Anchor Design Research Articles

Finite Element Combined Design and Material Optimization Addressing the Wear in Removable Implant Prosthodontics.

Wear at the male-female interface of retentive elements in implant-supported removable prostheses is the most frequent complication in such applications. The lack of an ideal/optimal insertion path, as well as the fabrication inaccuracies, are the primary contributors to this issue. A male attachment with a common ball anchor enhanced by lateral flexibility was investigated as a solution, compared to the widely used rigid ball anchor design. A parametric finite element analysis was performed to compare the wear-inducing maximum strain at the female polymer counterpart by various attachment designs made from titanium and Nitinol. The evolution of mechanical strains causing wear in the female part, as well as the contribution of stresses and martensitic transformation in the implant's flexible shaft, were evaluated under several insertion misfit scenarios. Results indicate that introducing a long flexible shaft in the titanium implant reduced maximum strains in the female attachment part by up to 61% as compared to the solid ball anchor. Further improvement was observed by using the shape memory alloy Nitinol as shaft material, leading to a minor reduction in stress and strain at the contact surface but allowing for a shorter abutment. Finally, the optimized Nitinol implant design with a short, necked flexible shaft promoting martensitic transformation at low plateau stress resulted in an approximate 90% reduction in maximum strains at the inner surface of the female part during manual insertion, which indicates a significantly reduced wear phenomenon at the contact.

Component‐section transverse‐pressure effect on internal damage and failure mode of post‐installed rebar

AbstractA post‐installed rebar (PIR) is commonly used to establish structural connections between new components and existing structures, such as structural member extensions or concrete layer overlays in the construction/strengthening/retrofitting of buildings or bridges. In joint connections, the anchored PIR system always bears a non‐negligible compression in the component section, which is derived from the loads and self‐weight and has a confinement effect on the anchorage zone. However, excessive pressure can result in the fracture of the adhesive component, thereby leading to brittle failure in the PIR system. Owing to the important role of the adhesive component in the PIR system, this study is focused on the internal damage to the PIR system, and the effect of transverse pressure on the failure modes is investigated. This study comprises an experimental investigation of the failures of a PIR system under transverse pressure and a description of the internal damages based on the test results. Finally, an elastic analysis was established to explain the internal cracking and investigate the stress distribution in the PIR system. The tests on 34 pull‐out specimens showed two typical failures for the PIR system under transverse pressure (adhesive–rebar [A–R] interface failure and adhesive fracture failure). The A–R interface failure resulted from the shearing failure in the adhesive component, while the adhesive fracture failure resulted from the propagation of longitudinal and transverse cracks. The elastic analysis indicated that cracking in the concrete and adhesive component was dominated by circumferential stress, and the rebar rib direction and adhesive component thickness had a significant influence on the stress distribution. Based on this, some suggestions for anchorage design were made.

Calibration and implementation of a design tool for drag anchors in clay

Abstract Drag anchors are considered as one of the most applicable anchor solutions for floating offshore wind as they can be used for a wide range of soil conditions. For feasibility studies of floating offshore wind farms different anchor concepts needs to be compared in order to select the most proper anchor solution. To do so, the level of details in the analysis for the various anchor types must be similar. Currently design charts are adopted as a simple design method for drag anchors. However, design charts are developed for specific soil conditions, and do not account for site specific soil conditions. To have similar precision, as analytical solutions for suction anchors, a simple design methodology that can account for site specific soil conditions for drag anchors must be adopted. This paper presents an example for how a simple analytical solution can be calibrated against design charts, which makes it possible to account for site specific soil conditions, resulting in a better basis for comparing early stage drag anchor design to other anchor solutions.

Mechanical Properties of Fully-Grouted Bolts Support Based on Compression Tests of Anchored Rock Mass

The mechanical properties of fully-grouted bolt support are critical for the safety of support engineering works. To study the influences of factors including the bolt length and diameter, strength of the rock, and fracture angle on the mechanical properties of fully-grouted bolt support, compression tests were conducted on an anchored rock mass, considering the shortcomings of pullout tests on bolts. The discrete element software PFC2D (4.0) was adopted for numerical simulation and analysis from two aspects, namely, the stress distribution and anchorage force supplied by such bolts. The research found that by increasing the bolt diameter and length as well as the strength of the rock, the maximum anchorage force of bolts increases. Whereas the stress distribution of all bolts increases at first and then decreases along the bolts, and there is only one peak on the stress distribution curves, which also gradually shifts to a greater depth. In a fractured rock mass, the maximum anchorage force of bolts decreases, then increases (and is minimized at a fracture angle of 45°) with the decrease in fracture angle. The influence of fractures with different angles on the stress distribution of bolts is mainly reflected in the fracture zone. The bolt stress decreases abruptly in the zone with a fracture angle of 90°, forming a valley. The bolt stress increases suddenly in the zones with fracture angles of 60° and 45°, thus forming peaks. The bolt stress does not increase or decrease suddenly in the zone with a fracture angle of 30°. Therefore, it necessitates consideration of the influences of fractures on the anchorage force and the selection of bolts of appropriate size during anchorage design. After installation, the bolt stress should be monitored for stability and early warning of anchored rock mass according to changes in the stress provided.

Development of Double Frame Method to improve the seismic performance of low-rise reinforced concrete buildings

ABSTRACT The current paper proposes a seismic reinforcement method that uses a double frame and is called the Double Frame Method (DFM). Performance tests are conducted to assess the material suitability of a post-installed anchor that directly connects the existing frame to the double frame, while a shear performance test is conducted to examine the vertical connector. The performance of column members with and without DFM reinforcement was compared and evaluated. Ultimately, we have fabricated a two-story, one-span reinforced concrete existing frame test specimen and a DFM reinforced frame test specimen that we can use to examine the effect of improving seismic performance through repeated loading tests. The result of the anchor’s pull-out test show that the average tensile strength is 27.9 kN, exceeding the average design strength of 21.7 kN suggested by the manufacturer. The shear strength test results of the anchor show an average value of 28.7 kN. Meanwhile, the vertical connector test show that the internal force per anchor is 46.83 kN, which is approximately 163% more than the single anchor design shear strength of 28.7 kN. As a result of the DFM-reinforced column test, in the actuator direction, the yield strength is improved by about 120%, while the maximum strength is improved by about 150–180%. As a result of the two-story frame experiment, the double frame reinforced specimen shows a maximum strength of about 4.0 to 4.5 times that of the non-seismic specimen.

Adaptive anchor learner for object detection

Abstract There is a growing interest in advancing object detection and its various applications. Promising performance is achieved by using anchor-based detectors while the difficulty is encountered. The performance is sensitive to the hyper-parameters related to anchor boxes, which are manually determined and are task-specific. To address the issue, an anchor learner is proposed in the paper, which automatically learns adaptive anchor from the data, and the difficulty of anchor design for a specific task is thus avoided. Specifically, the method we propose comprises a backbone network and two fully connected branches, and these two branches learn anchor scales and aspects ratios, respectively. We use RGB and ground-truth mask image data as the network input. Importantly, the anchor learner can be embedded into any anchor-based object detector. Experiments are performed on the datasets Visdrone 2019, UAVDT, and DOTA, respectively. Experimental results demonstrate that our proposed method markedly enhances object detection performance.

Mechanism of Rock Mass Detachment Using Undercutting Anchors: A Numerical Finite Element Method (FEM) Analysis.

Undercutting anchors are structural elements used in construction and geotechnics to stabilize both structures and soils. Their main applications include stabilizing slopes and embankments, reinforcing foundations, and providing support during tunnel construction and other underground works. The authors propose the use of these anchors in rock mass detachment technology. This article presents a comprehensive analysis of the mechanism behind rock mass detachment using an undercutting anchor. Particular attention is given to the influence of parameters such as the fracture energy of the medium and the coefficient of friction between the medium and the anchor head on the detachment process of rock elements during anchor expansion in the drilled hole. Numerical FEM analysis was employed to model the effect of changes in the shape and size of failure cones under varying simulation conditions. The discussed problem is crucial for evaluating the effectiveness of this anchor design under non-standard conditions, particularly in the unconventional destruction of rock media.

Metoda za postizanje značajnih sila sidrenja unutar ograničenih dubina ugradnje u tanke betonske ploče i ljuske ojačane vlaknima

Contemporary fibre-reinforced concrete provides new opportunities for the design of thin concrete elements with substantial bending strength. To realise the full benefits of reduced weights owing to the reduced structural thickness, new anchorage elements must be developed that can sustain high anchorage forces within limited embedment depths in thin plates. This paper introduces a new anchorage design for concrete plates or shells that provides high tensile forces between 4 and 6 kN within a small embedment depth of 5 mm. The proposed design concept includes a two-stage anchorage mechanism that provides the required tensile strength and ductility for the anchorage. Achieving such anchorage capabilities within the limited embedment depth of thin concrete elements enables the production of lightweight concrete plates and shells.

Load transfer model and failure prevention measures of a mechanical-type anchorage for anchor cable in deep roadway

In this paper, the load transfer mechanism of a mechanical-type anchorage is analyzed and studied. The stress distribution on the surface of the anchor cable is clarified, and the means of mechanical analysis and Abaqus finite element method are used. Results indicated there is no stress concentration, and the peak value indicated by the anchor cable appears near the loading end, and the peak value is about 60 MPa larger than the tensile strength. The results of the tensile test show that the failure mode of the anchor cable is the necking fracture of the steel wires, which indicates that the steel reaches the yield limit stress. The anchor efficiency of mechanical-type anchorage is high, which can effectively exert the tensile strength of anchor cable. In deep mine roadway, two failure modes of anchor cable are summarized when mechanical-type anchorage is used. Including shear failure and slippage failure under dynamic action. Aiming at the shear failure behavior, a new type of anchorage was invented, including the self-aligning and shear resistance functions of the anchor cable, and an experiment was carried out. Results indicated anti-shear anchorage can effectively solve the problem of anchor cable failure caused by shear. For the problem of anchor cable slippage failure under dynamic action. The parameters affecting the stability of mechanical-type anchorage are analyzed by means of theoretical analysis and numerical simulation. Results indicated reducing the bevel angle of wedge and barrel, the difference angle between them, and increasing the friction coefficient μ between wedge and barrel can increase the stability of mechanical-type anchorage. The research content of this paper can provide reference for the design of mechanical-type anchorage in similar underground engineering.

3D-printed porous titanium suture anchor: a rabbit lateral femoral condyle model

BackgroundThe inclusion of a connecting path in a porous implant can promote nutrient diffusion to cells and enhance bone ingrowth. Consequently, this study aimed to evaluate the biomechanical, radiographic, and histopathological performance of a novel 3D-printed porous suture anchor in a rabbit femur model.MethodsThree test groups were formed based on the type of suture anchor (SA): Commercial SA (CSA, Group A, n = 20), custom solid SA (CSSA, Group B, n = 20), and custom porous SA (CPSA, Group C, n = 20). The SAs were implanted in the lateral femoral condyle of the right leg in each rabbit. The rabbits (New Zealand white rabbits, male, mean body weight of 2.8 ± 0.5 kg, age 8 months) underwent identical treatment and were randomized into experimental and control groups via computer-generated randomization. Five rabbits (10 femoral condyles) were euthanized at 0, 4, 8, and 12 weeks post-implantation for micro-CT, histological analysis, and biomechanical testing.ResultsAt 12 weeks, the CPSA showed a higher BV/TV (median 0.7301, IQR 0.7276–0.7315) than the CSSA and CSA. The histological analysis showed mineralized osteocytes near the SA. At 4 weeks, new bone was observed around the CPSA and had penetrated its porous structure. By 12 weeks, there was no significant difference in ultimate failure load between the CSA and CPSA.ConclusionsWe demonstrated that the innovative 3D-printed porous suture anchor exhibited comparable pullout strength to conventional threaded suture anchors at the 12-week postoperative time-point period. Furthermore, our porous anchor design enhanced new bone formation and facilitated bone growth into the implant structure, resulting in improved biomechanical stability.

Use of an Osseointegrated Intraosseous Transcutaneous Amputation Prosthesis for Amputated Fingers Is Followed by Frequent Infection and Implant Removal

ABSTRACT Introduction We report on the outcomes of using a custom-built osseointegrated (OI) intraosseous transcutaneous amputation prosthesis (ITAP) as a bone anchor for prosthetic reconstruction of a series of amputated fingers. The aim of ITAP was to reduce the risk of failure due to infection by creating a biological seal at the skin-implant interface. Methods and Results A total of 14 patients who suffered from amputations of their digits at a variety of different levels were recruited. Eleven patients (20 implants) underwent treatment with an implant based on the ITAP principle. With the exception of one patient (1 implant), all implants were removed by 9 years after insertion. Patients requested removal because of recurrent infections, exposure of the flange structure (unique to ITAP), loosening of the implant, and inability to secure a prosthesis to the implant. Conclusions The ITAP principle does not work when used as part of the design of an OI bone anchor for prosthetic reconstruction after finger amputation. Clinical Relevance Statement This study suggests that there are major problems with the principles underlying the design of the ITAP implant when used in humans. Future studies of OI implants using the principles of ITAP may be at risk of similar problems.

Effect of cyclic loading on the ultimate tensile strength of small metallic suture anchors used for attaching artificial tendons in rabbits.

Suture anchor failures can lead to revision surgeries which are costly and burdensome for patients. The durability of musculoskeletal reconstructions is therefore partly affected by the design of the suture anchors. The purpose of the study was to quantify the strength of different suture anchors whose sizes are suitable for attaching artificial Achilles and tibialis cranialis tendons in a rabbit model, as well as determine the effect of cyclic loading on the anchoring strength. Four anchors (two with embedded eyelet and two with raised eyelet, n=5 per group) were tested with cyclical loading (1000 cycles and 4.5 mm/sec) and without cycling, to inform the failure loads and mode of failure of the suture anchors. An eyebolt screw with smooth eyelet was used as a control for the test groups. All samples in all groups completed 1000 cycles and failed via suture breakage in both test conditions. All anchors had failure loads exceeding the peak Achilles tendon force in rabbits during hopping gait. The data analysis showed an effect of anchor type on the maximum tensile force at failure (F max ) in all suture categories but not an effect of loading condition. Also, the Anika anchor had a significantly less adverse effect on suture strength compared to Arthrex anchor (p=0.015), IMEX anchor (p=0.004) and Jorvet anchor (p<0.001). We observed a greater percentage of failure at the mid-section for the anchors with the raised eyelets compared to the anchors with embedded eyelets, which all failed at the knot. Anchors with embedded eyelets had clinically preferred mode of failure with less adverse effects on suture and, may be more reliable than anchors with raised eyelets for attaching artificial Achilles and tibialis cranialis tendons in rabbits.

Laboratory Tests of Large-Scale Block Models on the Load Transfer and Failure Mechanisms of Rock Masses Subjected to Anchor Loading

This paper presents a laboratory testing rig designed to investigate the failure mechanisms and load transfer of rock masses under rock anchor loading. The study revealed that joint patterns significantly affect the strength and capacity of the rock mass, with existing design approaches based on apex angles of 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document} or 60∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document} found to be potentially overly conservative. Joint orientation and spacing should be included in the anchor design to obtain a more precise design criterion. In all the studied patterns, increasing the horizontal and vertical stress increased the block models’ capacity, and load arching did not occur in the model with an unfavourable joint orientation. This study also revealed that the failure surface followed the joints in all tests and that the block model capacity was significantly higher than estimated with the design principle based on the weight of the overlying rock. The findings of this work have important implications for designing rock anchoring systems in mining and civil engineering demonstrate that joint orientation and block size significantly affect the rock mass capacity. This study confirms the need to consider the influence of in situ stresses on rock mass capacity when designing of rock anchors. Overall, this work guides the development of more precise design criteria for rock anchors, contributing to more efficient and effective rock engineering practices.

Analytical Solution for Seismic Stability of 3D Rock Slope Reinforced with Prestressed Anchor Cables

Currently, the study of analytical solutions for the seismic stability of slopes under anchorage conditions is one of the hottest subjects in engineering. In this paper, an analytical solution for the seismic safety of the three-dimensional (3D) two-stage rock slope reinforced with prestressed anchor cables governed by the nonlinear Hoek–Brown criterion was deduced, in which the analyses of seismicity were performed by the latest modified pseudo-dynamic method. This method supplements the consideration of the damping effect of the rock medium on seismic waves, which is more in line with the real seismic situation. A mathematical geometric model was developed for calculating the external forces work and internal energy dissipation acting on 3D rotating rock masses reinforced with prestressed anchor cables, in which the seismic work rate was calculated using a new layer-by-layer superposition summation method. The analytical solution of the safety factor could be collated as an explicit function of several variables, and then, the optimal value was obtained by the Particle Swarm Optimization (PSO) algorithm. To corroborate the accuracy of new analytical solutions, the results were contrasted with those of the pertinent literature. The results of the two comparisons were very close. Ultimately, the sensitivity analyses and coupling effects of seismic pseudo-dynamic factors and prestressing anchorage factors were carried out. It was found that even small seismic intensities had a large effect on the stability of rock slopes with developed joints. Increasing the number of steps and prestressing anchors can effectively improve the stability of rock slopes under seismic effects. The conclusions have significant implications for the anchorage design of the 3D two-stage rock slope as seismic events occur.

Anchor chain profiles in sand based on centrifuge model tests

The rapid development of floating wind turbines (FWTs) has brought new challenges to their mooring systems in shallow water of 50-200 m. The sand seabed, which is widely distributed in offshore regions, is often encountered in the service of FWTs and influences the anchor and mooring line design. The anchor chain is primarily adopted as the part interacting with the seabed, and its configuration in the seabed is vital for anchor design. However, a complete understanding of the chain configuration in sand is yet to be achieved. To address this, a group of centrifuge model tests using a model chain were conducted to simulate the chain embedment behavior in carbonate sand. During the tests, the chain position and soil deformation were captured using the Particle Image Velocimetry (PIV) method. A calculation model was adopted to predict the chain configuration in the sand, compare it with the centrifuge test results, and then analyze the differences between them. Finally, suggestions for model improvement were discussed.

Geometrically engineered mass sensing CMOS-MEMS resonators for temperature compensation via folded anchors

We present, for the first time, a single-layer plate resonator with specific folded anchors capable of reducing the temperature coefficient of frequency (TCF) by two orders of magnitude compared to straight beams. Folded anchors provide differential strain through either compressive or tensile thermal stress depending on the anchor design and, in turn, allow for positive and negative temperature-induced frequency change components. With a nominal 2 MHz frequency, we experimentally report a frequency shift of 2500 ppm over a temperature span from 0ºC to 90ºC using an optimal anchor folding aspect ratio. The frequency-temperature curve exhibits a turnover point at 27ºC granting a unique opportunity to, in a future application, complement this passive strategy with an active micro-oven for negligible TCF. The proposed approach main advantage relies on its mechanical design-level implementation exploiting a geometrical engineering strategy than can be directly extended to other topologies. This technique reveals as particularly suited for ultra-sensitive mass sensing applications based on microelectromechanical systems (MEMS) resonators where single-layer resonators are optimal thanks to their minimum footprint, attaining minimum mass structures. Results demonstrate that adoption of the proposed folded anchors strategy decreases effectively the thermally induced frequency fluctuations within the system intrinsic noise level.

A novel anchor method for large tonnage CFRP cable: Anchorage design and full-scale experiment

This study introduces a novel three-segment CFRP cable anchorage to address stress concentration challenges in CFRP cable anchors. The anchorage features a continuously varying inner cone angle along the anchor length to prevent excessive radial stress on the CFRP cable. The radial stress distribution is theoretically analyzed, followed by a numerical simulation design using the Tsai-Wu failure criterion and the anchor system's equivalent stiffness as evaluation indices. The results demonstrate a 47.06 % and 45.73 % reduction in the radial stress peak of the novel anchorage compared to the inner cone and inner cone + straight cylinder anchorage, respectively. Importantly, beyond an anchor length 23 times the equivalent diameter of the CFRP tendon, increasing length has a marginal impact on anchor efficiency but diminishes equivalent stiffness. Positive effects are observed by increasing the inner cone segment proportion and adjusting the inner cone angle within the 2° to 4° range. Conversely, increasing the bonding medium thickness reduces anchor efficiency and equivalent stiffness. Experimental verification indicates the anchor system achieving 99.83 % anchor efficiency. Moreover, the axial strain of CFRP tendons in the anchor zone exhibits a linear trend along the anchor length, with test stresses at corresponding positions consistent with FE calculation results.

Calculation and Analysis of Load Transfer Characteristics of Tensile Anchors for Geotechnical Anchoring Systems

In order to explore the problems of load transfer and anchorage mechanisms of tensile anchors under pull-out load for geotechnical anchoring systems, a step-wise mathematical model is established which considers the linear–nonlinear shear stress and shear displacement of the anchorage segment, using an elasto-plastic constitutive model. The displacement, axial force, and shear stress of the anchorage interface in different stages (elastic, plastic, and debonding) are analyzed and solutions are derived. And the theoretical solutions for the ultimate pull-out load of the anchor at each stage are also presented. Two in situ pull-out tests are used to verify and apply these findings in engineering. The results show that the stepwise composite model could reflect the bonding, softening and residual characteristics of the anchoring interface. In the process of the pull-out load increasing, the pulling end of the anchor initially enters the plastic stage and the debonding stage, respectively, and the failure of the anchor occurs at the pulling end, and as the axial force transfers down deeper, the damage gradually spreads deeper. The axial force distribution of the anchorage section is a monotonically decreasing curve, and the peak point of the shear stress gradually moves deeper. The calculation results of the axial force distribution curve and load–displacement curve of the anchor are in good agreement with the measured values, which verifies the rationality and reliability of the theoretical prediction method. This method can provide a theoretical reference for the load transfer analysis and design of tension anchors for geotechnical anchoring systems.

Stability Analysis of HSD Tank Against Dynamic Response

The existing HSD tank F-6302 has suffered damage in the form of corrosion which has caused the plate thickness to decrease. Developments in analysis methods and tank design standards have an effect on determining the stable capacity of the tank, so it is suspected that this tank is unstable. This study aims to analyze the stability of the existing HSD tank F-6302 to seismic response. The analysis was carried out by collecting structural property data of the tank, modelling the tank in FEM with a combination approach of finite element model and auxiliary mass, and evaluating the stability value of the tank using the equation issued by API 650:2020 to assess whether the tank is stable or not. The analysis results confirmed that the tank was unstable to earthquake loading. This is shown by the tank anchorage ratio values of 2.59 for the empty condition and 3.21 for the full condition. Both are greater than the stable limit value of 1.54. In the future, it is recommended to perform tank shell design and anchorage design on the tank.

Novel 3D Printing Designs of Drywall Anchor

In this research project, the unique designs for 3D printed drywall anchors in this study were inspired by the skin of animals seen in nature, including reptiles, fish, and butterflies. The tough skin of these animals inspired our drywall anchor design. Engineered nylon produces drywall Anchors, one-piece, self-drilling drywall, and hollow cavity anchors. It may be installed in walls as thin as 12mm and optimized for drywall usage. You can screw with the nylon piece. A drywall sleeve anchor is an insert or sleeve made of plastic inserted into a tiny pilot hole. The sleeve enlarges as the drywall metal screw provided is threaded into it. This increases the shear strength, which helps the metal screw remain in the wall. Drywall sleeve anchors are often the sort of drywall anchor that has the lowest price point. They work well for lightweight products. The purpose of a drywall anchor is to firmly mount framed artwork, mirrors, clocks, and shelving to walls.