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To prevent the early breakage of anchor cables under shear loads in support engineering, a combined structure of Anchor Cable with C-shaped Tube (ACC) has been proposed. The shear resistance enhancement mechanism of this structure and the mechanisms of various influencing factors have yet to be fully revealed. A refined nonlinear finite element model of ACC was original established using ABAQUS software, taking into account the actual structure of the steel strands and the interactions, such as contact and failure between the various components. Various anchor cable pretension forces and block strengths were set to investigate their effects on the shear mechanical response of ACC. The results successfully demonstrated a high correlation between peak shear load and pretension force. The results demonstrate that an increase in pretension force reduces the ACC's peak shear load and break displacement. Additionally, the structure exhibited higher flexural stiffness, the block strength was mobilized earlier, and the block failed locally more quickly. Under high pretension forces, the system exhibited higher shear stiffness in the early stages of shearing due to the influence of the axial force component. With low pretension forces, the ACC exhibited a larger break displacement due to the minor tensile deformation at the shear plane position for the same shear displacement. At low pretension forces, the structure's bending angle increased more rapidly during the middle and later stages of shearing, accompanied by a larger break displacement. Both of these factors led to a greater bending angle at the shear plane position at the point of failure. The results reveal the characteristic of the peak shear load initially increasing and then decreasing with the increase in test block strength, along with its underlying mechanism. As the block strength increased, the bending angle of the structure at the shear plane position increased more rapidly, resulting in higher shear stiffness. With high block strength, the combination of smaller break displacement and greater shear stiffness led to an initial increase followed by a decrease in peak shear load. A comprehensive RSSB (Relative Stiffness between Structure and Test Block) that considers both structural and test block stiffness was proposed. The deformation pattern of the structure was controlled by the RSSB. The higher the RSSB, the wider the plastic hinge extension range for the same shear displacement, the smaller the bending angle at the shear plane position, and the smaller the maximum curvature of the structure. The contact force of the C-shaped tube generally exhibited a "single peak" distribution. As the shear displacement increased, the peak position of the contact force moved away from the shear plane, and the maximum contact force increased rapidly and remained relatively stable. At the end of the shearing process, the contact force of the C-shaped tube exhibited a "double peak" distribution. [ABSTRACT FROM AUTHOR]

Abstract To prevent the early breakage of anchor cables under shear loads in support engineering, a combined structure of Anchor Cable with C-shaped Tube (ACC) has been proposed. The shear resistance enhancement mechanism of this structure and the mechanisms of various influencing factors have yet to be fully revealed. A refined nonlinear finite element model of ACC was original established using ABAQUS software, taking into account the actual structure of the steel strands and the interactions, such as contact and failure between the various components. Various anchor cable pretension forces and block strengths were set to investigate their effects on the shear mechanical response of ACC. The results successfully demonstrated a high correlation between peak shear load and pretension force. The results demonstrate that an increase in pretension force reduces the ACC’s peak shear load and break displacement. Additionally, the structure exhibited higher flexural stiffness, the block strength was mobilized earlier, and the block failed locally more quickly. Under high pretension forces, the system exhibited higher shear stiffness in the early stages of shearing due to the influence of the axial force component. With low pretension forces, the ACC exhibited a larger break displacement due to the minor tensile deformation at the shear plane position for the same shear displacement. At low pretension forces, the structure’s bending angle increased more rapidly during the middle and later stages of shearing, accompanied by a larger break displacement. Both of these factors led to a greater bending angle at the shear plane position at the point of failure. The results reveal the characteristic of the peak shear load initially increasing and then decreasing with the increase in test block strength, along with its underlying mechanism. As the block strength increased, the bending angle of the structure at the shear plane position increased more rapidly, resulting in higher shear stiffness. With high block strength, the combination of smaller break displacement and greater shear stiffness led to an initial increase followed by a decrease in peak shear load. A comprehensive RSSB (Relative Stiffness between Structure and Test Block) that considers both structural and test block stiffness was proposed. The deformation pattern of the structure was controlled by the RSSB. The higher the RSSB, the wider the plastic hinge extension range for the same shear displacement, the smaller the bending angle at the shear plane position, and the smaller the maximum curvature of the structure. The contact force of the C-shaped tube generally exhibited a “single peak” distribution. As the shear displacement increased, the peak position of the contact force moved away from the shear plane, and the maximum contact force increased rapidly and remained relatively stable. At the end of the shearing process, the contact force of the C-shaped tube exhibited a “double peak” distribution.

This paper investigates the interfacial bonding behavior between high toughness resin concrete with steel wire mesh (HTRCS) and concrete. A total of five sets of fifteen double shear specimens were tested for parameters including concrete strength and material properties of HTRCS composites. The test results showed that the failure mode of DS1 specimens was partial debonding and fracture, and the rest of the specimens were the fracture of HTRCS. The concrete strength and reinforcement ratios of HTRCS composites were positively correlated with interfacial adhesion properties. When the concrete strength was increased from C30 to C40 and C50, the ultimate load increased by 43.4% and 43.2%, respectively. The ultimate load capacity increased by 32.1%, with the reinforcement ratio of HTRCS composites increasing from 1.05% to 1.83%. Moreover, the bonding slip model and the bearing capacity formula for the interface between HTRCS composites and concrete were proposed, and the calculation values were in good agreement with the test values, with an average value of 0.978. [ABSTRACT FROM AUTHOR]

In this paper, eight shear tests were carried out utilising a double shear with infilled shear interfaces after determining an appropriate experimental design and modified testing scheme. For this, two rock bolts, 20 and 30 tonnes, were tested with modified double shear testing apparatus at different pretension loads. The infilled test scheme was conducted with 5 mm thick sandy clay infilled shear interfaces. A 40 MPa small aggregate concrete was used for all samples to simulate the host rock. Based on the shear profiles, it was found that all samples followed a three-part failure profile consisting of elastic, strain softening, and failure regions. The results of double shear tests revealed that the 20 tonne rock bolt saw a significant overall decrease of approximately 30% in its failure displacement response as opposed to the 30 tonne samples, which saw a 6% increase. Also, it was concluded that the 30 tonne samples outperformed the 20 tonne rock bolts by up to 30%, irrespective of initial pretension settings. Comparing the physical failure characteristics of the samples found that both the 20 and 30 tonne samples exhibited the same response to increased pretension. As the pretension increased, the angle experienced at the hinge point also increased incrementally. [ABSTRACT FROM AUTHOR]

The bond between fiber-reinforced composites and concrete plays a critical role in reinforcing concrete structures and composite constructions. The study conducts a comprehensive investigation on the uniaxial tensile behavior of steel-reinforced engineered cementitious composites (ECC) and the bond behavior of reinforced ECC-concrete interface. Fifteen steel reinforced ECC specimens were tested under uniaxial load to experimentally evaluate the effect of reinforcement ratio on tensile behavior. Twenty-seven specimens were tested under double-shear conditions to experimentally evaluate the bond behavior of the reinforced ECC-concrete interface. The experimental results demonstrated that the steel reinforcement can significantly improve the ultimate tensile load of ECC and effectively inhibit the generation and propagation of cracks. Furthermore, a simplified model was proposed to predict the uniaxial tensile behavior of steel reinforced ECC. As the reinforcement ratio, width and thickness increased, the bond strength increased, in which the width and thickness serve as the main contributor to the bond strength. Based on the experimental results, a simplified bond-slip constitutive model for the reinforced ECC-concrete interface was proposed by modifying the existing bond-slip constitutive model, which is shown to be able to accurately describe the bond-slip relationship between reinforced ECC and concrete in ascending stage.

In this paper, after determining an appropriate experimental design and testing scheme to test the shear performance suitably, the impacts of pretension and shear interfaces on fibreglass rock bolts were investigated. For this purpose, at the first stage, the double shear testing apparatus was modified to address the issues and shortcomings of the established testing methodology. Then, 20-tonne and 30-tonne rock bolts were tested with pretension loads of 0 kN, 10 kN, 15 kN, and 20 kN for each test scheme. For this, a 40 MPa small aggregate concrete was used for all samples to simulate the host rock. The grout used to anchor the rock bolts was mixed to the product's recommended guidelines to ensure close resemblance to field mixtures. To maintain consistency, all samples were manufactured with the same concrete and grout recipes. The results of double shear tests revealed that increasing the pretension also increased the confining pressures at the shear interfaces for clean joints. This, in turn, reduced the damage propagating from the bolt at the shear interface and decreased the hinge point bending. The results can be applied for further analytical and numerical studies, which could utilise for a better understanding of the shear behaviour of fibreglass rock bolts. Highlights: Two types of fibreglass rock bolts, the 20-tonne and 30-tonne rock bolts, were tested utilising the modified double-shear apparatus. The double-shear testing apparatus was modified to address the issues and shortcomings of the established testing methodology. The double shear performance profiles of the bolts could be described by three regions categorised as the elastic, strain-softening, and failure regions. Increasing the pretension of each rock bolt type resulted in a reduction in the severity of the recorded shear force dip. The increased pretension yielded less physical damage to the rock bolt propagating away from the shear plane. [ABSTRACT FROM AUTHOR]

Active support using highly prestressed cable bolts and anchor cables has become a mainstream support technology for coal mine roadways. However, the ability of bolts and anchor cables to withstand transverse shear decreases with the prestress level, jeopardizing mining safety. This study proposed a technical solution to this problem featuring anchor cables enclosed in an axisymmetrical tube with a C-shaped cross-section (ACC), which are highly prestressed and can withstand high transverse shear. The ACC mechanical performance was tested in the #318 gas extraction roadway of the Shuangliu Coal Mine, China, characterized by extensive deformation under original support conditions. Theoretical analysis, laboratory tests, numerical simulation, and field tests were performed to analyze the shear mechanical properties of the ACC and anchor cables alone. The double shear test results revealed that the proposed ACC scheme increased the transverse shear resistance and stiffness by 10–25% and 20–40%, respectively. The FLAC3D numerical simulation showed that the roof-and-floor and rib-to-rib convergences decreased by 9.53 and 25.11%, respectively. The area of the stress concentration zone also decreased. Field monitoring showed that the ACC achieved good support performance. During the monitoring period, the maximum roof-and-floor and rib-to-rib displacements were 40 and 49 mm, respectively. The ACC scheme offered adequate shear resistance and effectively controlled surrounding rock deformation in the gas extraction roadway under study, making it applicable to similar engineering scenarios. [ABSTRACT FROM AUTHOR]

This paper investigates the interfacial bonding behavior between high toughness resin concrete with steel wire mesh (HTRCS) and concrete. A total of five sets of fifteen double shear specimens were tested for parameters including concrete strength and material properties of HTRCS composites. The test results showed that the failure mode of DS1 specimens was partial debonding and fracture, and the rest of the specimens were the fracture of HTRCS. The concrete strength and reinforcement ratios of HTRCS composites were positively correlated with interfacial adhesion properties. When the concrete strength was increased from C30 to C40 and C50, the ultimate load increased by 43.4% and 43.2%, respectively. The ultimate load capacity increased by 32.1%, with the reinforcement ratio of HTRCS composites increasing from 1.05% to 1.83%. Moreover, the bonding slip model and the bearing capacity formula for the interface between HTRCS composites and concrete were proposed, and the calculation values were in good agreement with the test values, with an average value of 0.978.

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the complex asymmetric deformation characteristics of inclined coal seam roadways and the tensed shear failure of anchor cable supports, the asymmetric support scheme of an anchor cable with a C-shaped tube is proposed. In order to study its supporting effect on an inclined coal seam roadway, this paper first explores the difference in shear performance between an anchor cable with a C-shaped tube and an anchor cable through double shear tests. Then, based on the asymmetric deformation characteristics of an inclined coal seam roadway in the Pangpangta Mine, a numerical simulation is used to study the asymmetric support effect of an anchor cable with a C-shaped tube in an inclined coal seam roadway. The results of the double shear test show that the anchor cable with the C-shaped tube has stronger resistance to shear load than that of the anchor cable. Through the results of the numerical simulation, the original stress field distribution on both sides of the roadway was found to be uneven due to the influence of the coal seam dip angle, and after the excavation of the inclined coal seam roadway, the displacement and plastic zone distribution on both sides showed obvious asymmetric characteristics. Compared with the symmetric support, the asymmetric support can obviously alleviate the asymmetric deformation characteristics of the two sides and effectively control the deformation and plastic failure zone of the roadway. The anchor cable with the C-shaped tube has better resistance to shear deformation than that of the anchor cable. The anchor cable with the C-shaped tube can reduce the deformation and plastic area of the roadway more effectively. [ABSTRACT FROM AUTHOR]

Rock bursts are a natural phenomenon that are caused by high stresses and faults within the deep geological profile. The framework within deep mining excavations, comprising various rock and face supports such as cable bolts, is required to withstand rock bursts. These mechanisms are subject to static and dynamic loading conditions which possess unique challenges. This study focused on the shearing impact of static loads on cable bolts, a key structural support mechanism designed to absorb energy and investigate the impacts of bolt diameter and strength. A double shear test was modelled using the Finite Element Analysis (FEA) software ABAQUS/Explicit. A double shear test was modelled using Finite Element Modelling (FEM) by creating individual parts, assigning material and contact properties and applying a load directly on the central block. Because ABAQUS/Explicit was used, a primarily dynamic analysis tool, quasi-static loading, was applied to negate the natural time scale. A total of six bolt diameters and six bolt strengths were tested. A positive correlation was exhibited between the bolt diameter, yield strength and the maximum force and displacement. [ABSTRACT FROM AUTHOR]

As rock bursts are unavoidable in deep mines and excavations with high in-situ stresses, ground support systems are implemented to manage and mitigate rock bursts. Cable bolts are commonly used as reinforcing elements in ground support systems, which are subject to dynamic loads in burst-prone excavations. To design an efficient cable bolt in burst-prone conditions, shear and energy absorption capacity must be considered. Numerical modelling is an advantageous method of repeatable testing and it is inexpensive and non-destructive. This study develops a statically and dynamically loaded numerical model of a double shear test in ABAQUS/Explicit. A total of 36 static and 576 dynamic tests are carried out, which examine the influence of bolt diameter, steel yield and ultimate strength, dynamic load velocity and dynamic load mass on the displacement, shear force and energy absorption capacity of cable bolts. As bolt diameter and steel yield strength increases, the maximum shear force resisted and bolt displacement increases. Similarly, as the mass and velocity of the dynamic load increases, the amount of energy absorbed by the cable bolt increases. The main novelty of the current research is to suggest a reliable computational tool to investigate the influence of the different key parameters in the cable bolts on the ultimate capacity. The suggested method is a significantly cost-effective technique compared with the experimental investigations. [ABSTRACT FROM AUTHOR]

In view of the complex asymmetric deformation characteristics of inclined coal seam roadways and the tensed shear failure of anchor cable supports, the asymmetric support scheme of an anchor cable with a C-shaped tube is proposed. In order to study its supporting effect on an inclined coal seam roadway, this paper first explores the difference in shear performance between an anchor cable with a C-shaped tube and an anchor cable through double shear tests. Then, based on the asymmetric deformation characteristics of an inclined coal seam roadway in the Pangpangta Mine, a numerical simulation is used to study the asymmetric support effect of an anchor cable with a C-shaped tube in an inclined coal seam roadway. The results of the double shear test show that the anchor cable with the C-shaped tube has stronger resistance to shear load than that of the anchor cable. Through the results of the numerical simulation, the original stress field distribution on both sides of the roadway was found to be uneven due to the influence of the coal seam dip angle, and after the excavation of the inclined coal seam roadway, the displacement and plastic zone distribution on both sides showed obvious asymmetric characteristics. Compared with the symmetric support, the asymmetric support can obviously alleviate the asymmetric deformation characteristics of the two sides and effectively control the deformation and plastic failure zone of the roadway. The anchor cable with the C-shaped tube has better resistance to shear deformation than that of the anchor cable. The anchor cable with the C-shaped tube can reduce the deformation and plastic area of the roadway more effectively.

The application of geopolymer adhesive to CFRP‐strengthened the RC structure is a new green reinforcement method, and the bonding behavior of geopolymer adhesive was studied in this paper. The geopolymer mechanical properties orthogonal test was conducted and the optimal proportion was obtained, which summarized the influence of slag powder content, liquid–solid ratio, and water glass modulus. A total of 15 adhesively bonded CFRP‐concrete double‐lap joints were fabricated and tested under shear loading to investigate the effect of geopolymer adhesive on the bonding behaviors. Modified bond‐slip models of the geopolymer adhesive specimens were developed and compared with the test date. The results showed that the failure models of epoxy adhesive and geopolymer adhesive are different. The bond strength, interface stiffness, and maximum shear stress of the geopolymer adhesive specimen can reach 93.6% ~ 97.6%, 95.7% ~ 132.9%, and 91% ~ 94% of the bond strength of epoxy adhesive respectively. The predicted τmax and s0 of the proposed model are in excellent agreement with the experimental data, and the maximum deviation is −9.58%. This study proposes that geopolymer could be applied as an effective adhesive in the strengthening of RC structures. [ABSTRACT FROM AUTHOR]

Rock bursts are a natural phenomenon that are caused by high stresses and faults within the deep geological profile. The framework within deep mining excavations, comprising various rock and face supports such as cable bolts, is required to withstand rock bursts. These mechanisms are subject to static and dynamic loading conditions which possess unique challenges. This study focused on the shearing impact of static loads on cable bolts, a key structural support mechanism designed to absorb energy and investigate the impacts of bolt diameter and strength. A double shear test was modelled using the Finite Element Analysis (FEA) software ABAQUS/Explicit. A double shear test was modelled using Finite Element Modelling (FEM) by creating individual parts, assigning material and contact properties and applying a load directly on the central block. Because ABAQUS/Explicit was used, a primarily dynamic analysis tool, quasi-static loading, was applied to negate the natural time scale. A total of six bolt diameters and six bolt strengths were tested. A positive correlation was exhibited between the bolt diameter, yield strength and the maximum force and displacement.

As rock bursts are unavoidable in deep mines and excavations with high in-situ stresses, ground support systems are implemented to manage and mitigate rock bursts. Cable bolts are commonly used as reinforcing elements in ground support systems, which are subject to dynamic loads in burst-prone excavations. To design an efficient cable bolt in burst-prone conditions, shear and energy absorption capacity must be considered. Numerical modelling is an advantageous method of repeatable testing and it is inexpensive and non-destructive. This study develops a statically and dynamically loaded numerical model of a double shear test in ABAQUS/Explicit. A total of 36 static and 576 dynamic tests are carried out, which examine the influence of bolt diameter, steel yield and ultimate strength, dynamic load velocity and dynamic load mass on the displacement, shear force and energy absorption capacity of cable bolts. As bolt diameter and steel yield strength increases, the maximum shear force resisted and bolt displacement increases. Similarly, as the mass and velocity of the dynamic load increases, the amount of energy absorbed by the cable bolt increases. The main novelty of the current research is to suggest a reliable computational tool to investigate the influence of the different key parameters in the cable bolts on the ultimate capacity. The suggested method is a significantly cost-effective technique compared with the experimental investigations.

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Fiber reinforced polymer (FRP) has been widely used as a strengthening material for structures. Hybrid bonding (HB) technique is developed to effectively prevent the FRP debonding in applications. However, researches on the bond behavior with this technique is limited. This study aims to investigate the bond behavior between CFRP and concrete after the HB strengthening. Double shear test was conducted on eight specimens with concrete blocks, CFRP strips, and anchorage. Effects of the bond length and number of plies were considered in the test. Results showed that FRP rupture is the primary failure mode for the CFRP-concrete interface with the HB technique, and anchorage failure will also occur if the shear load at the steel plates is larger than the pull out load of the anchorage. The recommended pull out load of a single anchor set for the HB technique is 14.5 kN. Failure process of the CFRP-concrete interface with HB technique is divided into three stages and the increase of number of plies of CFRP strip effectively increases the load in the third stage. To fully utilize the bond strength of the externally bonded CFRP strip, a recommended spacing of the anchorages is in the range of 0.6 L e to 1.0 L e. Bond strength of the CFRP-concrete interface with HB technique can be well predicted by the proposed models under different bond lengths. • Bond behavior of CFRP-concrete interface was studied using the double shear test. • Effects of bond length and number of plies on bond behavior was studied. • Spacing of the anchorages was recommended. • Pull out load of a single anchor set was recommended. • Analytical models of bond strength and ultimate strength were proposed. [ABSTRACT FROM AUTHOR]

Significant issue in reinforced concrete (RC) structures is corrosion of steel. High alkalization of cement matrix, low permeability, and sufficient cover plays an important role to shield from corrosion of steel. There is a replacement material for steel is fiber‐reinforced polymer (FRP) bars as reinforcement. The FRP bars are nonconductive and durable material and they are composited from fibers and polymers matrix. In this study, new technology geopolymer concrete (GC) was used along with glass fiber‐reinforced polymer (GFRP) and basalt fiber‐reinforced polymer (BFRP) bars. GC is produced from industrial by‐product materials such as fly ash and ground granulated blast furnace slag (rich in silica and alumina) and treated as sustainable material. The long term durability of many RC structures affects drastically by the reinforcement corrosion. Main aspect of bond behavior is tension stiffening as it has capability to control the reinforcement to shift the tensile stresses to concrete. This paper evaluates the bond strength between the GC reinforced with GFRP/BFRP and the results were evaluated with conventional concrete (CC) reinforced with steel. The pullout test method was used to determine the bond between FRP and steel bars with the surrounding concrete based on IS: 2770 (part I)‐1967. The comparison of bond strength GC with FRP almost same as CC with steel. The tension test and double shear test were also carried out in FRP and steel bars based on IS 432–1982 and 5242–1979, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The bond-slip relationship of Carbon Fiber Reinforced Polymer (CFRP) plate-concrete after the influence of high temperature action of Stone Mastic Asphalt (SMA) paving was investigated in this article. Two groups of double shear specimens with different bonding length were designed and tested. Based on the test results, the failure modes of specimens, the strain distribution and the shear stress of CFRP-concrete interface were analyzed. Considering the influence of high temperature, the interfacial bond-slip constitutive model of CFRP plate and concrete after high temperature action of SMA paving construction was proposed. The proposed model can reflect the nonlinearity and interface softening behaviour of the CFRP plate-concrete interface constitutive relationship under special environment. Through the comparative study of exixting constitutive models, the interface bond-slip constitutive model proposed in this paper considers the effect of high temperature and has good agreement with the test results. [ABSTRACT FROM AUTHOR]

Rockbolts are widely used as an underground support element to resist the convergence and maintain the stability of excavations. However, shear failure of rockbolts is increasingly observed in jointed rock mass of underground tunnels, especially after being subjected to seismic events. At present, understanding of the mechanical response of rockbolts subjected to seismic or dynamic loading in shear is still unclear. To investigate the shear performance of rockbolts under dynamic loading condition, a series of tests were conducted using a drop mass of up to185 kg from a maximum height of 3 m based on a double shear test (DST) system. Three variables were examined in the laboratory test including rockbolt diameter (8 mm and 16 mm), installation angle (90° and 45°) and input energy (drop height). The duration of the impact was 10–12 ms from release of the drop mass to first contact. By evaluating the DST system's displacement/velocity/acceleration–time characteristic and the amount of energy absorption, the shear performance of rockbolt was assessed. When sufficient energy is applied into the DST system, the deformation of the rockbolt is dominated by localized shear force. The transient force can rupture the rockbolt with little bending and without any obvious tensile elongation. It was found that the averaged dynamic shear load is less than the peak static shear load whether horizontally installed or installed at an angle. In conclusion, the effectiveness of rockbolts in resisting shear stress can differ significantly under static loading and dynamic loading condition; the difference is reflected in the level of shear deformation and amount of energy absorption. The shear capacity of a rockbolt under 1 s−1 strain rate can be determined by the energy absorbed and average dynamic load. This approach can be applied to the support system design in rockburst-prone condition. [ABSTRACT FROM AUTHOR]

Rockbolts have been used to minimize the deformation of underground excavations where the surrounding rock masses contain weak planes such as fractures, joints or faults. Rockbolts installed across rock joints are able to resist the opening and shearing movements of rock joints. One of the rockbolt failure modes encountered in the field is caused by the excessive shear loads. A simple analytical model based on the Beam on Elastic Foundation (BEM) method is proposed in this study to predict the shear responses of a bolt installed perpendicularly to rock joint. The shear load-displacement curve of a double shear test can be divided into three stages: the elastic stage, the elasto-plastic stage and the plastic stage. The foundation stiffness for each respective stage are varied with the curvature influencing zone L c . The pretension effects are taken into account in the proposed analytical model. The model agrees well with the experimental shear tests, suggesting that the analytical model has the capability to predict the shear load-displacement curve of bolts crossing rock joints. [ABSTRACT FROM AUTHOR]

The application of cable bolts as a secondary support system is an increasing trend in underground coal mines worldwide. The performances of cable bolts have been evaluated under both axial and shear loading conditions. Two methods of testing cables for shear, single and double shear, have been recognised. This paper examines the shear behaviour of a variety of cable bolts under different pre-tension loads by double shear testing. Plain, spiral and the combination of both cable types were used in this study. The initial axial load and the type of cable bolts are the main factors affecting their shear strength. By increasing the axial pre-tension load, the peak shear load occurs at lower shear displacement. The failure angle due to cable bending across the joint at different pre-tension loads varied between 41° and 49°. This demonstrates that the ratio of axial and perpendicular displacements is almost constant and on average the failure occurs at about 45°. A novel analytical model is proposed to evaluate the shear behaviour of pre-tensioned fully grouted cable bolts subjected to double shearing. Energy and Fourier Series methods were incorporated in the model to simulate the shear behaviour of cable bolts. The comparison of the experimental results with the proposed model shows a good agreement. [ABSTRACT FROM AUTHOR]

This paper focuses on the bonding performance of the interface between fiber-reinforced polymer (FRP) profiles and concrete. The bond shear capacity and the bond shear strength of the wet-bond (WB) interface, the shear-key (SK) interface, and the shear-key combined with wet-bond (SK-WB) interface were investigated via double-lap push shear tests with 15 specimens. Varying numbers of shear keys were adopted in the SK and SK-WB specimens to study the influence of the bonding area of the shear keys. The slip between the FRP profiles and the concrete was measured, and the bond stresses at different points of the test zone were calculated with differential operations. The results show that the average bond strength and the maximum slip of the SK-WB interface are significantly higher than those of the SK interface, whereas the average bond strength and maximum slip of the SK interface are significantly higher than those of the WB interface. A much greater concentration of stress was discovered in the SK interface compared with the SK-WB interface. The capacity load value and the maximum slip value of the double-SK interface are higher than those same values of the single-SK interface. The comparison of bond strength was performed between the FRP profiles-concrete interface and the FRP plate-concrete interface. The results show that the bond strength of the WB interface between the concrete and the FRP profile by the double-lap push shear method is much lower than the bond strength of the WB interface between the concrete and the FRP plate when using the double-lap pull shear method. Finally, the significant difference in the bond strengths is explained using the stress analysis method. [ABSTRACT FROM AUTHOR]

A new series of double shear tests were carried out using a newly modified double shear apparatus which prevented contacts between concrete block surfaces during shearing. 13 double shear tests were carried out using 21 mm diameter 19 (9 × 9 × 1) seal construction wire strand cable (also called Superstrand cable), Plain SUMO, Indented SUMO, Spiral MW9 and Plain MW10 cable bolts. These cables were tested subjected to different pretension loads. Concrete blocks with Uniaxial Compressive Strength (UCS) of 40 MPa and Stratabinder grout were used for all the tests to maintain test consistency. The results show that the peak shear load and the corresponding shear displacement decrease by increasing the pretension load of the tested cable. The Ultimate tensile strength, lay length, number of wires and cable bolt surface profile type (plain and spiral/indented) are important factors in total shear strength of the cable bolt. [ABSTRACT FROM AUTHOR]

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The shear performance of cable bolt is important in assessing its load transfer capacity for effective rock strata reinforcement, which has not yet been thoroughly investigated and understood. Tests carried out in laboratory to study the cable shear performance can be simply classified into two types, the Single Shear Test (SST) and the Double Shear Test (DST). A variety of single and double shear test apparatuses developed in the past were reviewed and the main controlling factors when designing a new shear test apparatus were concluded based on the existing shear test apparatuses and their application. Four cable bolts were tested in laboratory conditions using the DST apparatus developed in the University of Wollongong, the British Standard Single Shear Test apparatus (BSST) and the Megabolt Single Shear Test apparatus (MSST) to compare and assess these different shear test apparatuses. Test results showed that the MSST results were completely different from the BSST results but similar to the DST results. Cable bolts tested in BSST tended to fail at small shear force and shear displacement in the form of inclined shear failure surfaces, whilst cable bolts installed in MSST and DST both tended to fail at greater shear force and shear displacement in the form of tensile cone and cup with bending deformation. It is concluded that both single and double shear test methods can effectively assess cable bolt shear performance as long as suitable apparatus dimensions and boundary conditions are used. [ABSTRACT FROM AUTHOR]

In this work, we propose Bayesian parameter estimation of a nonlinear mechanics based model describing the behaviour of mortar subjected to double shear test with externally bonded carbon fibre reinforced polymer (CFRP) plates. With the Bayesian approach, it is possible to identify mechanical material parameters of different phases of the mortar mesostructure, i.e. hardened cement paste, aggregates and interface transition zone (ITZ). Due to nonlinearity of the concerned problem, we use a novel sequential approach for the parameter inference, which does not require coupling between the finite element solver and software for the stochastic analysis. The model geometry and material mesostructure are learned based on micro-computed tomography (μ CT) scans of the real specimen, whereas the unknown boundary conditions are assumed to be uncertain and are also identified from experimental data. Mortar is modelled through a discrete lattice model consisting of spatial Timoshenko beams with embedded discontinuities. The latter allows the description of the distinct stages in material degradation, from the appearance of microscopic material damage to its evolution into macroscopic cracks leading to localised failure. • Elastic and fracture meso-parameters of mortar are inferred using Bayesian approach. • Boundary and loading conditions are hard to reproduce and considered as uncertain. • Novel sequential approach decouples finite element and stochastic computations. • Geometry and material mesostructure are learned from micro-CT scans of the specimen. • Observations of surface displacements are acquired by digital image correlation. [ABSTRACT FROM AUTHOR]

Failure of rockbolts as a result of shear or bending loads can often be found in underground excavations. The response of rock anchorage systems has been studied in shear, both by laboratory tests as well as numerical modelling in this study. A double shear test was developed to examine the shear behaviour of a bolt installed across two joints at different angles. To investigate the influence of various parameters in the double shear test, a numerical model of a fully grouted rockbolt installed in concrete was constructed and analysed using FLAC3D code. A number of parameters were considered including concrete strength, inclination between rockbolt and joints and rockbolt diameter. The numerical model considered three material types (steel, grout and concrete) and three interfaces (concrete-concrete, grout-concrete and grout-rockbolt). The main conclusions drawn from the study were that the level of bolt resistance to shear was influenced by rock strength, inclination angle, and diameter of the rockbolt. The numerical simulation of the bolt/grout interaction and deformational behaviour was found to be in close agreement with earlier experimental test results. [ABSTRACT FROM AUTHOR]

The columns of monumental buildings in ancient Greece were provided with a pair of timber “empolia” (plugs) and a “pole” (pin), at interfaces between stone members (drums, capital). In order to reinstate this connection system, in columns capitals that were repaired, during the ongoing restoration of the classical temple of Apollo Epikourios (Greece), new poles and empolia made of titanium were installed. The titanium elements were designed to have similar shape and shear strength to the estimated respective characteristics of the ancient poles and empolia. Moreover, their effect on the seismic behaviour of the temple columns was numerically investigated. The investigation showed that, within the range of strong earthquakes which are anticipated in the area of the monument, the installation of a single pole at the interface between the capital and the uppermost drum leads to limited reduction of the expected maximum and residual deformations of the column, without altering significantly the main characteristics of its rocking response. Furthermore, poles located at every column interface ensures significant limitation of the column residual deformations. Prior to implementation of the titanium poles and empolia, the main aspects of their design were verified through specially designed experiments. [ABSTRACT FROM AUTHOR]

The use of carbon fibre reinforced polymer (CFRP) tendons instead of steel tendons is a promising method for improving the overall performance of beam string structures. However, research on the shear behaviour of CFRP tendons is insufficient. In this paper, the effect of chamfering of the cable clamp plate used in the connected joint between prestressed tendons and struts for beam string structures on the shear behaviour of CFRP tendons was analyzed. The transverse shear tests were conducted on 5-mm-, 7-mm- and 9-mm-diameter transverse enhanced CFRP tendons to investigate the effect of chamfering. Experimental results show that the chamfering increased the transverse shear strength of 7-mm-diameter CFRP tendons significantly (approximately 15%) and slightly (approximately 0–3%) improved the shear strength of the 5-mm- and 9-mm-diameter tendons. The transverse shear deformation of the three diameters of CFRP tendons increased by 35%, 77% and 92% compared with no chamfering effect. Another important result is that the mechanical mechanism and failure mode of shear plane for all specimens were changed by the chamfering. Complete cross-section fracture on the shear plane of CFRP tendons has not occurred, and the tendons can still have some transverse bearing capacity after shear failure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experiment on the interface performance between implantable cement-based sensor and matrix concrete was conducted. • The main four interface failure modes and three failure appearances were observed and analyzed. • The bonding between the coated sensor and the matrix concrete is enhanced through grooving the coated surface. • Bond-slip model between implantable cement-based sensor and matrix concrete under different interface conditions was suggested. • The smaller the strength difference between cement-based sensor and the matrix concrete is, the better the coordination and coupling performance of the interface can be guaranteed. Design and manufacturing the implantable cement-based sensor have attracted more and more attentions in the field of the concrete infrastructure health monitoring due to the mechanical and deformational integrity feature between the cement-based sensor and the infrastructure. The good coupling through the interface between the implantable cement-based sensor and the matrix concrete is the key to maintain such integrity to achieve the long-term and accurate health monitoring. A new interface double shear test device is designed and manufactured in this study to investigate the interface behavior between the implantable cement-based sensor and the matrix concrete. The measurement on the interface bond-slip performance is conducted considering the factors such as the water-to-cement ratio of the matrix concrete, whether the sensor surface is coated/grooved or not, the coating thickness, the grooving depth. The experimental results of the load-slip curve, the shear strength, and the failure mode are analyzed to reveal the shear bonding mechanism and to establish the interface bond-slip model for the implantable cement-based sensor and the matrix concrete. The findings of this study can benefit the interface design and manufacturing of the implantable cement-based sensors to achieve good cooperative working relationship with the surrounding structures for long-term and accurate monitoring the infrastructures. [ABSTRACT FROM AUTHOR]

Direct bonding is of particular interest for optical system manufacturing for spatial application. This technology is already used in terrestrial optical system manufacturing because of the very high precision of the process and complex geometries are able to bond. However, even if a first prototype already passed with success space environment test, quantification and improvement of the mechanical strength of assemblies are essential to validate the assembly’s life expectancy and to validate the European Space Agency standards. So, this work proposes to study the influence of process parameters, such as roughness, relative air humidity during room temperature bonding, annealing time and temperature, on mechanical strength of an elementary mechanical structure using a double shear test procedure and cleavage tests. At the same time, the performances of fused silica and Zerodur®glasses are compared. For the process considered in this study, a parallel is made between chemical phenomena, surface roughness and mechanical strength. In the end, cleavage tests confirm the choice of the optimal process parameters and highlight a damaging phenomenon of bonded interfaces with successive re-adhesion. [ABSTRACT FROM AUTHOR]

Abstract: Timber frame construction with earth brick infill is a sustainable design that is promising in the building construction field. However, cracks form at the interfaces of the bricks and frame with temperature and humidity fluctuations. A geopolymer binder can create stronger bonds between these two materials than traditional mortar, potentially preventing crack formation. This study focuses on the pull-out and shear mechanical behavior of laboratory assemblies of wood, geomaterial binder and two different types of earth brick. The full-field displacements of double-shear test samples were also obtained by digital image correlation (DIC) to better describe and understand the mechanical behavior of the system. The results show that the geopolymer binder provides good adhesion of approximately 1.5MPa or 2MPa, depending on the type of brick. Failure localization is also different for each assembly, occurring inside the brick and binder or only inside the binder. This result is confirmed by DIC analysis. The microstructure of the brick has been correlated with the mechanical behavior of the assembly. First results show that the geopolymer binder can be used as a joint in wood and earth masonry. [Copyright &y& Elsevier]

Abstract: In building construction, because of the hygroscopic nature of wood and earth brick and the low adhesion between these materials, cracks are formed at their interface when they are assembled. Geopolymer binder has been show to create strong bonds between wood and earth brick. Assemblies of wood and extruded earth brick with geopolymer binder were manufacture and tested. Double shear tests at two scales were carried out that provided evidence of good adhesion and information about the influence of the type of brick on shear behavior. The workability of the binder was improved by adding siliceous aggregates. The mortar obtained has an improved compressive strength, ranging from 3 to 8MPa, depending on the aggregate size. FTIR measurements and thermal analysis were performed to determine the reaction mechanism. [Copyright &y& Elsevier]

The article explores an experimental study of bond between carbon fiber reinforced polymeric (CFRP) plates and concrete that are both essential in shear and flexural applications. The study involves the testing of concrete specimens strengthened with different types of carbon fiber reinforced polymeric (CFRP) plates that are subject to double shear test. The results of the study offer an adequate characterization of the interfacial region on bond strength as well as the types of failure.

Abstract: This paper focuses on investigating the bonding fatigue performance between two asphalt concrete (AC) layers. For purposes of this experimental campaign, a customised double shear testing device was designed. Two interface conditions have been analysed herein: with and without a tack coat. Moreover, the corresponding fatigue behaviour has been analysed at two temperatures: 10°C and 20°C. As expected, the absence of a tack coat leads to a decrease in bonding fatigue performance. Since fatigue tests are highly time-consuming, a method that allows predicting the conventional interface fatigue law from accelerated shear fatigue tests has been proposed. Other novel findings on interface fatigue behaviour will also be discussed. In addition to these fatigue results, an interface failure model is proposed to evaluate the interface lifetime. Incorporating interface fatigue performance into pavement analysis proves to be a key parameter in describing in situ pavement conditions and assessing pavement durability. [ABSTRACT FROM AUTHOR]