Numerical Investigation Into the Keying Process of a Plate Anchor Vertically Installed in Cohesionless Soil

2018 ◽  
Author(s):  
Nabil Al Hakeem ◽  
Charles Aubeny
Keyword(s):  
Peak Load ◽  
Offshore Structures ◽  
Cohesionless Soil ◽  
Soil Conditions ◽  
Embedment Depth ◽  
Pullout Capacity ◽  
Vertical Loading ◽  
Wide Range ◽  
Plate Anchor ◽  
Plate Anchors

Vertically driven plate anchors offer an attractive anchoring solution for floating offshore structures, as they are both highly efficient and suitable for a wide range of soil conditions. Since they are oriented vertically after installation, keying is required to orient the anchor into the direction of applied loading. Simulation of the keying process has not been extensively investigated by previous research, especially for cohesionless soil. Reliable prediction of irrecoverable embedment loss during keying is needed, since such loss can lead to significant reduction in the uplift capacity of the plate anchors. Large deformation finite element analyses LDFE method using RITSS (Remeshing and Interpolation Technique with Small Strain) were used to simulate the keying process of strip plate anchor embedded in uniform cohesionless soil. LDFE showed that the loss in embedment depth of plate anchor during rotation is inversely proportional to the loading eccentricity e/B. It was also found that the maximum pullout capacity occurs before the end of keying process at orientations between 60° to 85° degrees for vertical loading. Also, the LDFE study showed that reduced elastic soil stiffness leading to increased levels of displacement at which the peak load is approached.

scholarly journals Ultimate Pullout Capacity of a Square Plate Anchor in Clay with an Interbedded Stiff Layer

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tugen Feng ◽  
Jingyao Zong ◽  
Wei Jiang ◽  
Jian Zhang ◽  
Jian Song
Keyword(s):  
Finite Element ◽  
Empirical Formula ◽  
Soil Layer ◽  
Embedment Depth ◽  
Layered Soils ◽  
Pullout Capacity ◽  
Plate Anchor ◽  
Square Plate ◽  
Plate Anchors ◽  
Ultimate Pullout Capacity

Three-dimensional nonlinear numerical analysis is carried out to determine the ultimate pullout capacity of a square plate anchor in layered clay using the large finite element analysis software ABAQUS. An empirical formula for the pullout bearing capacity coefficient of a plate anchor in layered soils is proposed based on the bearing characteristics of plate anchors in single-layer soils. The results show that a circular flow (circulation field) is induced around the plate anchor during the uplift process and that the flow velocity and circulation field range are mainly affected by the properties of the soil around the plate anchor. The bearing characteristics of plate anchors in layered soils are influenced by factors such as the embedment depth of the plate anchor, the friction coefficient between the soil and the plate anchor, the thickness of the upper soil layer, and the thickness of the middle soil layer. The rationality of the finite element numerical calculation results and the empirical formula is verified by comparing the results from this study with results previously reported in the literature.

scholarly journals Macro-element modelling of suction-embedded plate anchors for floating offshore structures

2019 ◽  
Vol 92 ◽  
pp. 16009
Author(s):  
Anderson Peccin Da Silva ◽  
Andrea Diambra ◽  
Dimitris Karamitros
Keyword(s):  
Good Accuracy ◽  
Large Range ◽  
Element Model ◽  
Offshore Structures ◽  
Hardening Rule ◽  
Centrifuge Tests ◽  
Wide Range ◽  
Plastic Potential ◽  
Macro Element ◽  
Plate Anchors

This work presents a new macro-element model to predict the behaviour of Suction Embedded Plate Anchors (SEPLAs) for floating offshore structures during keying and loading stages. Differently from previously published models for anchors, this new model is characterised by (i) a non-associated plastic potential with the aim of improving the prediction of anchor trajectory for the whole displacement domain and for a large range of padeye offsets; and (ii) by a strain-hardening rule enabling to predict the force and displacement mobilisation from the early stages of the keying process. The model was calibrated against LDFE analyses and compared with a broad set of LDFE and centrifuge tests results. The model proves capable of reproducing anchor rotation and displacement with good accuracy for a wide range of padeye offsets and distinct studies from the literature.

NORMALLY LOADED INCLINED STRIP ANCHORS IN COHESIONLESS SOIL

2020 ◽  
Author(s):  
Nabil Al Hakeem ◽  
Charles Aubeny
Keyword(s):  
Finite Element ◽  
Scale Effects ◽  
Orientation Angle ◽  
Cohesionless Soil ◽  
Limited Attention ◽  
Embedment Depth ◽  
Finite Element Analyses ◽  
Dense Sand ◽  
Full Characterization ◽  
Plate Anchors

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 0o to 90o 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 degrees 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.

Design load of rigid footings on sand

2010 ◽  
Vol 47 (8) ◽  
pp. 872-884 ◽  
Author(s):  
Edgar G. Diaz ◽  
Fernando Rodríguez-Roa
Keyword(s):  
Standard Penetration Test ◽  
Design Criterion ◽  
Cohesionless Soil ◽  
Unit Weight ◽  
Embedment Depth ◽  
Penetration Test ◽  
Soil Pressure ◽  
In Situ Tests ◽  
Vertical Loading ◽  
Design Load

Experimental evidence has shown that most current methods are not able to predict design loads of footings on cohesionless soil with an acceptable degree of accuracy. In the present study, a simple and realistic settlement-based method is proposed to estimate the design load of rigid footings on sand subjected to static vertical loading. The design criterion based on restricting the end-of-construction settlement to 16 mm because of the inherent variability of the real soil deposits is herein adopted. A series of finite-element analyses based on an advanced constitutive model were carried out to study the load–settlement response of footings supported on 14 sandy soils. Routine design charts were developed to predict the net allowable soil pressure of footings on normally consolidated and overconsolidated sands. These charts consider footing shape, embedment depth, grain diameters D10 and D60, particle shape, unit weight (or submerged unit weight for saturated sands), and indirect measurements of the shear strength derived from in situ tests, such as relative density, standard penetration test (SPT) or cone penetration test (CPT). As shown, the proposed charts match well with available experimental data.

scholarly journals Design and analysis of plate anchors in sand

2021 ◽  
Author(s):  
Muhammad Waseem
Keyword(s):  
Failure Modes ◽  
Design Procedure ◽  
Embedment Depth ◽  
Offshore Platforms ◽  
Failure Plane ◽  
Transmission Towers ◽  
Plate Anchor ◽  
Plate Anchors ◽  
Anchor Design ◽  
Uplift Forces

Plate anchors, as an efficient and reliable anchorage system, have been widely used to resist uplift forces produced by structures, such as transmission towers, offshore platforms, submerged pipelines, and tunnels. In order to design a plate anchor it is important to know the factors which influence the design and uplift behavior of anchors embedded in sand. In this report a number of model uplift tests and numerical investigations made by different authors are described and based on these readings the uplift behavior of anchors in sand is explored and anchor's design procedure is described. In addition, basic anchor types, failure modes in anchors, and design codes are mentioned. Based on this study, it is found that the failure plane and uplift capacity is significantly influenced by the soil density and embedment depth. Therefore, it is concluded that the influence of sand density and embedment depth should be considered in anchor design.

scholarly journals Design and analysis of plate anchors in sand

2021 ◽  
Author(s):  
Muhammad Waseem
Keyword(s):  
Failure Modes ◽  
Design Procedure ◽  
Embedment Depth ◽  
Offshore Platforms ◽  
Failure Plane ◽  
Transmission Towers ◽  
Plate Anchor ◽  
Plate Anchors ◽  
Anchor Design ◽  
Uplift Forces

Plate anchors, as an efficient and reliable anchorage system, have been widely used to resist uplift forces produced by structures, such as transmission towers, offshore platforms, submerged pipelines, and tunnels. In order to design a plate anchor it is important to know the factors which influence the design and uplift behavior of anchors embedded in sand. In this report a number of model uplift tests and numerical investigations made by different authors are described and based on these readings the uplift behavior of anchors in sand is explored and anchor's design procedure is described. In addition, basic anchor types, failure modes in anchors, and design codes are mentioned. Based on this study, it is found that the failure plane and uplift capacity is significantly influenced by the soil density and embedment depth. Therefore, it is concluded that the influence of sand density and embedment depth should be considered in anchor design.

Experimental Study on the Strain Softening Behavior of Plate Anchors in Clay Under Cyclic Loading

2014 ◽  
Author(s):  
Long Yu ◽  
Qi Zhou ◽  
Jun Liu
Keyword(s):  
Cyclic Loading ◽  
Bearing Capacity ◽  
Stress Level ◽  
Strain Softening ◽  
High Stress ◽  
Offshore Structures ◽  
Pullout Capacity ◽  
Softening Behavior ◽  
Plate Anchors ◽  
High Stress Level

Many geotechnical designs require knowledge of soil uplift resistance where the foundation must withstand tensile forces, such as wind loading on transmission towers, wave action on offshore structures, and buoyancy forces on buried pipelines. Most existing researches on the bearing capacity of plate anchors are limited to static analyses. The effects of offshore cyclic loading on the bearing capacity of plate anchors are not very clear. The ultimate pullout capacity of plate anchors in clay may decrease as the accumulated plastic shear strain grows due to the strain-softening of clay under cyclic loading. In this study, 1 g model tests were carried out to estimate the softening behavior of plate anchors including one low stress level case and two high stress level cases. PIV (Particle Image Velocimetry) technique was used to investigate the soil flow mechanism of the anchor at low stress level. Numerical analyses are carried out to simulate the large deformation behavior of the anchor at high stress level under cyclic loading.

Deformation Mechanism of Plate Anchor in Sand

2011 ◽  
Vol 250-253 ◽  
pp. 1469-1473
Author(s):  
Xin Zhang ◽  
Jin Chao Yue
Keyword(s):  
Cross Correlation ◽  
Failure Modes ◽  
Cohesionless Soil ◽  
Loading Capacity ◽  
Reliable Prediction ◽  
Dense Sand ◽  
Model Study ◽  
Plate Anchor ◽  
Uplift Resistance ◽  
Plate Anchors

Plate anchor is one of the most popular types of anchors widely used in geotechnical engineering. Reliable prediction of the ultimate uplift resistance of plate anchors requires its failure modes well understood. In this paper, an image-based deformation technique, the digital image cross-correlation (DIC), is used to measure the sand deformations around a scaled semi-circular anchor during uplifting. A series of tests have been conducted to investigate the failure modes of plate anchors in both loose and dense sand. Two distinctively different failure modes are measured by using DIC in both loose and dense sand respectively. This model study improves the understanding of the failure and development of loading capacity of uplift anchor in cohesionless soil.

Numerical study of pull-out capacities of dynamically embedded plate anchors

2014 ◽  
Vol 51 (11) ◽  
pp. 1263-1272 ◽  
Author(s):  
D. Wang ◽  
C.D. O’Loughlin
Keyword(s):  
Numerical Study ◽  
Plate Thickness ◽  
Capacity Factor ◽  
Unit Weight ◽  
Embedment Depth ◽  
Rectangular Plates ◽  
Overburden Pressure ◽  
Vertical Loading ◽  
Pull Out ◽  
Plate Anchors

Dynamically embedded plate anchors (DEPLAs) are a type of offshore anchor that combine the capacity advantages of vertically loaded plate anchors with the installation benefits of dynamically installed anchors. DEPLA capacity under monotonic loading conditions in clay has been investigated through centrifuge and field tests. In this paper, the monotonic capacity of DEPLAs in normally consolidated clay was studied using a three-dimensional large deformation finite element approach based on frequent mesh regeneration. Results from the numerical simulations were validated by comparison with centrifuge test data and existing numerical and analytical solutions for circular and rectangular plates. The effect of anchor embedment depth, anchor roughness, fluke (or plate) thickness, plate inclination, and DEPLA geometry were investigated in a parametric study where soil was prescribed to remain attached to the DEPLA base. The findings indicate that for a horizontal anchor subjected to vertical loading, most DEPLA geometries exhibit deep behaviour at an embedment ratio of 2.5, but that this embedment ratio is dependent upon the plate inclination, with vertical plates requiring the highest embedment depth for a deep localized failure mechanism. At a shallow embedment depth equal to one plate diameter, the reduction in capacity factor as the plate inclination changes from horizontal to vertical is 23.4%, compared with 1.3% at an embedment depth equal to four plate diameters. Plate roughness and fluke thickness are shown to have a minimal effect on the anchor capacity factor for vertical loading. Analyses that considered the breakaway (no tension) at the DEPLA base demonstrated that the anchor capacity factor approaches the no breakaway value as the embedment depth increases and as the soil strength (relative to the effective unit weight of the soil) decreases. The paper proposes a simple means of approximating the anchor capacity factor for breakaway conditions, by summing the capacity factor in weightless soil (which is unique for a given DEPLA geometry) and the normalized overburden pressure.

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