Anchor Test Research Articles

Anchor test and long-term monitoring of grouted anchors instrumented with Fiber Bragg Grating sensing technology

Geotechnical monitoring of anchors provides fundamental data for analysis and evaluation to ensure safe environment. The use of optic fiber sensing technology, especially Fiber Bragg Gratings, brings many advantages of optic fiber sensors, such as high measurement accuracy, real-time continualmonitoring of deformation, on-line access to data and resistance against electromagnetic interferences. This article deals with anchor tests instrumented with FBG deformation gauges of the root and the tendon of the pre-stressed strand anchor in a test field in the Central Bohemian Region. First, the anchor with three optic cables with FBG sensors for measurement of axial deformation was subjected to six loading stages of the anchor test. Most of the sensors measured values of axial deformation less than 200 με and the root mobilisation was observed. Then, the measurement continued by 26-day long-term monitoring and a trend of a small increase of deformations occurred.

Comparison of 1g and centrifuge modelling of drag anchors with subsurface wireless tracking

The kinematic behaviour of drag embedment anchors has become a recent research focus due to the increase in offshore renewable energy devices. This is due to their potential use as an anchoring system for future floating wind applications, in addition to the need to understand their penetration behaviour as a part of the Cable Burial Risk Assessment. Studies on the behaviour of anchors typically consist of field scale or model centrifuge tests, where such facilities are not readily available to all and can result in significant cost. In addition to this, measuring the load–penetration behaviour of an anchor has proven to be a significant challenge, as any contact-based methods are likely to influence the penetration behaviour of the anchor. In this paper, a novel wireless method of recording the inclination of the anchor and calculating the penetration depth is presented. A comparison of the penetration behaviour of a Class F (AC-14) anchor has been made in sand using centrifuge and 1g model scale testing. The results indicate that the 1g testing can match the behaviour of the anchor testing in the centrifuge in terms of both the position of the anchor and its orientation during the dragging event.

A Modified Bearing Capacity Model for Inclined Shallow Anchor Cable with Experimental Verification

Most theoretical models of shallow anchor cables do not take the effect of anchor inclination into consideration, which is an important factor influencing load distribution, stress concentration, and failure mechanisms. In this paper, a modified bearing capacity was developed for a single anchor cable, taking the anchor inclination into consideration, based on the principle of limit equilibrium. Then, a series of indoor pull-out tests of single anchors with different inclinations were performed, where the effects of the anchor inclination on the bearing capacity and failure mechanisms were carefully analyzed. The experimental bearing capacities were compared to the predicted data of the proposed modified model, as well as other existing experimental results, aiming to verify the applicability and accuracy. The results show that the bearing capacity increases with decreasing anchor inclination because the vertical component of the force acting on the anchor cable increases. The failure models of the anchor cables, pulled out at different angles, exhibit an asymmetric “inverted trumpet” shape, which is caused by the varying stress distributions around the anchor cable during pull-out. In addition, the bearing capacities of the theory differ very little from the experimental and previous results, with a max error of nearly 10%. This study confirms that the proposed model reliably captures the effects of anchor inclination, providing valuable insights for designing inclined anchors in engineering practice.

Musculoskeletal mimics for lumbosacral radiculopathy. Part 1: Theoretical considerations.

The diagnosis of lumbosacral radiculopathy includes the exclusion of common musculoskeletal conditions that can cause similar symptoms. Neurology and physiatry physicians use history taking and physical examination findings to develop a differential diagnosis. Appropriate diagnostic testing is then utilized to narrow down this differential diagnosis to determine a working hypothesis of the cause of a patient's symptoms, leading to a treatment plan. There are stark limitations of patient symptoms and physical examination findings in making the diagnosis of lumbosacral radiculopathy and added value of a combination of symptoms and signs to distinguish patients with lumbosacral radiculopathy from patients with mimic disorders. Diagnostic tests have variable strengths and limitations in helping to confirm this diagnosis, contrasting the high sensitivity and lower specificity of magnetic resonance imaging (MRI) with the high specificity but lower sensitivity of electromyography (EMG). Further complexity is added to the task of making a diagnosis and setting a treatment plan by the fact that these disorders are common and interact with each other; they are present concomitantly in up to 25% of patients presenting for electrodiagnostic evaluation. A companion paper will review common musculoskeletal mimics of lumbosacral radiculopathy and provide tools to anchor testing for those conditions to the traditional neurological evaluation of lumbosacral radiculopathy.

Field pullout test and anchorage length calculation for external anchorage of GFRP anti-floating anchors

Field pullout destructive tests of GFRP anti-floating anchors with different anchorage lengths and different anchorage forms are carried out on inverted foundation slabs. Explore the damage patterns and anchorage mechanisms of bent anchors, straight anchors and GFRP anchors with different bending configurations in relation to the concrete foundation slab. Calculate the reasonable anchorage length of anti-floating anchors. The test results show that the straight line anchor rod and bent anchor rod are mainly damaged by sliding. The displacement of anchor rod body decreases with the increase of anchorage length, bending radius and bending length. The bending treatment of anchor rods reduces the pullout bearing capacity of GFRP anti-floating anchors, but it can significantly reduce the rod displacement. The longer the length of the bent section of the anchor rod body and the larger the bending radius, the lower the strength utilization of the anchor rod body. Through the calculation of the test results of different anchorage length anti-floating anchor rods, it is found that the current calculation method for the basic anchorage length of anchor rods is too conservative. For the actual anti-floating project, a more reasonable anchorage length calculation method is proposed, and the reasonable anchorage length of anchor rods for this test condition is 370–530 mm.

Rock anchor testing on sandstone from the Botucatu Formation, Paraná River Basin, Brazil: Insights for climbing safety procedures at the Corumbataí Geopark Project

The Corumbataí Geopark Project, located in São Paulo state, southeast Brazil, features valuable geosites that represent Earth's heritage and attract visitors with geoturism activities such as climbing. Rock anchors are crucial for ensuring climbers' safety in case of falls. This study reveals that the load capacity performance of expansion rock anchors is influenced by the applied torque, the physical-mechanical properties of the rock, and the weathering-induced strength degradation over time. The sandstone of Botucatu Formation, the predominant lithotype at these geosites, was assessed through petrographic analysis, non-destructive testing, physical and mechanical assessments, and pull-out tests of the anchors. Our findings indicate that the sandstone generally meets the geotechnical properties requirements for load capacities outlined in international climbing guidelines, a threshold of 80 MPa is recommended for effective rock anchor performance. However, prolonged exposure leads to rock degradation, compromising safety. Consequently, anchors should not be used in weathered rock and regular maintenance is strong recommended for climbing safety, approximately every 6 six years. This study provides a novel approach to characterizing rock-anchor interactions, supporting the development of effective management plans for outdoor activities.

Assessing Population Invariance of 2021 Agricultural Science Examination of National Examination Council (NECO) in North Central Nigeria

Purpose: This study examines the challenges and implications of equating scores from different test forms, focusing on the 2021 NECO Agricultural Science examinations in North Central Nigeria. It considers factors such as school location, school type (public vs. private), and test administration (internal vs. external) to evaluate the extent to which these equated scores maintain invariance across different populations. Methodology: The study employs a non-equivalent anchor test (NEAT) group equating design and analyzes data from a population of 97,413 Senior Secondary students using the IRT statistical tool. Findings: The key findings reveal significant disparities in the equated scores between internal and external examinations, as well as between urban and rural locations. These discrepancies challenge the fairness and comparability of the examinations, raising concerns about potential biases and inequities in educational assessment. Significance: The research highlights the importance of achieving population invariance in test equating methodologies. It recommends adopting efficient equating methods, such as mean equating, and utilizing the Item Response Theory (IRT) approach for standardized test development to ensure fairness and equity in educational evaluations.

Aggregate Type and Concrete Age Effects on Anchor Breakout Performance: Large Database and Insights

This contribution summarizes the largest available literature data collection on tensile and shear loaded anchor tests, obtained in two independent studies and performed by two different research groups. It was the objective of the two studies to investigate a possible effect that petrographically different coarse aggregate types may have on the tensile and shear load capacity for concrete breakout failure modes. In total, seven normal-strength and four high-strength concretes were tested at two different ages. Structural tests were performed on cast-in (tensile and shear tests) and post-installed adhesive anchors (shear tests). Parallel to the structural tests, each concrete was characterized in terms of compressive and tensile strength. Finally, the combined experimental data offer novel insights into the predictive quality of available design models for concrete cone capacity in tension and edge breakout in shear with respect to a potential aggregate effect. Systematic analyses indicate only minor aggregate effects after normalization by compressive strength (less than 7% difference between normalized values). However, the study reveals potential curing and concrete age effects where a 9% increase in predicted values is shown when concrete cures longer. The predictive equations remain conservative in comparison to all the investigated properties and their validity is shown in this study.

Enhancing music recognition using deep learning-powered source separation technology for cochlear implant users.

Cochlear implant (CI) is currently the vital technological device for assisting deaf patients in hearing sounds and greatly enhances their sound listening appreciation. Unfortunately, it performs poorly for music listening because of the insufficient number of electrodes and inaccurate identification of music features. Therefore, this study applied source separation technology with a self-adjustment function to enhance the music listening benefits for CI users. In the objective analysis method, this study showed that the results of the source-to-distortion, source-to-interference, and source-to-artifact ratios were 4.88, 5.92, and 15.28 dB, respectively, and significantly better than the Demucs baseline model. For the subjective analysis method, it scored higher than the traditional baseline method VIR6 (vocal to instrument ratio, 6 dB) by approximately 28.1 and 26.4 (out of 100) in the multi-stimulus test with hidden reference and anchor test, respectively. The experimental results showed that the proposed method can benefit CI users in identifying music in a live concert, and the personal self-fitting signal separation method had better results than any other default baselines (vocal to instrument ratio of 6 dB or vocal to instrument ratio of 0 dB) did. This finding suggests that the proposed system is a potential method for enhancing the music listening benefits for CI users.

Feasibility Study of Steel Derailment Containment Provisions through Quasi-Static Experiments

Railway derailments present a safety hazard, carrying the potential for severe consequences for both human lives and the economy. Implementing derailment containment provisions (DCPs) near the track centerline is essential for mitigating risks in operating high-speed rail (HSR) while providing significant advantages for the large-scale upgrade of existing railway infrastructure. Therefore, this paper investigated the feasibility of a DCP system made of steel through quasi-static experiments, aiming to enhance safety in HSR operations. Initially, single anchor tests were conducted to assess its capacity to withstand applied loads, prevent the pullout of steel anchors, and avoid the local rotation of the steel frame. Then, full-scale steel DCP systems were manufactured and tested for quasi-static load at different locations, including the mid-anchor, the mid-span, and the end-anchor. The relationship between applied load and displacement, along with the initial stiffness of the DCP specimens, was discussed. The findings revealed that the single anchor can withstand an applied load of up to 197.9 kN. The DCP specimen maintained structural integrity at the 207 kN target load under all load scenarios, showing a maximum displacement of 8.93 mm in the case of applied load at mid-span. Furthermore, the initial stiffness of the DCP systems was 1.77 to 2.55 times greater than that of a single anchor, validating a force-bearing coordination mechanism among neighboring anchors and the substantial impact of the applied load positions on their stiffness.

Behavior of a Rock Mass in Uplift Field Tests of Rock Anchors

AbstractRock anchors are high-capacity reinforcement measures used to stabilize large-scale infrastructures. According to the literature, they can fail in one of the four ways: (1) steel tensile failure; (2) tendon–grout interface failure; (3) grout–rock interface failure; and (4) rock mass uplift failure. Rock mass uplift field tests were performed in a limestone quarry to test this fourth failure mode. The tests were designed to induce rock mass failure around rock anchors. The ground surface heaved asymmetrically around the anchors and the pre-existing joints in the rock mass tended to open first. The seismic activity in the rock mass was greatest close to the anchor, decreasing with distance. The failure crater in the rock followed the joint sets in the rock mass, and the shape was partly controlled by the pre-existing joints. The apex angle of the failures was measured to be between 125 and 140$$^{\circ }$$ ∘ . The horizontal stress in the rock mass increased when the anchor was pulled, indicating load arching around the anchor. The observed failure was a combination of rock mass uplift and grout–rock bond failure. The measured anchor capacity was much higher than the estimated rock mass capacity using the recommended design methods of the Norwegian Public Roads Administration.

Efficiency Analysis of Item Response Theory Kernel Equating for Mixed-Format Tests.

This study aims to evaluate the performance of Item Response Theory (IRT) kernel equating in the context of mixed-format tests by comparing it to IRT observed score equating and kernel equating with log-linear presmoothing. Comparisons were made through both simulations and real data applications, under both equivalent groups (EG) and non-equivalent groups with anchor test (NEAT) sampling designs. To prevent bias towards IRT methods, data were simulated with and without the use of IRT models. The results suggest that the difference between IRT kernel equating and IRT observed score equating is minimal, both in terms of the equated scores and their standard errors. The application of IRT models for presmoothing yielded smaller standard error of equating than the log-linear presmoothing approach. When test data were generated using IRT models, IRT-based methods proved less biased than log-linear kernel equating. However, when data were simulated without IRT models, log-linear kernel equating showed less bias. Overall, IRT kernel equating shows great promise when equating mixed-format tests.

Study on the anchoring performance and failure mechanism of basalt/glass hybrid fiber reinforced plastic anchors in coupled environment

AbstractTo investigate the real anchorage performance of basalt and glass hybrid fiber reinforced plastic (FRP) anchors in external corrosive environments. In this paper, a combination of experimental studies and finite element analysis was used. By carrying out pull‐out tests of basalt and glass hybrid FRP anchors under the synergistic effect of freeze–thaw cycles and alkaline environment, the effects of factors such as hole diameter, anchorage length, and mortar strength on their anchorage performance and durability were investigated. Critical corrosion time was introduced to determine the degree of corrosion of the anchor rods. After that, it combined with numerical simulation to reveal the degradation mechanism of the anchorage performance of hybrid anchors. The results showed that the best anchorage performance of basalt/glass hybrid FRP anchors was achieved when the hole diameter was 24 mm, the anchorage length was 175 mm, and the mortar strength was 45.5 MPa. The ultimate pull‐out load was up to 122.16 kN. When the time did not exceed the critical corrosion time, the ultimate load‐carrying capacity of basalt and glass hybrid FRP anchors increased by 9.3% compared to the uncorroded environment. Beyond the critical corrosion time, the ultimate load‐carrying capacity was reduced by 23.3% and the anchorage performance was degraded. In addition, the contact interface between the anchor and the mortar is the weak area of the anchoring structure, which should be focused on in the later design of the actual project.Highlights Basalt/glass hybrid FRP anchors have good corrosion resistance. The anchoring performance of hybrid FRP anchors under the coupled environment is studied. Hole diameter and anchoring length have more influence on the anchor performance. The concept of critical corrosion time is put forward. The failure mechanism and coupling environment influence are revealed by FES.

Full-scale pullout tests of rock anchors in a limestone quarry focusing on bond failure at the anchor-grout and grout-rock interfaces

Full-scale pullout tests of rock anchors in a limestone quarry focusing on bond failure at the anchor-grout and grout-rock interfaces

A Comparison of Covariates, Equating Designs, and Methods in Equating TIMSS 2019 Science Tests

This research aimed to compare the equated scores by the methods based on classical test theory (CTT) and kernel equating, using covariates design (NEC) and anchor test design (NEAT). TIMSS 2019 science test scores equated by both Tucker, Levine true score, Levine observed score, equipercentile equating (pre-smoothing and post-smoothing) methods in CTT, and linear and equipercentile methods in kernel equating. Additionally, the covariates in NEC design were “home resources for learning,” “student confidence in science and mathematics,” “like learning science,” “instructional clarity in science lessons,” “math achievement,” “sex,” and “speaking the language of the test at home”. The equating results in NEC were compared with those in NEAT and EG. The participants comprised 1699 4th-grade students who attended the e-TIMSS 2019 in Canada, Singapore, and Chile. Results were analyzed according to equating errors and differences between equated scores. The research concluded that math achievement and home resources for learning could be used as covariates in NEC to equate the science test in case equating could not be done in the NEAT. However, when the other variables were used as covariates in NEC, the equated scores were very similar to the EG. Also, Tucker (CTT) and post-stratification (kernel) yielded similar equated scores in linear equating, and these methods were similarly different from kernel linear equating in EG. In equipercentile equating, the equated scores obtained from the post-smoothing (CTT) and EG were close to each other but slightly differed from post-stratification.

Empirical ensemble equating under the NEAT design inspired by machine learning ideology

This study proposes an empirical ensemble equating (3E) approach that collectively selects, adopts, weighs, and combines outputs from different sources to take and combine advantage of equating techniques in various score intervals. The ensemble idea was demonstrated and tailored to the Non-Equivalent groups with Anchor Test (NEAT) equating. A simulation study based on several published settings was conducted. Three outcome measures – average bias, its absolute value, and root mean square difference – were used to evaluate the selected methods’ performance. The 3E approach outperformed other counterparts in most given conditions, while the cautions, such as tuning weights and assuming possible scenarios for using the proposed approach were also addressed.

Design bond stress parameters for rock anchors in Brisbane

Little published information is available on bond stress parameters at the grout-ground interface for the design of ground anchors within Brisbane rocks. In the absence of data, a designer will typically fall back to ‘universal’ correlations with measurable parameters such as Uniaxial Compressive Strength (UCS) or descriptions of rock type to nominate design bond stress values. In doing so, there is often little understanding of the limitations of such correlations or how applicable those correlations are for the rocks encountered within the local region. A study of Proof Test data from testing of sacrificial ground anchors constructed within materials from the Brisbane Tuff and Neranleigh Fernvale Beds Stratigraphic Units for an infrastructure project in Brisbane has been carried out to consider bond stress values at the grout-ground interface. Materials within the bond zone of ground anchors constructed in Brisbane Tuff and Neranleigh Fernvale Beds units have been classified into different rock units based on rock substance strength and Geological Strength Index. Details of anchor construction and testing procedures are presented, together with the adopted approach to test interpretation. Data from Proof Testing of ground anchors bonded into these materials is then interpreted and evaluated for each unit, with relationships developed for each rock type for ultimate and yield bond stress values at the grout-ground interface as a function of rock substance strength (UCS) and rock mass strength (based on Hoek and Brown,2018). For both rock types, grout-ground interface bond stresses increase with rock strength and quality, with better correlations evident based on rock mass strength than for UCS data. Comparisons of the interpreted bond stress relationships based on UCS are made for both rock types to published information for ground anchors and shaft adhesion parameters for cast-in-situ piles. Suggestions are made for amendments to the Proof Anchor test method to reduce the potential for premature termination of the test and consequent underestimation of the bond stress, and to obtain consistency between Proof and Production test methods.

Practical Considerations in Choosing an Anchor Test Form for Equating Under the Random Groups Design

ABSTRACT Careful considerations are necessary when there is a need to choose an anchor test form from a list of old test forms for equating under the random groups design. The choice of the anchor form potentially affects the accuracy of equated scores on new test forms. Few guidelines, however, can be found in the literature on choosing the anchor form. Five indices were proposed in this study to aid the selection and their performances were evaluated through a real-data-based simulation. The results shed some light on how to choose an anchor form in practice.

Equating Oral Reading Fluency Scores: A Model-Based Approach.

Words read correctly per minute (WCPM) is the reporting score metric in oral reading fluency (ORF) assessments, which is popularly utilized as part of curriculum-based measurements to screen at-risk readers and to monitor progress of students who receive interventions. Just like other types of assessments with multiple forms, equating would be necessary when WCPM scores are obtained from multiple ORF passages to be compared both between and within students. This article proposes a model-based approach for equating WCPM scores. A simulation study was conducted to evaluate the performance of the model-based equating approach along with some observed-score equating methods with external anchor test design.

Experimental and Theoretical Research on the Bearing Mechanism of Group Anchors in Sand

To investigate the bearing mechanism and efficiency of group anchors in sand, upward pulling tests of model group anchors were carried out for different conditions of the sand density, anchor burial depth ratio, and anchor spacing. The results show that the load-displacement relationships for group anchors is similar to that for single anchors, both being nonlinear for the same relative density and embedment ratio. The load-carrying capacity of group anchors is not a simple superposition of the capacities of two single anchors, but has a clear superposition effect, depending on the relative density, embedment ratio, and anchor spacing. The load carrying capacity increases with the anchor spacing up to a limiting critical value. The bearing mechanism of group anchors was qualitatively analyzed and quantitatively characterized using the strain field and shear stress field obtained through the digital image correlation. Adopting the test data and theoretical derivation, a critical anchor spacing equation is proposed and the relationship between critical anchor spacing, embedment ratio, and relative density is quantitatively characterized. Theory is proposed for predicting the group efficiency of group anchors with different configurations. Comparisons between the results of the developed model and experimental results reported in the literature show good agreement.