Anchorage System Research Articles

Acute Effects of a Haptic Anchor System on Postural Sway of Individuals with Parkinson's Disease: A Preliminary Study.

Some investigators have demonstrated that an anchor system can improve postural control in elderly persons during balance tasks, but none have reported on the use of this approach in individuals with Parkinson's disease (PD). Therefore, we aimed to evaluate the effect of an anchor system on postural sway in elderly individuals with (n = 13) and without (n = 14) PD. In this cross-sectional study, we measured postural sway with a force platform based on the Clinical Test of Sensory Interaction of Balance (CTSIB). We calculated center of pressure (COP) parameters, as a function of time, based on the ellipse sway area (cm2) and evaluated self-efficacy for postural control based on the degree of difficulty in each task. With the anchor system (i.e., handheld ropes attached to weights on the floor), we observed a significant reduction in the ellipse sway area in the semi-tandem position among individuals with PD (p = .04). For participants without PD, there was no significant difference in sway with or without the anchor system in all positions. Also, for participants with PD, there was an improvement in self-efficacy for postural control associated with the anchor system in several positions while there was only a self-efficacy improvement with the anchor system in the semi-tandem position for those without PD. Acute use of a haptic anchor system reduced postural sway in the semi-tandem position in individuals with PD, and the anchor system generally improved postural control self-efficacy for body sway in individuals with PD.

Cover Picture: Geomechanics and Tunnelling 4/2022

AbstractTo increase overall safety, standardize Croatia's highway network, and adapt to the increased traffic to and from European countries, the Croatian Government decided to build a second tube for the Učka Tunnel – the third‐longest tunnel in Croatia. DSI Underground produced and supplied anchor systems and equipment to support excavation. (photo: DSI underground)

Hybrid and patch anchors for prevention of IC debonding in RC planks flexurally strengthened using FRP

One of the predominant failure modes of reinforced concrete (RC) members strengthened in flexure using fiber reinforced polymers (FRP) is intermediate crack induced (IC) debonding.This failure mode is usually brittle, premature and constitutes a significant underutilisation of the FRP material. To address this type of failure, design guidelines enforce strict limitations on the allowable FRP strain level which can be used in design. In order to suppress IC debonding failure modes, researchers have explored various anchorage systems with varying degrees of success. This paper investigates the use of patch anchors and hybrid anchors to suppress IC debonding failure. An experimental program is presented where RC planks are strengthened with FRP laminates and sheets and anchored using different arrangements. The results show that the addition of two hybrid anchors to the ends of the FRP plate results in significant load and deformation increases compared with unanchored planks.

Pull-out Strength of Suture Anchor and Torque of Buddy Anchor for an Osteoporotic Humeral Head in Rotator Cuff Repair: Parallel Versus Divergent Insertion

Background: The buddy anchor technique is useful to reinforce loose anchors in the osteoporotic humeral head during arthroscopic rotator cuff repair. However, theoretical parallel insertion of the buddy anchor to index a loose anchor is challenging in arthroscopy and can widen the entry site and decrease structural integrity. Purpose: To investigate and compare the biomechanical stability between 2 buddy anchor insertion techniques (parallel insertion vs divergent insertion) in the osteoporotic humeral head. Study Design: Controlled laboratory study. Methods: A total of 24 paired fresh-frozen cadaveric shoulders were used, and each pair was randomly assigned to either the parallel insertion group or the divergent insertion group. In the parallel insertion group, the buddy anchor was inserted parallel to the index loose anchor. In the divergent insertion group, the buddy anchor was inserted at a 20° angle in the medial direction to the index loose anchor. The insertion torque of the buddy anchor and ultimate pull-out strength of the index anchor were measured and compared between the 2 groups. Results: The mean maximum insertion torque was significantly higher in the parallel insertion group (16.1 ± 1.8 cN·m) compared with the divergent insertion group (12.0 ± 1.5 cN·m) (P < .001). The mean ultimate pull-out strength was significantly higher with divergent insertion (192.2 ± 28.6 N) than with parallel insertion (147.7 ± 23.6 N) (P < .001). Conclusion: For application of the buddy anchor system in the cadaveric osteoporotic humeral bone model, divergent insertion showed better ultimate pull-out strength than conventional parallel insertion, despite inferior maximum insertion torque. Clinical Relevance: The results of this study widen the applicability and accessibility for the buddy anchor system.

Numerical Simulation of Ground Anchor-Soil Nail Retaining Systems for Academic-Learning Purposes

The ever-expanding urban architecture in developing areas requires more land space for construction purposes to be available. For this, utilizing the sub-surface areas through excavations in populous cities is now on the increasing trend. Two major concerns in such excavation projects are excavation-wall stability and the induced ground settlements which can be countered by a soil nailing-ground anchor system. In this regard, influential factors such as nail length and nail inclination angles can affect the overall performance of stabilized ground. Therefore, the focus of the present study is on how the aforementioned influence excavation-induced ground deformations. The numerical simulation is conducted using the software Plaxis 2D. The established numerical models help to explain how changes in the nails’ inclination angles and anchor lengths can change the observed behavior of the walls; from which helpful tips for practicing engineers are drawn accordingly. Such results could also be utilized for classroom presentations to aid students’ understanding of geotechnical engineering concepts.

Influence of Cross-Section Shape and FRP Reinforcement Layout on Shear Capacity of Strengthened RC Beams.

The evaluation of the shear capacity of an FRP-strengthened reinforced-concrete beam is challenging due to the complex interaction between different contributions provided by the concrete, steel stirrup and FRP reinforcement. The shape of the beam and the FRP inclination can have paramount importance that is not often recognized by the models that are suggested by codes. The interaction among different resisting mechanisms has a significant effect on the shear capacity of beams, since it can cause a reduction in the efficiency of some resisting mechanisms. A comparative study of the performance in the shear resistance assessment provided by three models with six different effectiveness factors (R) is performed, considering different cross-section shapes, FRP wrapping schemes, inclination and anchorage systems. The results revealed that the cross-section shape, the FRP inclination and the efficiency of the FRP anchorages have a significant effect on the shear strength of beams. The analysis results show that the three models are able to provide an accurate average estimation of shear strength (but with a coefficient of variation up to 0.35) when FRP reinforcement orthogonal to the beam axis is considered, while a significant underestimation (up to 19%) affected the results for inclined FRP reinforcement. Moreover, all the models underestimated the resistance of beams with a T section.

Seismic response distribution expressions for rocking building contents under ordinary ground motions

Analytical expressions are proposed for predicting the rocking response of rigid free-standing building contents subjected to seismic-induced floor excitations. The study considers a wide range of rigid block geometries and seismic floor acceleration histories that were recorded during actual earthquakes in instrumented Californian buildings, so as to cover, in a fully probabilistic manner, the entire spectrum of potential pure rocking responses, i.e. from the initiation of rocking up to the block overturning. Contrary to past observations on anchored building contents (prior to any failure in their anchorage system that could alter their response and mode of failure), it is shown that the response of free-standing blocks is not influenced by the predominant period of the supporting structure. The proposed set of equations can be utilised for estimating the response statistics and consequently for undertaking an analytical seismic fragility assessment on rocking building contents.

A novel variable curvature clamping anchor for the multilayer CFRP plate cable: Concept, numerical investigation, and design proposals

This paper proposed a novel variable curvature clamping anchor (VCCA) for the multilayer carbon fiber-reinforced polymer (CFRP) plate cable and systematically evaluated the anchor performance using the finite element (FE) method. The design concept of the anchor, function of variable curvature waveform, anchor configuration and components design were first presented, then the stress distribution of the CFRP plate with different layers and failure mode of the anchor system were investigated. The six parameters affecting the anchor performance were also studied, including the number of waveforms, bolt preload, anchor length, thickness of ear plate, thickness of clamping plate, and thickness of clip. Finally, the design proposals of the anchor were given. The results indicate that the peak compressive stress has been successfully transferred from the loading end to the back of the anchor, and the interfacial shear stress of the CFRP plate was small and less than one-sixth of the shear strength. In addition, the failure of the anchor system occurred in the cable body part and not inside the anchor. The number of waveforms and the thickness of the clip slightly affected the peak transverse compressive stress, whereas the bolt preload, anchor length, ear plate thickness, and clamping plate thickness had an important influence on the axial stress distribution and peak transverse compressive stress. The novel VCCA proposed in this paper has essential engineering value and significance, filling the gap of the anchor for the multilayer CFRP plate cable, contributing to promoting the application of large-tonnage CFRP plate cable in bridges and space structures, and landing a solid foundation for subsequent experiments.

Behavior of bond-slip relationship of lightweight and normal weight geopolymer with various FRP sheets using end-groove anchorage

In this study, the effect of using an end-groove anchorage system (EGA) on the bond-slip behavior between fiber-reinforced polymer (FRP) sheets and both normal weight geopolymer (NWG) and lightweight geopolymer (LWG) concrete was investigated by considering the effects of different types of FRP sheets (CFRP, BFRP, and GFRP), FRP bonding lengths of 50 and 100 mm, FRP bonding widths of 50 and 75 mm, and with and without an EGA system. A total of 96 specimens of NWG and LWG concrete were cast, bonded with FRP sheetsand tested under double-shear tension. The results of employing EGA revealed that the bond-slip behavior of NWG specimens differed from that of LWG specimens. Using the EGA system significantly enhanced the bond force by an average of 16 % and 18 % for NWG and LWG, respectively. However, the ultimate slippage of NWG specimens was reduced by as high as 60 % as a result of using the EGA system, but it contributed to increasing the ultimate slippage remarkably by as high as 73 % for LWG concrete specimens. It's worth noting that the bond-slip behavior of CFRP sheet outperformed all other types of FRP sheets for both NWG and LWG concrete. The type of geopolymer concrete, the kind of FRP sheets, and the EGA process all influence specimen failure modes. The EGA system was more favorable for the bond failure of CFRP sheet and NWG concrete specimens, resulting in the avoidance of sudden debonding of CFRP composite and block contacts. A bond-slip model was proposed in this study to predict specimen bond force and slippage. The model was well fitted to the experimental data and appeared to have potential as a practical application which is the first and only model in the literature in this field.

Performance of a U-shaped anchoring system for cable-stayed bridges

An innovative U-shaped anchoring system was previously proposed to prevent the cracking of cable-pylon anchorage zones of concrete pylons in long-span cable-stayed bridges. The anchoring system transfers the cable force to the concrete pylon in the form of radial pressure, which fundamentally prevents the tension cracking of the concrete pylon column. In this study, the mechanical performance of the U-shaped anchorage system was investigated using finite element analysis. Subsequently, the fatigue performance of the steel strand in the U-shaped saddle, the anti-sliding performance of the U-shaped saddle, and the corrosion resistance of the steel strand were experimentally studied. The results of finite element analyses indicate that the U-shaped anchorage system significantly avoids concrete cracking in the cable anchorage zones provided that the strength grade of concrete filler is no less than C30. The experimental results show that the steel strand with polyurea coating has sufficient fatigue resistance as well as adequate anti-corrosion performance, and the anti-sliding performance of the anchoring system is sufficiently good. These critical studies validate the superiority of the U-shaped anchoring system with polyurea-coated steel strands, which should observe wide engineering applications in long-span cable-stayed bridges.

Ultrasonic-based tensile force estimation for cylindrical rod at various temperature conditions

This study presents the development of a tensile force estimation technique based on the ultrasonic bulk wave for cylindrical rod in a suspension bridge anchor system. Three piezoelectric macro fiber composites (MFC) transducers are installed on the surface of a cylindrical rod specimen for the generation and sensing of ultrasonic bulk waves. Ultrasonic responses are obtained at various tensile force levels and temperature conditions, and the relationship between the time lag of the ultrasonic response and the tensile force is established. In particular, the temperature effect on the tensile force estimation is theoretically derived and compensated for field applications. The originality of this study includes (1) theoretical derivation and investigation of the relationship between an applied tensile force level and the time lag of an ultrasonic response considering the variations of temperature, density, and elastic modulus, (2) development of a tensile force estimation and temperature compensation technique without temperature measurement, and (3) application to the tensile force estimation of the rod structure commonly used in a suspension bridge anchor system. The performance of the developed tensile force estimation technique was examined based on mock-up experiments of the rod structure of a real suspension bridge anchor system.

Expanding the concept of orthodontic camouflage for a skeletal Class II camouflage case through the use of skeletal anchorage system

This study aimed to report the treatment steps in a 26-year male patient, presented with a class II div 1 incisor relationship on a class II skeletal base with increased vertical proportions. The case was complicated by missing lower second premolars and retained lower second deciduous molars. Severe crowding was evident in the lower arch with mild crowding in the upper arch. The overbite and the overjet were increased. Scissor bite was evident in the left buccal segment. Treatment involved extraction of upper first premolars and lower second deciduous molars, utilizing moderate anchorage using a preadjusted edgewise fixed appliance (0.022’’ X 0.028”) with Roth prescription. Treatment duration was 20 months in total. The envelope of discrepancy specifies strict rules when camouflaging class II cases. The ability to retract incisors and the use of class II mechanics are within limited range to avoid damage to the periodontium. The current case report showed that the ability of the clinician to retract incisors using TADs could be carried out with high rate of success and safety.

In-field dynamic response of instrumented wine tanks subjected to aftershock earthquakes

An experimental investigation of the dynamic behaviour of anchored flat-based wine storage tanks in a winery located in Marlborough, New Zealand is presented herein. Six wine storage tanks with different dimensions, capacities, and anchorage systems were instrumented with accelerometers for approximately six weeks following the 2016 Kaikōura earthquake, providing an opportunity to conduct a parametric study of their dynamic response when subjected to 37 aftershock earthquakes. The largest accelerations measured in the horizontal (X and Y) and vertical (Z) axes directions at the top of the six tanks occurred in conjunction with a Mw5.48 aftershock earthquake, with analysis indicating that the peak acceleration at the tank top occurred along the horizontal (Y) axis with a value of 0.545 g.Analysis of accelerations recorded at the top of the six tanks revealed that for low-intensity earthquake shaking the largest accelerations were measured at the top of the 40kL tank. A comparison of the tank instrumentation data indicated that the 175kL tank with a shear bolt anchorage system performed better than the nominally identical 175kL tank with a necked tension anchorage system, with the maximum lateral accelerations attained in the horizontal X and Y axes directions for the tank with the necked tension anchorage system being on average 1.59 times and 1.39 times the acceleration attained for the tank with the shear bolt anchorage system. Analysis of the results for the highest intensity earthquake shaking (Mw5.48) also indicated that the two tanks with installed energy dissipation systems sustained less acceleration when compared to tanks with a traditional anchorage system. Also, good agreement was observed between the values of the impulsive period attained from the analysis of the tank instrumentation data and from finite element (FE) modal analysis.

The Behavior of RC Beams Retrofitted with Carbon Fiber Reinforced Polymers (CFRP)

The need for the introduction of economical and quicker retrofitting techniques is increasing due to the ever-aging infrastructure and damages produced by major catastrophic events around the world. The application of Carbon Fiber Reinforced Polymers (CFRP) for strengthening and retrofitting of reinforced concrete structures is gaining popularity due to its higher strength, lightweight, durability, corrosion resistance, and aesthetic value. This study presents the results of two strengthened and two retrofitted beams in comparison to control specimens. Two specimens were strengthened and two were retrofitted by attaching CFRP (Sika Carbo-Dur S812 or Sika-Wrap 230C) to the tension side of the beams using high strength epoxy. The results show that one CFRP strip/wrap simply attached at the tension side can help the damaged beam regain/pass the original strength. All specimens fail due to debonding of CFRP from the concrete surface emphasizing the need for efficient anchorage systems. Among the four patterns adopted, CFRP strips along with u-shaped anchorages at the ends provided the highest strength enhancement of 17.36%.

Mechanical properties of rock bolt and analysis for the full-process of sliding failure based on rock mass absolute displacement

Previous studies rarely involved the mechanical properties of anchorage system under the condition of internal absolute displacement of surrounding rock and the solution of important parameters of anchorage system. In this paper, the absolute displacement law of rock mass under the anchorage system is analyzed by the fiber grating (FBG) multi-point displacement meter and multidirectional displacement conversion formula. Based on the coordinated deformation principle for rock bolt and rock mass, the mechanical analysis model for rock bolt-rock mass system is established, and the influence rules of rock bolt length, rock bolt diameter and rock bolt preload on the internal force distribution of rock bolt is studied based on the stress analysis of full-length rock bolt in a tunnel engineering. The results show that: (1) with the increase of rock bolt length, the anchoring effect gradually enhances, but the improvement degree decreases gradually; (2) with the increase of rock bolt diameter, the anchoring effect is enhanced; at the same time, however, the shear stress of rock bolt is larger, and the possibility of rock bolt sliding also increases; and (3) with the increase of preload, the increase of “anchor length” makes the anti-sliding ability of rock bolt increase correspondingly, and the supporting effect of rock bolt increases gradually. Then the full-process analysis for the mechanical mechanism of rock bolt sliding failure and the iterative calculation method for rock bolt displacement are studied. At last, the numerical simulation for pull-out test is carried out through the finite element analysis to verify the calculation results of mechanical model, and according to the iterative operation, the two important parameters such as the interface shear stiffness K and the interface peak shear strength τ P are solved. The analysis show that the numerical simulation results are in good agreement with the mechanical model calculation. This study can provide a theoretical basis for rock bolt support technology and support structure design. • The testing and calculation methods of absolute displacement law of rock mass are analyzed by the FBG. • The analytical expressions for the axial force and shear stress of full-length rock bolt are obtained. • The full-process analysis for the mechanical mechanism of rock bolt sliding failure is studied. • The iterative calculation method for rock bolt displacement is proposed.

FLEXURAL BEHAVIOR OF STEEL FIBER-REINFORCED LIGHTWEIGHT AGGREGATE CONCRETE BEAMS PRESTRESSED WITH CARBON FIBER-REINFORCED POLYMER BARS

An unbonded prestressing anchorage system for carbon fiber-reinforced polymer (CFRP) tendons was introduced. Eight lightweight aggregate concrete (LWC) beams prestressed with unbonded CFRP tendons which used CFRP auxiliary reinforcements and one fabricated using normal weight concrete (NWC) were tested under a four-point bending condition. The influences of concrete type, of prestressed degree and, of clear span length on the cracking moment, on the moment-deflection response and, on the crack width were analyzed. The existing deflection and crack width models for unbonded FRP prestressed beams with steel auxiliary reinforcements were modified from the view of equivalent axial stiffness. The applicability of the modified models was evaluated based on the test results. It is shown that the serviceability limit state of the beams is mainly governed by the crack width limit. The ratios between the moment at crack width of 0.5 mm and the ultimate moment range from 41% to 52%. With the same total reinforcement amount, the increase in the prestressed degree helps delay the cracking of the specimens. Increasing the amount of the auxiliary reinforcement and of the unbonded prestressed tendons both improve the beam stiffness and restrain the propagation of the cracks. The modified Cheng’s and modified Meng’s deflection models provide accurate deflection predictions for LWC beams with unbonded prestressed and auxiliary CFRP reinforcements.

Evaluation of stability of temporary anchorage devices for orthodontic treatment

Aim: The purpose of the present research was to assess the stability of temporary anchorage devices used in orthodontic treatment. Methodology: Freshly ovine mandibles were cut in blocks. Twenty-seven miniscrews (diameter 1.6 × 8 mm; G2, Dual Top Anchor System, Jeil Medical, Seoul, Korea) were inserted in the blocks and divided in 2 ex­perimental groups: single miniscrew and the innovated design “Seifi Twin Screw (STS)”. Primary stability was evaluated by Periotest “M”® device. Results: Independent t-test showed a significant difference between 2 experimental groups in periotest evaluation (p&lt; 0.05). STS demonstrated higher primary stability due to its mechanical configuration and design. Conclusion: The STS provides higher primary stability and was found to be effective in increased success rate of miniscrew systems from the standpoint of primary stability.

Effects of the anchor bolts and soil flexibility on the seismic response of cylindrical steel liquid storage tanks

When cylindrical tanks are subjected to strong seismic excitations, the main characteristic that they present is the partial uplifting of the base plate due to the hydrodynamic pressure on the tank walls. This partial base uplifting occurs in both unanchored and anchored tanks, and can provoke several types of failure. A comprehensive analysis of the tank base uplifting implies considering different non-linearity mechanisms. This paper presents a simple and efficient model that takes into consideration the effects produced at the tank base (i.e., uplifting and rocking), as well as, the soil flexibility and the nonlinear effects at anchor system. A comprehensive analysis of the soil–foundation–structure interaction effects, in conjunction with the influence of the convective part of the fluid, was carried out for three anchored cylindrical steel tanks subjected to lateral seismic loads. First, a sinusoidal ground motion was applied to the tanks and the response was discussed for a better understanding of the model capabilities and the soil–foundation–structure interaction. Later, a 3D dynamic analysis was carried out and the effect of considering or not considering the convective component was evaluated. Three seismic ground motion and four different soil flexibilities were considered. Finally, a sensitivity analysis considering different number of anchor bolts in addition to the soil–foundation–structure interaction was performed for the slender tank. The non-linear simplified model proposed in this study was able to obtain a good estimate for the rocking resistance, the anchor bolt effects (considering post-yielding and gap opening/closing at the tank–foundation interface), soil flexibility and the stress distribution on the tank walls. The obtained results allow a better understanding of the seismic response of anchored tanks and shows that the soil–foundation–structure interaction reduces critical response parameters. However, the energy dissipation caused by the anchoring system is low, therefore, response modified factor is not expected in thin walled cylindrical liquid storage tanks. Finally, a certain minimum number of anchors is required to avoid failure due to buckling or excessive uplift. These results can motivates possible modifications in current seismic design codes, where energy dissipation technologies could be considered explicitly as a very promising alternative.

Application of Bio-Active Elastin-like Polypeptide on Regulation of Human Mesenchymal Stem Cell Behavior

Regenerative medicine using stem cells offers promising strategies for treating a variety of degenerative diseases. Regulation of stem cell behavior and rejuvenate senescence are required for stem cells to be clinically effective. The extracellular matrix (ECM) components have a significant impact on the stem cell’s function and fate mimicking the local environment to maintain cells or generate a distinct phenotype. Here, human elastin-like polypeptide-based ECM-mimic biopolymer was designed by incorporating various cell-adhesion ligands, such as RGD and YIGSR. The significant effects of bioactive fusion ELPs named R-ELP, Y-ELP, and RY-ELP were analyzed for human bone-marrow-derived stem cell adhesion, proliferation, maintenance of stemness properties, and differentiation. Multivalent presentation of variable cell-adhesive ligands on RY-ELP polymers indeed promote efficient cell attachment and proliferation of human fibroblast cells dose-dependently. Similarly, surface modified with RY-ELP promoted strong mesenchymal stem cell (MSCs) attachment with greater focal adhesion (FA) complex formation at 6 h post-incubation. The rate of cell proliferation, migration, population doubling time, and collagen I deposition were significantly enhanced in the presence of RY-ELP compared with other fusion ELPs. Together, the expression of multipotent markers and differentiation capacity of MSCs remained unaffected, clearly demonstrating that stemness properties of MSCs were well preserved when cultured on a RY-ELP-modified surface. Hence, bioactive RY-ELP offers an anchorage support system and effectively induces stimulatory response to support stem cell proliferation.

CRITICAL FACTORS FOR FAILURE OF ORTHODONTIC MINI IMPLANT: A REVIEW

Anchorage in orthodontics is of prime importance for effective results. With the introduction of temporary anchorage devices (TADs) as skeletal anchorage method its use has been popularised. Although all anchorage systems have their own merits but they are often associated with certain demerits too. Since, literature is ooded with articles documenting the success rate but, as there are always two facets to everything, an insight to the failures of TADs should also be unravelled. So, review was done with the objective to evaluate the factors responsible for the failure of mini implants.Strategic and through search of the literature in four major databases was undertaken for data extraction and conclusion was drawn that mini implant failure is a multifactorial problem which includes mini implant related factors, clinician related factors and patient related factors.