theA Research Articles

Egg structure of five antarctoperlarian stoneflies (Insecta: Plecoptera, Antarctoperlaria)

The egg structures of five antarctoperlarian species – Stenoperla prasina of Eustheniidae; Austroperla cyrene of Austroperlidae; and Zelandobius truncus, Megaleptoperla grandis, and Acroperla trivacuata of Gripopterygidae, were examined in detail, and the groundplan of the egg structure was considered within the representative lineages of Antarctoperlaria and Plecoptera. The flattened egg shape and the circular arrangement of micropyles along the equator are regarded as potential autapomorphies for not only Eustheniidae but also for Eusthenioidea. Austroperlidae has eggs with thin, less-sclerotized chorion, a gelatinous layer on the surface, and micropyles roughly and randomly arranged along the equator. A significant ultrastructural difference between the attachment disc in Gripopterygidae and the anchor plate of arctoperlarian Systellognatha suggests that these structures were independently derived. The thin less-sclerotized chorion represents a groundplan feature in Plecoptera, along with micropyles arranged in a circle, including those circularly arranged along the equator of the egg. On the other hand, in contrast to previous understanding, the sclerotized hard chorion is regarded as a derived feature, having been independently acquired in each of Eustheniidae and Gripopterygidae of Antarctoperlaria and Systellognatha of Arctoperlaria.

Discussion of “Numerical Investigation of Uplift Behavior of Circular Plate Anchors in Uniform Sand” by Nabil Al Hakeem and Charles Aubeny

Discussion of “Numerical Investigation of Uplift Behavior of Circular Plate Anchors in Uniform Sand” by Nabil Al Hakeem and Charles Aubeny

Closure to “Numerical Investigation of Uplift Behavior of Circular Plate Anchors in Uniform Sand” by Nabil Al Hakeem and Charles Aubeny

Closure to “Numerical Investigation of Uplift Behavior of Circular Plate Anchors in Uniform Sand” by Nabil Al Hakeem and Charles Aubeny

Discussion of “Pullout Behavior of Geocell-Reinforced Vertical Plate Anchors under Lateral Loading” by Sujit Kumar Dash and Awdhesh Kumar Choudhary

Discussion of “Pullout Behavior of Geocell-Reinforced Vertical Plate Anchors under Lateral Loading” by Sujit Kumar Dash and Awdhesh Kumar Choudhary

Closure to “Pullout Behavior of Geocell-Reinforced Vertical Plate Anchors under Lateral Loading” by Sujit Kumar Dash and Awdhesh Kumar Choudhary

Closure to “Pullout Behavior of Geocell-Reinforced Vertical Plate Anchors under Lateral Loading” by Sujit Kumar Dash and Awdhesh Kumar Choudhary

Free-Fall Penetration Behaviors of A New Dynamically Installed Plate Anchor in Marine Clay

A new dynamically installed plate anchor, the Flying Wing Anchor®, has been developed as a sustainable anchor concept for deep-water offshore wind turbines. The anchor is firstly installed by free-fall penetration and then followed by drag embedment. If the anchor is subjected to environmental loads, it dives deeper to mobilize a higher capacity. This study presents a series of free-fall penetration tests with model anchors in different weights to assess the anchor behavior during the free-fall penetration performance in one-layer soil with a constant shear strength profile. Anchor velocities and embedment depths were measured by a magnetometer. An energy-based model and a force-based model were calibrated against the test results of model anchors with different weights. Based on the calibrated force-based model, a series of design charts were developed to estimate the embedment depth of anchors in different sizes and with different impact velocities in various marine clays. The framework to plot design charts presented herein can be potentially applied to other dynamically installed anchors to predict embedment depth in engineering practice.

BEM-ALEM Modeling of Plate–Soil Interaction for Rigid Circular Foundation in Layered Saturated Soils Subjected to Mechanical or Thermal Load

AbstractCircular plate foundation is an essential foundation in the engineering of marine anchor plates, oil storage tanks, and cell towers. These circular plates are usually treated as the rigid c...

Normally loaded inclined strip anchors in cohesionless soil

Plate anchors are among the most effective anchorage systems that are widely used to resist horizontal and inclined uplift loads in many offshore and onshore applications. Previous research on plate anchors has largely focused on the horizontal or vertical breakout problems, with limited attention directed towards obtaining a full characterization of the effects of anchor orientation angle. The present study utilizes displacement-based finite element analyses to investigate the stability and performance of strip anchor embedded in cohesionless soil for plate inclination angles ranging from 0° to 90° from horizontal, where the applied load is normal to and acts at the center of the plate. This study investigates the effects of scale and roughness, along with the geometry of the failure mechanism for various plate orientations and embedment depths. The analyses, presented in terms of a non-dimensional breakout factor Nq, show that the breakout factor increases significantly with an increase in the inclination, especially for angles greater than 45° in loose sand and greater than 60° in dense sand. The analyses also show that scale effects (anchor width) can affect capacity. Finite element analyses have been used to introduce simple design charts relating the breakout factor to the embedment depth and relative density. Comparisons to experimental and numerical studies showed good agreement.

Primer registro del pepino de mar garra de león Euapta godeffroyi Semper, 1868 (Holothuroidea: Apodida: Synaptidae) en la isla Gorgona, Pacífico colombiano

Los holotúridos corresponden a 20-25 % de todas las especies conocidas de equinodermos. En el Pacífico colombiano se han registrado 34 especies, de las cuales 11 lo han sido en la isla Gorgona. Este es el primer registro del pepino de mar garra de león Euapta godeffroyi en la isla. El espécimen fue recolectado mediante buceo autónomo en el submareal del parche coralino conocido localmente como El Arrecifito del Muelle, a una profundidad aproximada de 2 m. Tenía una longitud aproximada de 80 cm y entre 2 y 3 cm de diámetro. Los osículos de la pared del cuerpo corresponden básicamente a anclas y a placas de anclas; estas últimas presentan pequeñas ramificaciones en la base del eje central. El presente registro llena un vacío en la distribución de esta especie en el Pacífico Oriental Tropical.

A folding-shank gravity installed anchor and its hydrodynamic characteristics in water: Physical modelling

The light-weight gravity installed plate anchor (L-GIPLA) is a plate-shaped anchor for securing offshore floating structures, which is dynamically installed with the aid of a booster. Therefore, it is necessary to investigate the hydrodynamic characteristics of the hybrid anchor (L-GIPLA + booster) during free fall in water. Model tests are conducted in the present study to investigate the drag coefficient and directional stability of the L-GIPLA and the corresponding hybrid anchor. On the basis of model testing results, the geometry of the L-GIPLA is optimised with tapered fluke with round-grinded edge and folding shank. It is verified by model tests that the modified anchor with folding shank is favourable for improving the directional stability and reducing the drag coefficient for the hybrid anchor. In order to mitigate the effect of the mooring line on the directional stability of the hybrid anchor, an arched fin or fan-shaped plate is set at the rear of the hybrid anchor in the direction opposite the shank to balance the drag force on the mooring line.

(The Interactive Effect between Fermentation with Trichoderma reesei on Ammoniation on Fiber Component of Sugar Palm Pulp

The purpose of this research was to examine the combination effect of fermentation time by Trichoderma reesei and ammoniation on fiber component of sugar palm pulp. The research used sugar palm pulp from Boyolali which was sun-dried. Sugar palm pulp fermentation with Trichoderma reesei requires nitrogen for microbial growth. Ammoniation process could loose lignocellulosic bonds and provides the nitrogen supply for Trichoderma reesei, therefore these treatments could optimize Trichoderma reesei in the fermentation process. Samples were fermented for 0, 3 and 6 days with 1,5% Trichoderma reesei. The research treatments were allocated according to a completely randomize design with pattern of 2x3 factorial. First factor was ammoniation treatment and second factor was variation of fermentation time. The parameters observedd were NDF, ADF, hemicellulose, cellulose and lignin. Research result showed that there is was no interactive effect between treatments on reducing levels of NDF and ADF, but interaction treatments decreased (P<0.05) levels of, cellulose and lignin. In conclusion, the interactive effet between fermentation time with Trichoderma reesei and ammoniation reduce levels of hemicellulose, cellulose and lignin in sugar palm pulp.

Design and numerical analyses of high-fill slope strengthened by frame with prestressed anchor-plates

Design and numerical analyses of high-fill slope strengthened by frame with prestressed anchor-plates

Large-scale testing and finite-element simulation of twin square anchor plates embedded at shallow depth in layered soil media

The motivation and scope of the present work are to investigate the interaction phenomenon of two closely spaced square plate anchors through physical modelling and validating it with the help of finite-element modelling. In the present study, different sizes of plate anchors are considered for studying their uplift behaviour when they are laid as single as well as in a group of two symmetrical anchors. A large-scale model testing facility has been developed and fabricated in order to perform the physical modelling. In physical modelling, poorly graded, dry Quartzanium sand is utilized as the foundation material. PLAXIS3D, a finite-element software for geotechnical engineering, has been used to validate the experimental results obtained from the large-scale model testing facility. The effects of embedment depth and size of the anchor plate as well as layering in soil media are the parameters considered in order to determine the interaction factors with respect to the uplift capacity and displacement of anchors.

SALIVARY DIAGNOSTICS AND ITS IMPLEMENTATION IN DIAGNOSIS OF COVID19

The conventional treatment for vertical maxillary excess due to Skeletal class II base, is surgical reduction and rigid fixation which has decreased patient acceptance. However, intrusion of some selected MVE cases can be achieved with minimal intervention using mini plate anchorage, thus expediting and simplifying their management. A 15 year old female patient came with a complaint of forwardly placed teeth in the upper front tooth region of the jaw. Intraoral examination showed class II molar occlusion on both sides with increased overjet and overbite. The cephalometric analysis showed class II skeletal relationship with vertical maxillary excess. The treatment plan included Fixed appliance with extraction of 14,24,35, then miniplates and miniimplant assisted anterior maxillary retraction and intrusion. At the end of the treatment anterior maxillary retraction and intrusion was achieved. Thus the hypothesis was accepted as retraction and intrusion using mini plates is an easy, efficient, safe and cost- effective option in the management of VME. It is less invasive with acceptable clinical and radiographic outcome, while avoiding surgery under GA with its risk and complication. Careful case selection is needed for achieving satisfactory result and smile.

Towards a simple and reliable method for calculating uplift capacity of plate anchors in sand

This paper investigates the uplift capacity of horizontal plate anchors in sand through finite element analyses and centrifuge experiments. The finite element simulations adopt a sophisticated bounding surface plasticity model that accounts for stress- and density-dependent behaviour, as well as loading- and fabric-related anisotropic effects in sands. Failure mechanisms at peak anchor capacity show that failure occurs progressively, with a marked decrease in mobilised friction angle within the shear bands close to the anchor edge. Numerical simulations of a large set of centrifuge experiments on rectangular, strip, and circular plates at different relative densities and stress levels are in good agreement for dense conditions, but perform more poorly for loose conditions due mainly to the open cone yield surface in the bounding surface model. Equivalent comparisons with current limit equilibrium methods highlight the challenges in direct application of element-level strength equations. Finally, the paper proposes a modified limit equilibrium solution based on a “rigid-block” failure mechanism extending to the soil surface, but with anchor factors that encompass the results from the finite element simulations. The modified solution provides a higher level of agreement with results from a large database of plate and pipeline test data than existing limit equilibrium methods.

Seismic performance of steel frame with a self-centering beam

Self-centering moment-resisting frames are capable of returning to their original plumb position after a severe earthquake, having sustained no or only slight structural damage. In this paper, a steel frame composed of a self-centering I-beam is proposed, with its capacities for self-centering and inelastic deformation provided by post-tensioned (PT) strands and energy dissipating (ED) elements, respectively. Based on an analysis of its mechanical properties, an experiment involving this self-centering frame under cyclic loading was conducted to investigate its load transfer mechanism, bearing capacity, hysteretic behaviour, ductility, energy dissipating capacity and self-centering capacity. The results agree well with the theoretical analysis, and it can be concluded that its force-displacement hysteretic curve has a typical flag shape. The plastic deformation of the specimen is concentrated on the ED elements, which can be replaced easily after an earthquake. As the gap-opening of the anchorage plate occurs, the PT strands and ED elements provide the bending stiffness for the structure. When the story drift is loaded to 4%, the skeleton curve does not have a descending section, which means that the structure still has sufficient bearing and deformation capacities. The analysis of the residual story drift and the equivalent viscous damping coefficient shows that the frame has good energy dissipating and self-centering capabilities. A finite element model is established with OpenSees to simulate the seismic behaviour of the self-centering frame. Using the model, the seismic performance of the frame is analysed in terms of its structural parameters, including the section area of the PT strands, initial stress on the PT strands and section area of the ED elements.

Study on the Uplift Resistance of a Joint Board Cable Foundation Considering the Critical Burial Depth

Joint board cable foundation is a kind of foundation form proposed by the author which is applied to transmission lines. In the study of pullout resistance of a joint board cable foundation, the most important factor is the critical depth of the anchor plate. Theoretical analyses, numerical simulations, and field tests were carried out to study the impact of the critical burial depth on the uplift capacity. Test results were corrected by the back-stepping cohesive force method. The theoretical analyses, numerical simulations, and field test results are consistent. It is found that the development of the plastic failure zone in the foundation is directly controlled by the shear strain. Through the field test, the pullout resistance of the anchor plate is studied, and it is found that the depth ratio has the most influence on the pullout capacity of the anchor plate. The field tests also provide valuable data for theoretical calculation, numerical simulation, and design of joint board cable foundations. The field test data analysis and numerical simulation results show that the optimal burial depth ratio of the joint board cable foundation is about 2.5–3.0. Therefore, in the design of the joint board cable foundation, 2.5 can be adopted as the critical depth ratio of the joint board cable.

New insights into the failure mechanisms of horizontal plate anchors in clay during pull-out

Offshore wind developments are moving towards deep-water regions where energy is abundant, visual impact is minimised and the larger turbine sizes can make the energy production more cost-effective. One of the key challenges facing the industry is the development of reliable substructures. While fixed foundation systems are widely used for shallow-water (<60 m) developments, permanent anchors are seen as one of the most viable mooring solutions for floating structures in deep water. In the current study, the pull-out behaviour of square plate anchors in clay was investigated using large-displacement finite-element analysis. The anchor capacity and failure mechanism were considered for a range of embedment ratios and undrained shear strengths. Three distinct modes of anchor failure identified in previous studies were examined through the analysis of four descriptors including: the pull-out capacity of the anchor, the pull-out displacement required to mobilise this capacity, the energy absorbed by the anchor during pull-out and the variation of the pull-out capacity with respect to a normalised overburden pressure. The findings of the study are presented in the form of a series of charts that can aid design through understanding of the factors controlling the development of anchor failure modes, in addition to identifying the transition point between different failure mechanisms.

Failure and Deformation Mechanisms of Vertical Plate Anchors Subjected to Lateral Loading in Sand

Abstract This paper presents an experimental study on the pullout behavior of a vertical plate anchor buried in sand under lateral loading, using the digital image correlation (DIC) technique. Base...

Seismic stability of obliquely loaded circular plate anchors

The vertical uplift resistance of obliquely loaded circular plate anchors buried in sand subjected to seismic loadings has been obtained in this paper. The pseudo-dynamic approach based on kinematic theorem of limit analysis has been applied for performing the analysis in which the nonlinear acceleration distributions are incorporated considering standing shear (S) and primary (P) wave propagations within the soil medium. Results are obtained in terms of seismic uplift factor (Fγs) due to soil self-weight component for a wide range of parameters. Through a parametric study, the effects of different parameters including normalized frequencies of Shear (S) and Primary (P) waves and damping ratio (ξ) of soil are highlighted. On account of amplified accelerations effects, the value of Fγs has been found to drastically reduce with an increase in load inclination (θ), horizontal and vertical seismic acceleration coefficients (kh and kv). The results show that the influence of damping ratio (ξ) of soil becomes more dominant particularly for frequencies close to the fundamental frequency of P wave.