bonding agent. The effects of several design parameters were evaluated including bond length, diameter of AA bars, bar surface treatment, and adhesive type. A digital image correlation (DIC) system was used to measure the slips and surface strain and four failure modes were observed in the tests, being concrete splitting failure, epoxy splitting, debonding at the bar-epoxy interface, and AA bar rupture. Results showed that an increase in bond length could make the failure mode more ductile, while AA bars with rough surfaces exhibited a relatively satisfactory bond-slip behavior when a suitable epoxy was used. Finally, the test data from this study were used to examine three bond-slip models based on fiber reinforced polymers (FRP) for the NSM technique. A new bond-slip model considering the influence of the bar external surface was proposed and validated by the test results from both this study and literature.

Bond–Slip Behavior of Concrete Pile–Cemented Soil Interface Considering Thermal–Temporal Effect: Experimental Study and Constitutive Modeling Based on Disturbed State Concept

Bond–Slip Behavior of Concrete Pile–Cemented Soil Interface Considering Thermal–Temporal Effect: Experimental Study and Constitutive Modeling Based on Disturbed State Concept

Influence of mechanical anchors on bond performance of fiber fabric-steel joints

This study proposes an experimental model for anchor reinforcement and conducts uniaxial static tensile tests. The influence of anchor reinforcement on the failure mode of specimens is revealed. This includes the effects of bond length, number of layers, and types of fiber fabric under anchor reinforcement on the ultimate bearing capacity and bond-slip curve. The results demonstrate that anchors can effectively increase the ultimate bearing capacity of the test specimens. There are differences in bond-slip behavior between the anchors near the free end and the joint end. Higher stresses are experienced near the joint end. The use of anchor reinforcement can significantly enhance the load-bearing capacity of multi-layer carbon fiber specimens. Increasing the number of anchors and reducing the distance between the anchor and the joint end can further improve the stiffness of the specimens. A finite element model is established using ANSYS, which agrees well with the experimental results and parameterized analysis results reveal a linear increase in load-bearing capacity and stiffness with higher anchor bolt preload, achieving an 84.42 % increase at 11kN. Increased preload enhances friction at the carbon fiber-steel interface, reducing deformation. Similarly, expanding anchor width from 9 mm to 39 mm improves load-bearing capacity by 54.28 %, with larger anchors significantly boosting stiffness and bonding performance, which can be used to predict the mechanical properties of fiber fabric-steel reinforced by anchors.

Experimental analysis of the bond-slip characteristics between CFRP and natural stone masonry units

Purpose Although the reinforcement of concrete and brick masonry with fiber-reinforced polymer (FRP) has been extensively researched, its application and impact on natural stone, especially in historic preservation, have received less attention. This study aims to examine the bond-slip characteristics of carbon fiber-reinforced polymer (CFRP) with two types of natural stone masonry, aiming to enhance their effectiveness in reinforcing historic structures. The stones studied include one from the Chouf-Lekdad region (A) and another from a historic structure in Sétif City (B). Both stones were strengthened using CFRP and carbon fiber fabric (CFF) through near-surface mount (NSM) and external bonding (EBR) techniques. Design/methodology/approach The interaction was assessed during the pull-out test by analyzing the stress transfer mechanisms, adhesion and deformation. This study also examines the effects of the following parameters on the bond between CFRP and stone: type of stone (A and B), type of reinforcement (plat CFRP and CFF), various notch shapes and sizes (bp, tp and Lb), and reinforcement techniques (NSM and EBR). Findings This study demonstrated the practicality and effectiveness of enhancing natural stone masonry of old buildings by integrating NSM and EBR techniques with CFRP. With a bond length of 30 mm, the pull-out force correlates with the strength of the stone. This indicates the importance of stone strength in obtaining better adhesion. The CFF–resin interface is more cohesive than the CFRP plate–resin interface because the resin penetrates the flexible CFF strip, ensuring better adhesion. In contrast, the CFRP plate interface is rigid and smooth. The results suggest that natural stone–CFRP adhesion is more effective than CFRP bonded to concrete and brick masonry due to the stone's strong resistance. Originality/value This experimental investigation provides new study into the bond-slip behavior of CFRP-reinforced natural stone masonry, filling the gap in existing research. The findings offer useful direction for creating FRP strengthening solutions that are specifically adapted to the properties of natural stone used in historic constructions. This study helps to improve preservation procedures by guiding the selection of reinforcing techniques, such as NSM versus EBR, and finding ideal bond lengths. This work's novelty stems from its ability to improve the structural integrity of culturally significant buildings while preserving their historical authenticity.

Study on bonding properties and constitutive model of steel bar and nano-SiO2 reinforced recycled aggregate concrete

Optimizing design and ensuring the structural safety of recycled aggregate concrete (RAC) structures requires a thorough understanding of the bond-slip mechanism between steel bars and RAC. Previous studies have demonstrated the significant enhancement of the microscopic properties of RAC and its bond with steel bars due to nano-SiO2. However, the structural bonding mechanism between the steel bar and nano-SiO2-enhanced RAC remains unclear. Therefore, this study investigates the influence of nano-SiO2 on the bond performance between RAC and steel bars, elucidating the enhancement mechanism through microscopic techniques. Additionally, various factors affecting the bond-slip performance of RAC specimens are analyzed, leading to establishing a multifactorial coupling formula considering thickness-to-diameter ratio, concrete strength, and relative anchorage length. Furthermore, slip index correction formulas and a constitutive model are developed, considering these factors. Acoustic emission (AE) technology monitors the bonding process, clarifying the evolution of AE digital signals and bond damage history. Employing the finite element method, a numerical model of bond-slip behavior is established, revealing specimens' changing bond strength and failure modes. Experimental results indicate that increasing nano-SiO2 content reduces structural porosity, leading to denser and more homogeneous microstructures, thereby enhancing RAC's mechanical properties and bonding performance. Moreover, AE techniques effectively monitor bond damage at different stages. Finally, a bond-slip constitutive model is proposed for steel bar and nano-SiO2 reinforced RAC, offering insights for numerical calculations and engineering designs.