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Rock bolting technique is an important reinforcement measure in the geotechnical engineering practice. New rock bolts have been continuously emerging through the development of rock supporting technology. Complex conditions, such as high crustal stress, extremely soft rock, and strong mining disturbance often occur in the deep mining, resulting in large deformation of the surrounding rock masses. Since the deformation of traditional rock bolts is generally below 200 mm, failure often occurs to the rock bolts because of insufficient deformability. To effectively control the large deformation of surrounding rock masses caused by complex conditions, it is necessary to develop large deformation rock bolts with high constant resistance, also called energy-absorbing bolts. This paper systematically reviews the development of large deformation rock bolts and the structure, energy absorption mechanism, anchorage performance, and mechanical properties of several typical large deformation rock bolts. The advantages and disadvantages of existing large deformation rock bolts are compared and the concept of constant resistance large deformation support is introduced. [ABSTRACT FROM AUTHOR]

In suspension bridges, cable anchorage system is the critical structure for cable tension transmission. For traditional rear anchor girder anchorage system and pre-stressed anchorage system, problems such as local compression and inconvenient construction are inevitable. This paper presents the development of a novel PBL anchorage system used in the 4th Nanjing Yangtze River Bridge. This PBL anchorage system adopted grouped perfobond rib shear connectors (known as PBL shear connectors) in the independent perforated steel plate. Two full-scale specimens were extracted from the practical design. The load–slip curves and the strain developments were obtained. The results revealed the reliable load-carrying capacity and very slight residual slip after the cyclic unloading from the design load. The load carried by each row of PBL shear connectors proved the distributed load-carrying capacity. Finite-element analyses were conducted in ANSYS, which agreed well with the test results. Further parametric analyses focusing on the spacing and rows of PBL shear connectors were conducted. Based on the analysis results, the design methods of the PBL anchorage system were suggested. [ABSTRACT FROM AUTHOR]

The stability of tunnel-type anchorages is related to the stratum lithology and geological conditions of the anchorage sites. The bearing behavior of tunnel-type anchorages in soft rock with underlying weak interlayers is analyzed in this work using a field model test. Using FLAC3D, we investigate the effects of the geometric parameters (i.e., base angle, β, length, L) of plug bodies and the distance, D, between the right and left plug bodies on the stress states of weak interlayers. The results show four stages of surrounding rock deformation. Furthermore, the vertical displacement of the surrounding rock is less than that in the main cable force direction. In dealing with tunnel-type anchorages in soft rock with underlying weak interlayers, focus should be directed towards controlling the surrounding rock deformation in the main cable force direction. The surrounding rock in the postmedian plug body is the main bearing part of a tunnel-type anchorage. The final failure mode of tunnel-type anchorages in soft rock with underlying weak interlayers is similar to that of an inverted wedge body. Moreover, this final failure mode is slightly related to the plug body's geometric parameters and the distance between the right and left plug bodies. The maximum tensile stress, tmax, inside the weak interlayer decreases as the distance, D, between two plug bodies (or length, L) increases, and it increases as the base angle, β, of the plug body increases. The parameter sensitivity of the plug body to tmax is ranked as β > L > D. [ABSTRACT FROM AUTHOR]

Summary: In recent earthquakes in developing countries, severe damage was observed on reinforced concrete buildings. This study focuses on exterior beam‐column joints with substandard beam rebar anchorage and seismic strengthening by installing wing walls. First, a series of experiments was conducted to investigate the seismic behavior of exterior joints with substandard beam rebar anchorage representing typical Bangladeshi buildings. Two 0.7‐scaled exterior joint specimens were tested, and these specimens showed beam rebar anchorage failure and/or joint shear failure. Prior to strengthening of the joint, a series of pullout tests was conducted on postinstalled bonded anchors in low‐strength concrete for strengthening design. Then, an experiment was performed to apply the strengthening method by wing walls to one of the exterior joint specimens to improve the integrity, and this method was intended to prevent the failure of beam rebar anchorage. The strengthening method is proposed to extend the development length of beam longitudinal bars by considering the embedment length along the wing walls. The test results verified the effectiveness and applicability of the proposed strengthening method to upgrade exterior RC beam‐column joints with deficient beam rebar anchorage. [ABSTRACT FROM AUTHOR]

Red clay is a special soil layer with complex engineering properties distributed in tropical and subtropical regions. An anchor cable support is a common form of red clay slope support. The effectiveness of the anchor cable support is mainly determined by the anchoring force provided by the red clay stratum. Increase of the water content will lead to the rapid deterioration of the mechanical properties of red clay, which will lead to the reduction of the anchoring force of the slope anchor cable and lead to the failure of the support. Based on the classical Phillips and uniform anchorage shear stress distribution theory, this paper puts forward a uniform-exponential distribution pattern of anchorage shear stress according to the specific characteristics of red clay by using the characteristics of the peak shear strength and residual shear strength of the rock and soil mass. With increasing anchorage force, the dynamic evolution (single exponential distribution ⟶ double single exponential distribution ⟶ uniform index exponential complex distribution ⟶ uniform distribution) of the anchorage shear stress is analysed. Based on the peak and residual test of the cohesive force and internal friction angle, the relationship between the anchoring force and buried depth and water content is established by analysing the factors influencing the anchoring force. It can be found from the field test that, according to the relationship established, the limit anchorage force of the anchor cable in the red clay stratum can be calculated and the water sensitivity of the anchor cable's limit anchorage force can be quantitatively analysed. [ABSTRACT FROM AUTHOR]

This paper proposes a theoretical solution for predicting the pullout properties of a single fiber-reinforced polymer (FRP) rod embedded in a bond type anchorage based on a trilinear bond–slip model. The radial variation of the shear stress and reaction of the steel sleeve are considered in the solution. Pullout procedure with elastic, elastic-softening, elastic-softening-debonding, pure softening, softening-debonding, and debonding stages, as well as the corresponding critical stages, are analyzed. In this theoretical solution, the maximum pullout load, shear stress along the rod–grout interface, axial tensile stress of the FRP rod, and load–slip relationship are derived with explicit formulations. Effective bond length of bond type anchorage is also discussed. The solution is validated against experimental results available in literature. The theoretical solution reveals that the anchorage may attain its maximum pullout load in the elastic-softening, pure softening, or elastic-softening-debonding stage. Moreover, the effects of embedded length, ultimate shear stress, and residual shear stress on maximum pullout load closely related with the stage in which the anchorage attains its maximum pullout load. However, the effect of radius of FRP rod on the maximum pullout load increases with the embedded length, no matter in which stage the anchorage attains its maximum pullout load. [ABSTRACT FROM AUTHOR]

Three large-scale connections between square concrete-filled steel tubular (CFST) columns and H-section steel beams were tested. T-shaped vertical anchorage was used as the embedded elements and both static and seismic behaviours of the connections were tested in this study. The experimental parameters include length and location of T-shaped vertical anchorage. Based on the experimental data, the strength, ductility, stiffness degradation, and energy dissipation of the connections were calculated. The test results show that the connections exhibit good static and seismic behaviours. Furthermore, a parametric study was conducted using the finite element method where the considered parameters include the height and depth of end anchorage, and the thickness of vertical plate. Based on the study results, a preliminary design method is proposed, which includes the design formulae for calculating the thickness of vertical plate, the thickness of end anchorage, and the punching shear capacity of concrete. In conclusion, with a proper design, the connections with T-shaped vertical anchorage can be reliably used in practical applications. [ABSTRACT FROM AUTHOR]

The length of anchorage zone of an anchor bolt affects the distribution of axial force and shear stress therein. Based on a shear–displacement model, the load distribution of anchor bolts in the elastic deformation stage was analysed. Moreover, the mechanical response of threaded steel anchor bolts with different anchorage lengths was explored through pull-out test and numerical simulation. The results showed that axial force and shear stress were negatively exponentially distributed within the anchorage zone of anchor bolts in which there were the maximum axial force and shear stress at the beginning of the anchorage zone. In the elastic deformation stage of the anchorage, the longer the anchorage length, the more uniformly the shear stress was distributed within the anchorage zone and the larger the ultimate shear stress; however, there was a critical anchorage length, which, when exceeded, the ultimate shear stress remained unchanged. The calculation formula for the critical anchorage length was deduced and a reasonable anchorage length determined. The research result provides an important theoretical basis for rapid design of support parameters for anchor bolts. [ABSTRACT FROM AUTHOR]

Nanfen open-pit iron mine is the largest single open-pit mine in Asia. Because of the lag of the extension project, the section has slowly spread in the shape of "V," and disasters such as landslides occur frequently. In this study, first, the NPR anchor cable monitoring, which shows supernormal mechanical characteristics and can realize the monitoring and early warning target for the whole landslide process and early warning curve of bedding rock "2016-1101 landslide" in the lower wall of Nanfen open-pit mine, was analyzed, revealing the failure process of the bedding rock landslide and the force evolution characteristics of the NPR anchor cable. Then, based on the Fish language in FLAC3D and 3DEC software, the mechanical model of the NPR anchor cable was constructed, and numerical simulation was performed on the whole process of "16-1101 landslide" induced by accumulation of old landslide body. The results of this study indicate that the stress monitoring curves and failure characteristics of the NPR anchor cables in the whole process of landslide by the two numerical simulation methods are basically consistent with the field measurement results, providing a theoretical and practical basis for the mechanistic analysis and numerical simulation of other similar slopes. [ABSTRACT FROM AUTHOR]

The yeast cell surface provides space to display functional proteins. Heterologous proteins can be covalently anchored to the yeast cell wall by fusing them with the anchoring domain of glycosylphosphatidylinositol (GPI)-anchored cell wall proteins (GPI-CWPs). In the yeast cell-surface display system, the anchorage position of the target protein in the cell wall is an important factor that maximizes the capabilities of engineered yeast cells because the yeast cell wall consists of a 100- to 200-nm-thick microfibrillar array of glucan chains. However, knowledge is limited regarding the anchorage position of GPI-attached proteins in the yeast cell wall. Here, we report a comparative study on the effect of GPI-anchoring domain–heterologous protein fusions on yeast cell wall localization. GPI-anchoring domains derived from well-characterized GPI-CWPs, namely Sed1p and Sag1p, were used for the cell-surface display of heterologous proteins in the yeast Saccharomyces cerevisiae. Immunoelectron-microscopic analysis of enhanced green fluorescent protein (eGFP)-displaying cells revealed that the anchorage position of the GPI-attached protein in the cell wall could be controlled by changing the fused anchoring domain. eGFP fused with the Sed1-anchoring domain predominantly localized to the external surface of the cell wall, whereas the anchorage position of eGFP fused with the Sag1-anchoring domain was mainly inside the cell wall. We also demonstrate the application of the anchorage position control technique to improve the cellulolytic ability of cellulase-displaying yeast. The ethanol titer during the simultaneous saccharification and fermentation of hydrothermally-processed rice straw was improved by 30% after repositioning the exo- and endo-cellulases using Sed1- and Sag1-anchor domains. This novel anchorage position control strategy will enable the efficient utilization of the cell wall space in various fields of yeast cell-surface display technology. Image 1 • The GPI-anchoring domain fused with a heterologous protein determines its anchorage position in yeast cell wall. • Proteins fused with the Sed1-anchoring domain predominantly localize to the external surface of the cell wall. • The anchorage position of proteins fused with the Sag1-anchoring domain is mainly inside of the cell wall. • By repositioning EG and BGL in yeast cell wall, the ethanol titer from pretreated rice straw was improved by 30%. [ABSTRACT FROM AUTHOR]

This paper presents the feasibility and effectiveness of an alternative anchor system for reinforced concrete beams strengthened with carbon fiber-reinforced polymer (CFRP) sheets. Continuum U-wrap anchors that enclose the longitudinal CFRP sheets are conventionally employed to impede the premature delamination of the sheets. This method, however, is not cost-effective and completely blocks the bonded region, thereby disrupting any technical maintenance and visual inspections on the shear span of the beam. Grid CFRP U-wraps are proposed to address these concerns. Twenty beams are tested to examine the effects of the following parameters: anchorage types (continuum and grid U-wraps), grid configurations, shear-span coverage ratios (25 to 100%), bonding schemes (epoxy and silyl-modified polymer [SMP] adhesives), and loading conditions (monotonic and cyclic). Of interest are the flexural capacity of the strengthened beams, failure modes and crack propagation, and strain development that represents the behavior of the CFRP-concrete interface. The grid U-wraps alter the failure characteristics of the beams in conjunction with the interrupted formation of diagonal tension cracks. The use of SMP alleviates stress concentrations at the beam corners, preserving the integrity of the grid U-wraps. Cyclic loading brings about the progressive shearing of the CFRP sheet; accordingly, the capacity of the strengthened beams decreases. When SMP-epoxy hybrid bonding is used, the grid U-wraps result in flexural responses comparable with those of their continuum counterparts. Statistical inference techniques clarify the relationship between the anchorage configuration and the coverage ratio. [ABSTRACT FROM AUTHOR]

A mechanical model for anchorage and surrounding rock was established against the failure of bolting system, the differential equation of load-transfer was solved and the shape and depth of excavation damaged zone (EDZ) of the surrounding rock was analysed. The results show that to achieve full performance of rockbolts materials and to lengthen its service life, two requirements must be met. One is that the load of rockbolt is no more than its load-bearing capacity. The other one is that the anchorage should be located in stable elastic zone. The shape of EDZ is determined by the magnitude and direction of in-situ stress. Reasonable bolting design should abandon the traditional design of uniform support strength. Rather, should adopt coordinated support and nonuniform support design according to the shape of EDZ in field. Based on the above principles, a new type of combination rockbolt with the effect of high resistance and yield pattern was adopted for the new bolting scheme in the main roadway of Puhe Coal Mine. By analyzing the data collected in field, it is concluded that the combination rockbolt can solve the problem that appearing pull-out failure of rockbolts and tensile failure of cablebolts. [ABSTRACT FROM AUTHOR]

Helical anchors have been used to carry tension loads in different applications including transmission tower foundation, pipeline anchors, foundation repair elements, and excavation bracing. There have been numerous changes in the shape and size of helical anchors and piles since their first usage. Several researchers have studied their failure mechanism to find their pullout capacity. In this paper, the uplift capacity of helical screw anchors has been investigated through laboratory testing. Half-cut double-helix anchors were tested in a sand tank by varying helix size, helix spacing, and relative density of sand. A series of images were captured during the process of anchor pullout. The images were used to obtain displacement and strain fields by Particle Image Velocimetry (PIV). Load–displacement curves have been presented and compared to the earlier works. Afterwards, pullout capacity factors were calculated from peak load values. PIV analysis results were used to study the effects of helix spacing, helix size, and relative density of sand on the displacement fields. The results showed that the effect of helix spacing and soil density in increasing pullout load is more than that of helix size. Moreover, failure surfaces were discussed through displacement and strain fields. The findings indicated that failure surface above the top helix of deeply embedded anchors is a truncated cone with the angle of approximately ϕ 3 , with the vertical and the failure surface shape between the two helices dependent on helix spacing. [ABSTRACT FROM AUTHOR]

Rockbolts can be divided into three types based on the anchorage mechanism - mechanical bolts, bonded bolts and friction bolts (Hoek et al. [7]). A dense and hard grout forms between the bolt and the borehole wall due to the constraint of the borehole wall and the ends of the roll, generating high expansion pressure between the borehole wall and the bolt. High friction between the expanded roll and the borehole wall provides anchorage force to the bolt, which allows the bolt to fulfil the function of controlling rock mass deformation and preventing rock mass failure. The laboratory test results indicate that tensile fracture of the SSAB occurs if the self-swelling roll length exceeds 60 cm. In this case, the ultimate load of the SSAB depends on the ultimate tensile strength of the bolt. [Extracted from the article]

The recent surge of interest towards the mechanical response of rock mass produced by tunnel-type anchorage (TTA) has generated a handful of theories and an array of empirical explorations on the topic. However, none of these have attempted to arrange the existing achievements in a systematic way. The present work puts forward an integrative framework laid out over three levels of explanation and practical approach, mechanical behavior, and calculation method of the ultimate pullout force to compare and integrate the existing findings in a meaningful way. First, it reviews the application of TTA in China and analyzes its future development trend. Then, it summarizes the research results of TTA in terms of load transfer characteristics, deformation characteristics, failure modes, and calculation of ultimate uplift resistance. Finally, it introduces four field model tests in soft rock (mainly mudstone formations), and some research results are obtained. Furthermore, it compares the mechanical behavior of TTA in hard rock strata and soft rock strata, highlighting the main factors affecting the stability of TTA in soft rock formation. This paper proposes a series of focused topics for future investigation that would allow deconstruction of the drivers and constraints of the development of TTA. [ABSTRACT FROM AUTHOR]

The cable-pylon anchorage zone is a typical D-region in a cable-stayed bridge, for which there has been no uniform simplified design method until now. In this paper, based on the extensive statistics of actual projects, topology optimization techniques and principle of minimum strain energy, two precise strut-and-tie models for the cable-pylon anchorage zone are proposed, which can clearly reveal the load-transmitting mechanism of the anchorage zone. Th e explicit geometric parameters of the strut-and-tie models are derived; thus, the designers can directly use these models. A simple design procedure to deploy prestressing tendons in the anchorage zone is also introduced, whose effectiveness and convenience are demonstrated by two design examples. A new design named the "one-way prestressing tendons PC cable-pylon" is also discussed regarding its application scope. [ABSTRACT FROM AUTHOR]

In this paper, pull-out tests of bolt are carried out to investigate the relation between water inflow and bolt-resin interface. Then, water intrusion tests and ring shear tests are sequentially conducted on rock-like specimens to investigate the effects of moisture content on the shear bond strength and failure mode of the rock–resin interface. The results suggest that the shear bond strength is markedly affected by water and failure concentrates on the interface between rock and resin after immersion in water. When comparing shear tests results from specimens with different immersion methods, it is evident that the resins have low hydroscopic behavior. It is also evident that rock weakening after water intrusion is the main cause of shear bond strength reduction of the rock–resin interface. During the failure process of dry specimens, there is evidence of a resin bearing stage, a breaking point and a residual stage that dissipates. Also, the applied load plunges after peak stress is achieved in specimens with increasing moisture content. • the failure of the anchors - anchoring agents - rock interfaces. • the effect of water on anchors. • the effect of water on rock. [ABSTRACT FROM AUTHOR]

Based on the analysis of bending damage of roadway roof, a design method of roof bolting support by using anchorage potential design method is put forward. The method is then applied to numerical simulation of roadway anchorage parameters and support effect. The effect of numerical simulation on supporting schemes was verified through laboratory tests, and the optimal support scheme for roadway was determined. Field test results show that roadway deformation from roof to floor in the optimal support scheme is 210 mm, which is within the control range. The anchorage forces of bolts and cables are within reasonable load coordination and prestress coordination area and roadway stability is good. The amount of bolting material for roadway roof is reduced by 20% compared with the traditional design. [ABSTRACT FROM AUTHOR]

For prestressed carbon fiber reinforced polymer (CFRP) tendon anchorage systems to become well established and used on a large scale, practical requirements for structure strengthening may be met by performing a relatively easy anchorage technique using prestressing CFRP laminates. From testing performed on a clip-type CFRP laminate anchorage system developed in our research group, it was revealed that this system could achieve the anchorage efficiency and the relaxation met the requirement of specification. Furthermore, the relevant indices of the anchorage system met the prestressed system standards. A test on the load-carrying capacity of a full-scale model beam demonstrated that the load-carrying capacity of the beam increased by more than 60% after it was strengthened with the anchorage system. The prestressing CFRP laminates and the bridge structure deformed and bore stress as a composite and exhibited excellent operating performance when working together. [ABSTRACT FROM AUTHOR]

In recent days, many structures are strengthened with fiber-reinforced polymer to make use of the existing reinforced concrete structures to the current needs. Although investigations on the behavior of undamaged fiber-reinforced polymer-strengthened reinforced concrete beams anchored with U-strips have been conducted, study on the behavior of RC box beams strengthened with basalt fiber-reinforced polymer using end anchorage with grooving is still lacking. In the present study, the failure mode, ductility, stiffness, and loading-carrying capacity of an RC box beam strengthened with basalt fiber-reinforced polymer using end anchorage with grooving were experimentally and analytically investigated. Test results and analysis showed that: (1) the average crack spacing, average crack depth, and average crack width of specimen anchored with grooving decreased by 10.3%, 2.8%, and 6.2% when compared with that of specimen anchored with U-strips, respectively; (2) the failure mode of specimen anchored with grooving was basalt fiber-reinforced polymer debonding in pure bending zone; (3) the deflection or curvature ductility of specimen anchored with grooving was 33.9% or 32.7% lower than that of specimen anchored with U-strips; (4) a model based on built-up bars for the load-carrying capacities of BFRP-strengthened beams anchored with grooving was proposed. [ABSTRACT FROM AUTHOR]

Series of constant amplitude fatigue loading tests were carried out on two types of CFRP tendon bonded anchorage systems. The influence of load ratio on fatigue response was investigated by backside strain technology. The prediction model of fatigue damage for the systems with constant amplitude load was deduced based on Goodman equation. The effect of load ratio on fatigue behavior of bonded anchors was investigated by experimental and numerical approaches. The results show that the prediction data are in good agreement with the experimental data. The change of back strain in the fatigue process of bonded anchorage system can well reflect the fatigue damage in the anchorage system, which proves that the back strain gauge technology is suitable for the bonded anchorage system. The fatigue damage model based on backside strain technology can reasonably simulate the effect of load ratio on fatigue response of bonded anchorage systems. [ABSTRACT FROM AUTHOR]

A new anchorage system is proposed having a circular bearing plate and curvature between the bearing plate and the anchor head to improve stress concentration. A lid with a screw instead of the grouting method is also proposed to prevent moisture penetration. The details of the anchorage device have been chosen to reduce stress concentration based on the finite element analysis. Static load test, load transfer test, and hydrostatic test of fabricated devices were carried out according to ETAG 013 to evaluate the proposed design. As results, the anchorage slip and stabilization satisfied the recommendations of ETAG 013. The maximum load in the load transfer test was at least 1.1 times the ultimate tendon strength. The results of the hydrostatic test showed that the developed anchorage device is watertight to protect against corrosion. As a result of bursting force test, it was confirmed that the proposed anchorage device has more advantages than the conventional rectangular anchorage devices in terms of stress distribution. [ABSTRACT FROM AUTHOR]

The contribution of CFRP wraps, as an anchorage system, to enhancing bond behavior between CFRP sheet and cracked concrete, was investigated. Thirty six concrete blocks (150 x 150 x 200 mm) were cast with 3Φ12 mm steel bars embedded laterally at different spacing along the 200-mm-dimension. Half of theΦmoist-cured blocks were subjected to a cyclic treatment in 3% chloride solution until reinforced sides cracked at an average global crack size 0.54 mm; the remaining ones were immersed in a lime solution for a similar period, as controls. Finally, the blocks were attached at their reinforced surface to CFRP sheets at different bond widths and lengths with CFRP wrap anchorages applied over portions where high shearing stresses persist during pull-off testing. The results indicate that the physical status of concrete, the geometry of main CFRP sheets, and the extension of CFRP wrap anchorage are major factors that shape the benefit from the proposed anchorage technique. Empirical models, developed to predict bond strength and slippage at ultimate stress, show very good predictability of literature data. [ABSTRACT FROM AUTHOR]

Rock bolts are often used to support reinforcements in transportation, water conservation, coal mining and other industries, to reinforce slopes, tunnels and mines. They also play a key role in ensuring soil stability of foundation pits and slopes. Thus, it is very important to identify the defects of rock bolts. In order to address the issue that it is difficult to obtain the fault information of rock bolts, this paper proposes a method based on a grey cloud model to identify anchor defects. First, the coefficients of wavelet packet energy decomposition of the stress wave signal collected by a hammering anchorage system are selected as eigenvalues. Then, the eigenvalues are expanded into feature intervals, which are characterised by the grey cloud model with the peak value, left and right end-point boundary values, entropy and hyper entropy. Finally, the feature intervals are used for cluster and discriminant analysis of the anchorage quality. Optimisation of the model is achieved and the accuracy of the model in solving the problem of anchor rod defect identification is improved. The results show that the proposed method is feasible and effective in the identification of anchor defects. Additionally, this new method is more convenient and faster than the traditional method. [ABSTRACT FROM AUTHOR]

In posttensioned concrete members, the high local stress under the anchorage causes transverse tensile stress. Therefore, it is very important to predict the bursting force to determine appropriate reinforcement details. In the present work, the existing equations of the bursting force for the anchorage zone were evaluated and an equation for the bursting force based on finite element analysis was proposed to improve the model's accuracy. Parametric analysis was performed considering the anchorage shape, tendon angle, and eccentric distance. The analytical results indicate that the existing equations underestimate or overestimate the bursting force. The proposed equation is able to predict the bursting force reasonably well for an anchorage zone with rectangular bearing plate, cavity, and eccentric distance. [ABSTRACT FROM AUTHOR]

Experiments were performed to investigate the behavior of prismatic blocks with steel-fiber-reinforced reactive powder concrete subjected to centrally applied pressure in a limited area. The objective was to understand the reinforcement effect of orthogonal ties in reactive powder concrete anchorage zone. The three experimental variables were the volumetric ratio of the orthogonal ties, ranging from 4.63% to 5.83%; the ratio of the gross supporting area A b to the bearing plate area A l (local area aspect ratio); and the ratio of core area A cor to the bearing plate area A l (core area aspect ratio). The steel-fiber ratio by volume was 2%. Block behavior in terms of cracking and crack width is related to the bridging effect of the steel fibers and the confining influence of the orthogonal ties. No visible crack and constant stiffness of the specimen prior to cracking were observed. Possible brittle failure was improved to ductile failure, as measured by appearance of major cracks on the sides and ends of the blocks. The orthogonal ties have distinct effect of confining the core of the reactive powder concrete when the ratio of the area of the bearing plate to the area of the reactive powder concrete core surrounded by the orthogonal ties exceeds 1.0. [ABSTRACT FROM AUTHOR]

Ventilated facades systems have become a widely used solution for elevations of commercial buildings. Yet, those systems use metal frames and brackets that interrupt continuity of thermal insulation by creating point thermal bridges. The influence of anchorage systems on the total performance of walls is either neglected or simplified upon assumption that their influence is not important because the thermal insulation is thick enough. This article, based on three-dimensional analyses, demonstrates a significant impact of point bridges created by the anchorage systems of ventilated building facades on the heat loss. The results emphasize the need for individual calculations. [ABSTRACT FROM AUTHOR]

In order to study the efficiency of the confinement reinforcement in anchorage zones of posttensioning tendons, using both ordinary reinforced concrete (ORC) and high‐performance fiber reinforced concrete (HPFRC), an experimental research has been performed on the bearing strength of concrete prismatic specimens. This research also intended to assess both ultimate capacity and adequate serviceability of the local anchorage zone when reducing the concrete cross section and the confining reinforcement, both specified by the anchorage device supplier, by using an HPFRC. The experimental program included ORC prismatic specimens with 305 mm × 305 mm × 650 mm reinforced with spirals and a combination of spirals and stirrups, and HPFRC specimens with 210 mm × 210 mm × 420 mm reinforced with stirrups. The reinforcement steel strains were measured to monitor the steel yielding, to assess the relation between the strains of the inner (spiral) and outer (stirrups) levels of reinforcement and the uniformity of the confinement forces along the confined length. A comparison between the bearing strength obtained by experimental tests and by models found in the literature is also presented. From the strain measurements, it can be concluded that in the case where there are, simultaneously, two types of confinement reinforcement, the outer reinforcement is not as effective as the inner one. Therefore, when computing the bearing strength, the linear superposition of contributions of both spiral and stirrups for confinement can be nonconservative, leading to too high estimated load capacity. [ABSTRACT FROM AUTHOR]

Shear failure is the main failure mode of anchorage bolts in coal mines. To improve ground control, it is crucial to improve the shear strength of roadway anchorage systems. In this study, theoretical analysis, numerical simulation and laboratory experiments were carried out to study the shear characteristics of the cuneiform reaming anchorage. The results show that the cuneiform reaming anchorage can reduce the maximum shear stress on the cross section of the anchorage to improve the shear strength. The stress concentration near the joint planes can be transferred to middle parts of the bolts. Moreover, the cuneiform structure can also prolong the period in which the shear load of the anchorage decreases and shorten the period in which the shear load increases, thus reducing the shear load of the anchorage. This paper provides a new economical and practical method for raising the shear strength of an anchorage system and enhancing roadway stability. [ABSTRACT FROM AUTHOR]

Aiming to address the problems of stress concentration on conical wedge anchorage, a fiber-reinforced polymer cable anchorage with segmental variable stiffness of the load transfer medium was proposed. The key parameters that affect the anchorage behavior were investigated. The mechanical properties of the carbon fiber–reinforced polymer tendon and load transfer medium were tested. The failure mode, anchoring efficiency, stress, and displacement in the anchor zone were studied. The parameter optimization was performed using an experimentally verified finite element simulation. The parameters of the anchorage system with large capacity were evaluated. The results demonstrate that the compressive strength of the load transfer medium is the designed stress limit for the anchorage system. The cable does not slip or become damaged in the anchor zone, and the anchoring efficiency reaches 91%. The distribution of the shear and radial stress on the cable surface is smooth, and the stress concentration is greatly relieved. The result of the finite element simulation is consistent with the experimental values when the friction coefficient is 0.15, and the material and geometric parameters of the anchorage system with cable forces of 5000, 10,000, 15,000, and 20,000 kN are suggested. The geometric parameters of the anchor system with diverse cable capacity can be preliminarily designed based on the fitting equations. [ABSTRACT FROM AUTHOR]

Aimed at the needs for anchoring engineering in rammed earth sites, a composite optimization method for anchorage parameters based on desirability functions was proposed. The main purpose of the method is to obtain a good balance between the maximum anchoring force and the minimum site damage through optimization of the combination of anchor lengths and anchor hole diameters. The full factorial design was used in the experiment, and the response surface method was applied to build the analysis model. Then the desirability function in statistics was introduced into the optimization of anchor parameters, and the relationship between the multi-objective response and the anchoring parameter level was established. The results show that, when the anchoring force maximization and the site damage minimization goals are respectively satisfied, there will be a conflict between the corresponding anchoring parameters. The multi-objective response optimization can determine the feasible ranges of the anchoring parameters under the goal of response demand, which is convenient for engineering designers to visualize the anchoring parameters according to the actual engineering conditions. [ABSTRACT FROM AUTHOR]

In order to study the influence of yield supporting on the zonal disintegration of tunnel surrounding rock under layered lithology in deep tunnel and its anchoring mechanism. Through the analysis of the rock strain/displacement around the tunnel, it's clear that the combined support form of the rigid lining and the yielding anchor bolt has the best supporting affection in the four supporting forms, which can effectively suppress the zonal disintegration of the deep surrounding rock. At the same time, stress transfer is realized and the zonal disintegration trend of surrounding rock is weakened. Through the analysis of the internal force calculation results of the support structure, it shows that the combined yield supporting structure plays a supporting and anchoring role to the surrounding rock, and realizes the stress distribution, so that the stress field around the tunnel is more uniform. At the same time, the yielding anchor bolt can prevent the failure of the bolt in the deformation because of premature yielding, thus improving the supporting strength of the supporting structure. The research shows that the new combined support structure with rigid lining and pressure/yielding anchor is of great significance for inhibiting/suppressing zonal disintegration of deep rock tunnel. [ABSTRACT FROM AUTHOR]

• A novel anchorage system called additional ribs was proposed for FRP bars in NSM strengthening system. • Pull-out tests were conducted to evaluate the effect of different parameter, especially the additional ribs on the bond performance NSM FRP bars in concrete. • The local bond stress distribution and the transfer mechanism of specimens using additional ribs was analysed and expounded. Bond failure due to a lack of anchorage capacity is often observed when using FRP reinforcement as a strengthening method in RC structures, thus restricting the efficiency in upgrading their structural performance. To address this issue, our research group has recently developed a simple and innovative additional ribs anchorage system for FRP bars, which has been verified to have the high efficiency of improving the anchorage performance of FRP bars reinforced in concrete. As a promising strengthening method in RC structures, the near-surface mounted (NSM) fiber-reinforced polymer (FRP) technique has become popular. However, bond failure also exists in the NSM FRP strengthening system. It is also important to initiate a study on the bond performance of NSM FRP bars which are mounted in concrete using the proposed additional ribs. In this study, a total of 36 direct pull-out specimens and 12 beam pull-out specimens were employed. In particular, the influences of additional ribs on the bond behavior of FRP bars mounted in concrete in terms of the failure modes, local bond stress distribution, and load-slip curves were discussed. Several important parameters expected to affect the bond performance were investigated, namely, the type and the bonded length of the FRP bars, groove size and section configuration, and adhesive species. The test results and corresponding analysis in this paper demonstrated the feasibility and significant efficiency of using the proposed additional ribs anchorage system to enhance the bond performance of NSM FRP bars in concrete. [ABSTRACT FROM AUTHOR]

The debonding of carbon fibre-reinforced polymer (CFRP) strips from the surface of concrete is one of the main premature failure modes for concrete beams that are externally strengthened with CFRP strips. Many anchorage systems are developed to prevent or delay the debonding process in these beams in order to improve the ultimate load capacities. In this study, nonlinear finite-element analyses (FEAs) are performed by employing ABAQUS software to describe the load-deflection behaviour and ultimate loading capacities of concrete beams whose flexure has been strengthened using externally bonded CFRP strips with mechanical anchorages. First, the nonlinear finite-element model results are validated using the results of an experimental study previously carried out by the authors. In the experimental study, the variables investigated are the CFRP strip width and the number and the arrangement of the mechanical anchorages. A good agreement is demonstrated between the numerical and the experimental results. Then, a parametric study is conducted to investigate the effects of the mechanical anchorages on the ultimate load capacities of concrete beams. Consequently, the variable, the CFRP bonding length, is included into the finite-element models that are corrected with the experimental results, and equations involving many variables concerned with the ultimate loading capacities are suggested. Finally, an ultimate load capacity multiplier is proposed enabling the calculation of the ultimate load capacities of beams mechanically anchored with CFRP strips, with regard to the CFRP strip width, the bonding length, the number of mechanical anchorages and the arrangement of the variables. [ABSTRACT FROM AUTHOR]

Abstract An efficient anchorage system plays a significant role in the strengthening and repair of existing structures in prestressed carbon fiber reinforced polymer (CFRP) plates. In the present study, a novel wedge-bond anchor was proposed to provide a reliable anchorage load-bearing capacity for the prestressed CFRP plate. Accordingly, interface bond tests were conducted to optimize the anchor parameters. The results revealed that the minimum bond length of the wedge-bond anchor was 100 mm and 120 mm for the adhesives Tc and T1, respectively. After optimization, the weight of the anchor was reduced by 58.3%. A mechanical model was built to analyze the load transfer path and evaluate the anchorage bearing capacity. Based on these, the ultimate anchorage bearing capacity was predicted to be higher than 4.70 GPa and 4.10 GPa for the adhesives Tc and T1, respectively. Tensile tests of the optimized anchor showed that a) the stress in the anchorage zone of the CFRP plate was distributed uniformly, and b) the stress concentration of CFRP in the anchor was avoided, which provided a higher anchorage bearing capacity. The extension applications of wedge-bond anchor were carried out for a larger size of CFRP plates (100 mm × 1.4 mm). Accordingly, it successfully led to CFRP bursting, yet no debonding occurred in the anchor. Highlights • A novel wedge-bond anchor was designed and optimized to provide a reliable anchorage capacity for the prestressed CFRP plate. • Mechanical analysis revealed the anchorage capacity of the anchor satisfied the rehabilitation requirements of CFRP plates. • Tensile validation tests showed the rational load transfer and the decreased stress concentration of anchoring system. • The wedge-bond anchor was successfully extended the application of the CFRP plate to larger sizes. [ABSTRACT FROM AUTHOR]