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Ultimate Shear Force of an Any Anchor Group Post-Installed into Concrete
This paper is devoted to the fastening system that consists of a number of anchors of approximately equal effective embedment depth, called “anchor group”, embedded into hardened concrete, used to transmit forces transverse to the anchors from an attachment to the concrete. The anchor group is far from the edges and is subjected to no more than marginal axial forces. Being post-installed, rather than cast-in, the embedded end of each anchor is not hooked, and no nuts, washers, or plates are attached to the embedded shaft. The paper focuses on the transverse forces that can be transmitted across an anchor group from an attachment to the concrete. The paper provides an analytical model for predicting the maximum (ultimate) shear force that an anchor group can bear, thus called “shear strength”. The model hence allows the structural designer to predict the shear strength of an anchor group post-installed into concrete. The model is based on five mechanical assumptions, which were established from a wide-ranging numerical analysis. Model predictions turned out to be, on average, 20% lower than the results of experiments performed on cast-in anchor groups borrowed from literature. The comparison verifies model accuracy, considering that the tested anchor groups benefitted from the extra-strength furnished by nuts and washers attached to the embedded shaft. Model predictions were also compared to code provisions; the former resulted to be up to one third of the latter. The paper presents and comments those comparisons, as well as all mathematical development. Applications of the model to wide-ranging case studies is presented and discussed as well.
Journal Article
A breaking cat news adventure. Lupin leaps in
\"Picking up where they last left off in Breaking Cat News, are Elvis, Puck, and Lupin reporting on the breaking news that matters to cats. Cynical, no-nonsense Elvis and shy, sweet, sensitive Puck are the reporter kitties in the field, while the adventurous jokester Lupin serves as anchor cat. Together, they're back to break headlines on mysterious man \"tails,\" all things holiday-related, new cat friends, and all the daily happenings in and outside their home.\"--Publisher.
Book
Biomechanical comparison of different suture anchors used in rotator cuff repair surgery–all-suture anchors are equivalent to other suture anchors: a systematic review and network meta-analysis
Purpose
Suture anchors are commonly used to repair rotator cuff tendons in arthroscopy surgery, and several anchor materials have been created to maximize pull-out strength and minimize iatrogenic damage. We hypothesized that all-suture anchors have biomechanical properties equivalent to those of conventional anchors. Our purpose is to compare the biomechanical properties of different anchors used for rotator cuff repair.
Methods
The Embase, PubMed, Cochrane, and Scopus databases were searched for biomechanical studies on various suture anchors. The search keywords included rotator cuff tears and suture anchors, and two authors conducted study a selection, risk of bias assessment, and data extraction. The failure load, stiffness, and displacement were calculated using the mean differences with 95% confidence intervals (CIs). Failure modes were estimated using summary odds ratios with 95% CIs. The surface under the cumulative ranking curve was used for the relative ranking probabilities. A sensitivity analysis was performed by excluding studies using synthetic bones.
Results
The polyetheretherketone (PEEK) (
p
< 0.001) and all-suture anchors (
p
< 0.001) had higher failure loads than the biocomposite anchors, whereas no significant difference was observed in stiffness among the anchors. The all-suture (
p
= 0.006) and biocomposite anchors (
p
< 0.001) had displacements higher than the metal anchors. The relative ranking of the included anchors in failure loads and displacement changed in sensitivity analysis. The meta-analysis did not find significant differences, but the relative ranking probabilities suggested that all-suture anchor had a higher rate of anchor pull-out and a lower rate of eyelet or suture breakage. In contrast, the metal anchors were associated with a higher number of eyelet breakage episodes.
Conclusions
All-suture anchors showed significantly higher failure loads than the biocomposite anchors and similar cyclic displacements to the biocomposite and PEEK anchors. There were no significant differences in stiffness between all-suture and conventional suture anchors. The relative ranking of biomechanical properties changed in sensitivity analysis, suggesting the potential effect of bone marrow density.
Level of Evidence
Level IV.
Journal Article
Pullout capacity of multi-plate horizontal anchors in sand: an experimental study
A horizontal anchor is a structural member designed to resist the vertical pullout forces and ensure the stability of structures like the tower foundations, masts and bridges. This paper focuses on the experimental study for the estimation of the ultimate pullout capacity of multi-plate horizontal anchors embedded in the sand. The tensile load of a structure is resisted by the multi-plate anchors using the many plates connected along the central shaft. The multi-plate anchors would be capable of generating higher pullout capacity in comparison with the single-plate anchors, for an embedment depth considered. The pullout capacity is generative of the inherent structure of the multiple plates encompassing multiple layers of sand. The paper presents a comparison of the multi-plate anchors with the existing studies of single-plate anchors. Results show the multi-plate anchor replacing the existing single-plate anchors efficiently. Few of the primary conclusions are (a) the increase in the pullout capacity of the double-plate and triple-plate anchors with the increase in the embedment ratio, (b) the critical embedment ratio being indicative of a transition of the failure mechanism developing for shallow and deep anchors, (c) a decreasing pullout capacity for shallow multi-plate anchors in comparison with the single-plate anchors, and (d) an increasing pullout capacity for deep multi-plate anchors in comparison with the single-plate anchors. The paper provides a brief discussion on the scale effect, the effect of spacing, the effect of the shape of the anchors on the pullout capacity.
Journal Article
Katie Couric : groundbreaking TV journalist
A biography of the television journalist, Katie Couric.
Book
A Unified Model for Analyzing Comprehensive Behaviors of Deepwater Anchors
Anchors may exhibit various complicated behaviors in the seabed, especially for deepwater anchors including gravity installed anchors (GIAs) and drag embedment plate anchors (drag anchors), stimulating the development of an efficient analytical tool that applies to a variety of anchors. The present paper introduces a unified model for analyzing different anchor behaviors in both clay and sand, consisting of unified concepts, mechanical models, and analytical procedure. The kinematic behaviors of the anchors are classified uniformly as three types, i.e., diving, pulling out, and keying. By utilizing the least-force principle, various anchor properties, such as the ultimate pullout capacity (UPC), failure mode, movement direction, embedment loss, and kinematic trajectory, can all be determined by the combination and analysis of the three behaviors. Applications of the model are demonstrated summarily, by solving the UPC and the failure mode of anchor piles and suction anchors, the kinematic trajectory of drag anchors in a single soil layer or layered soils, the maximum embedment loss (MEL) of suction embedded plate anchors (SEPLAs) and OMNI-Max anchors, and the kinematic behavior of OMNI-Max anchors. Compared to existing theoretical methods, this unified model shows strong applicability and potentiality in solving a variety of behaviors and properties of different anchors under complicated seabed conditions.
Journal Article
Study on the influence of anchor plate parameters on the bearing characteristics of the new large-diameter multi-plate soil anchor and creep property of anchor
The existing mechanical and grouting anchors mostly use the expansion shell method to form a cavity on the borehole wall, and the cement slurry is poured to form multiple enlarged head plates, but the operation is more difficult and the diameter of the formed plate is smaller. In this paper, a new type of large-diameter multi-plate soil anchor and its reaming cavity forming tool are proposed, which can make the operation easier and form a large-diameter enlarged head plate. In order to study the influence of the diameter of anchor plate, the number of anchor plates and the spacing of anchor plates on the vertical uplift capacity of the large-diameter multi-plate soil anchor, 25 sets of comparative models were established for simulation analysis. The finite difference method of FLAC
3D
software is used to simulate the model. It is found that when the length of the anchor is 6 m and the diameter of the anchor rod body is 150 mm, the optimal diameter of the anchor plate of the large diameter multi-plate soil anchor is 590 mm, the optimal number of anchor plates is 6, and the optimal anchor plate spacing is 800 mm, which means the action range of the anchor plate on the lower soil is about 5 times the diameter of the bolt. When the number of anchor plates is too small or the spacing between anchor plates is too large, the structural advantages of large-diameter multi-plate soil anchor cannot be fully utilized, resulting in a decrease in the ultimate uplift capacity. When the number of anchor plates is too large or the spacing between anchor plates is too small, the stress superposition effect occurs in the soil, and the through shear failure occurs, which leads to the decline of the ultimate uplift capacity. Under the condition that the number of anchor plates and the spacing of anchor plates are fixed, the larger the diameter of the anchor plate is, the larger the ultimate pull-out capacity of the large-diameter multi-plate soil anchor is, the smaller the vertical failure displacement of the anchor head is, but the increase of the uplift capacity is gradually reduced. The creep rate of the new large-diameter multi-plate soil anchor bolt is 0.91 mm, and the creep rate of equal-diameter soil anchor bolt is 1.69 mm. It is verified that the new large-diameter multi-plate soil anchor can be effectively applied to various projects.
Journal Article
Element-scale pullout test study on the mechanical behavior of grouted anchor–soil interface subjected to ground pressure
The soil–anchor interface mechanical behavior is of practical importance for the bearing performance of ground anchors. Element-scale pullout test is a simple, reliable, and economical technique to investigate the interface shear stress–displacement response of anchors. However, the influence range of boundary effect for the anchoring element-scale pullout specimens is poorly understood, particularly under the actual stress and construction conditions. In addition, there is still a lack of study on the mechanical behavior of soil–anchor interface subjected to ground pressure via element-scale pullout test. In this paper, an element-scale pullout test setup that can simulate ground pressure and construction method of ground anchors was specially developed, with details introduced carefully. A response surface function-based soil dry density prediction model was proposed for the test design. Comparison with the soil consolidation test results indicates that this model equipped with high fitting and prediction accuracy. Twenty groups of element-scale pullout tests with different ground pressures and anchor diameters were conducted. Based on the test design of the proposed model, the soil density and moisture content were almost the same for all specimens after consolidation. The shrinkage of anchor hole, interface shear stress–displacement response, and interface shear strength were discussed adequately. It is shown that the soil–anchor interface shear strength is hardly dependent on ground pressure under the actual construction method of anchors. The influence of boundary effect for the element-scale pullout test can almost be eliminated when diameter ratio of specimen to anchor exceeds 5.0 ~ 6.7.
Journal Article