Capacities of tripod bucket foundation under uniaxial and combined loading considering adhesion factor

The composite bucket foundation of offshore wind turbines is subjected to a variety of loads in the marine environment, such as horizontal load H, vertical load V , bending moment M, and torque T. In addition, due to the characteristics of its connection section, the water flow around the foundation will produce scour pits of various degrees, reducing the depth of the bucket foundation, which has a nonnegligible impact on the overall stability of the bucket foundation. In this paper, the failure envelope characteristics of different combinations of loads on bucket foundations, including V -H-T, V -M-T, conventional V -H-M, and noncoplanar V -H-M, are numerically investigated with considering different scour depths. The numerical results indicate that the V -H-T, V -M-T, conventional V -H-M, and noncongruent V -H-M failure envelopes gradually shrink inwards with increasing scour depth, and the stability of the composite bucket foundation decreases; the conventional V -H-M failure envelope shows an asymmetry of convexity to the right, and the noncongruent V -H-M failure envelope shows an asymmetry of outward convexity to the left and right. The corresponding mathematical expressions for the failure envelope are obtained through the normalized fitting process, which can be used to evaluate the stability of the bucket foundation based on the relative relationship between the failure envelope and the actual load conditions, which can provide practical guidance for engineering design.

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The capacities of tripod bucket foundation under uniaxial and combined loading

Ocean Engineering ◽

10.1016/j.oceaneng.2020.108400 ◽

2020 ◽

pp. 108400

Author(s):

Ben He ◽

Jun Jiang ◽

Jian Cheng ◽

Jingbin Zheng ◽

Dong Wang

Keyword(s):

Combined Loading ◽

Bucket Foundation

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Evaluation of Undrained Bearing Capacities of Wide-Shallow Bucket Foundation with Honeycomb Bulkheads in Clay

Advances in Civil Engineering ◽

10.1155/2019/9769042 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Qingshan Wang ◽

Xun Han ◽

Yunfei Guan ◽

Yongyong Cao ◽

Wenxuan Li

Keyword(s):

Shear Strength ◽

Three Dimensional ◽

Offshore Wind ◽

Combined Loading ◽

Vertical Load ◽

Bucket Foundation ◽

Failure Envelopes ◽

Soil Shear Strength ◽

New Type ◽

The Moment

As a new type of offshore wind foundation, the wide-shallow bucket foundation with honeycomb bulkheads mainly bears vertical, horizontal, and moment loads. As yet, no systematic study has been conducted regarding the effects of honeycomb bulkheads on the undrained bearing capacities of the wide-shallow bucket foundation. In this study, a large number of three-dimensional (3D) finite element (FE) analyses were performed to investigate the undrained bearing capacities of the wide-shallow bucket foundations with and without honeycomb bulkheads, thereby evaluating the influence of honeycomb bulkheads on the bearing capacities under different conditions. The results show that under uniaxial loading, the uniaxial bearing capacities of the wide-shallow bucket foundation are basically unaffected by the honeycomb bulkheads in homogeneous clay. For nonhomogeneous clay, the moment bearing capacity will be considerably enhanced with the increase in soil shear strength heterogeneity. Under combined loading, the honeycomb bulkheads will enhance the combined bearing capacities only in nonhomogeneous clay. The enhancement effects will increase with the increase in soil shear strength heterogeneity but decrease with the increase in vertical load. Besides, the simplified equations for calculating the uniaxial bearing capacities of the wide-shallow bucket foundation with honeycomb bulkheads are also proposed considering the influence of embedment ratio and soil shear strength heterogeneity. At last, the parameters of an approximating expression are fitted to predict the failure envelopes of this foundation under combined loading.

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The Numerical Simulation of Bearing Capacity of Pile-Bucket Foundation under Combined Loading of Up-Pull and Horizontal Force

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.2171 ◽

2011 ◽

Vol 243-249 ◽

pp. 2171-2175

Author(s):

Wen Bai Liu ◽

Long Zhao ◽

Ning Jia

Keyword(s):

Numerical Simulation ◽

Bearing Capacity ◽

Horizontal Displacement ◽

Calculation Model ◽

Combined Loading ◽

Horizontal Load ◽

Horizontal Force ◽

Bucket Foundation ◽

Load Increase ◽

Pulling Force

By using ABAQUS software to conduct numerical simulation and model test of pile-bucket under mono-loading of up-pulling force and horizontal force, then make comparison of both results to testify the accuracy of finite calculation model. Then by numerical simulation to study bearing capacity of pile-bucket foundation under combined loading of up-pull and horizontal force. The result shows the pile-bucket foundation horizontal displacement will increase with the increase of up-pulling force at the limit horizontal load, and the horizontal displacement becomes more obvious as the up-pulling load increasing if providing greater horizontal loading force. Before the up-pulling force reaches the limit, horizontal load will not affect up-pulling displacement; after the up-pulling force reaches the limit, the horizontal load can slightly reduce the up-pulling displacement of pile top. The effect of up-pulling load increase on horizontal displacement is obvious for pile depth in soil at 0~15m, but very tiny for pile body with buried depth over 15m.

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Faculty Opinions recommendation of Outer membrane adhesion factor multivalent adhesion molecule 7 initiates host cell binding during infection by gram-negative pathogens.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.12729957.13996055 ◽

2011 ◽

Author(s):

Rino Rappuoli ◽

Davide Serruto

Keyword(s):

Host Cell ◽

Outer Membrane ◽

Adhesion Molecule ◽

Cell Binding ◽

Gram Negative ◽

Membrane Adhesion ◽

Adhesion Factor

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The Influence of Loads Superposition, Deterioration Due to Cracks and Residual Stresses on the Strength of Tubular Junction

Revista de Chimie ◽

10.37358/rc.17.6.5655 ◽

2017 ◽

Vol 68 (6) ◽

pp. 1267-1273

Author(s):

Valeriu V. Jinescu ◽

Angela Chelu ◽

Gheorghe Zecheru ◽

Alexandru Pupazescu ◽

Teodor Sima ◽

...

Keyword(s):

Stress Concentration ◽

Residual Stresses ◽

Bending Moment ◽

Combined Loading ◽

Torsional Moment ◽

Calculation Methods ◽

State Of Stress ◽

Cracked Structures ◽

Total Participation ◽

Theoretical Results

In the paper the interaction of several loads like pressure, axial force, bending moment and torsional moment are analyzed, taking into account the deterioration due to cracks and the influence of residual stresses. A nonlinear, power law, of structure material is considered. General relationships for total participation of specific energies introduced in the structure by the loads, as well as for the critical participation have been proposed. On these bases: - a new strength calculation methods was developed; � strength of tubular cracked structures and of cracked tubular junction subjected to combined loading and strength were analyzed. Relationships for critical state have been proposed, based on dimensionless variables. These theoretical results fit with experimental date reported in literature. On the other side stress concentration coefficients were defined. Our one experiments onto a model of a pipe with two opposite nozzles have been achieved. Near one of the nozzles is a crack on the run pipe. Trough the experiments the state of stress have been obtained near the tubular junction, near the tip of the crack and far from the stress concentration points. On this basis the stress concentration coefficients were calculated.

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Buckling of Circular Cylindrical Shells Using a Displacement Function

Journal of Engineering for Industry ◽

10.1115/1.3438513 ◽

1974 ◽

Vol 96 (4) ◽

pp. 1322-1327

Author(s):

Shun Cheng ◽

C. K. Chang

Keyword(s):

Boundary Conditions ◽

Axial Compression ◽

Cylindrical Shells ◽

External Pressure ◽

Displacement Function ◽

Combined Loading ◽

Trial Solution ◽

Governing Differential Equation ◽

Circular Cylindrical Shells ◽

The Stability

The buckling problem of circular cylindrical shells under axial compression, external pressure, and torsion is investigated using a displacement function φ. A governing differential equation for the stability of thin cylindrical shells under combined loading of axial compression, external pressure, and torsion is derived. A method for the solutions of this equation is also presented. The advantage in using the present equation over the customary three differential equations for displacements is that only one trial solution is needed in solving the buckling problems as shown in the paper. Four possible combinations of boundary conditions for a simply supported edge are treated. The case of a cylinder under axial compression is carried out in detail. For two types of simple supported boundary conditions, SS1 and SS2, the minimum critical axial buckling stress is found to be 43.5 percent of the well-known classical value Eh/R3(1−ν2) against the 50 percent of the classical value presently known.

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Design of Pipeline Composite Repairs: From Lab Scale Tests to FEA and Full Scale Testing

Volume 2: Pipeline Integrity Management ◽

10.1115/ipc2014-33201 ◽

2014 ◽

Author(s):

Remy Her ◽

Jacques Renard ◽

Vincent Gaffard ◽

Yves Favry ◽

Paul Wiet

Keyword(s):

Finite Element ◽

Full Scale ◽

Combined Loading ◽

Material Strength ◽

Repair System ◽

Loading Conditions ◽

Original Design ◽

Composite Repair ◽

Repair Systems ◽

Composite Properties

Composite repair systems are used for many years to restore locally the pipe strength where it has been affected by damage such as wall thickness reduction due to corrosion, dent, lamination or cracks. Composite repair systems are commonly qualified, designed and installed according to ASME PCC2 code or ISO 24817 standard requirements. In both of these codes, the Maximum Allowable Working Pressure (MAWP) of the damaged section must be determined to design the composite repair. To do so, codes such as ASME B31G for example for corrosion, are used. The composite repair systems is designed to “bridge the gap” between the MAWP of the damaged pipe and the original design pressure. The main weakness of available approaches is their applicability to combined loading conditions and various types of defects. The objective of this work is to set-up a “universal” methodology to design the composite repair by finite element calculations with directly taking into consideration the loading conditions and the influence of the defect on pipe strength (whatever its geometry and type). First a program of mechanical tests is defined to allow determining all the composite properties necessary to run the finite elements calculations. It consists in compression and tensile tests in various directions to account for the composite anisotropy and of Arcan tests to determine steel to composite interface behaviors in tension and shear. In parallel, a full scale burst test is performed on a repaired pipe section where a local wall thinning is previously machined. For this test, the composite repair was designed according to ISO 24817. Then, a finite element model integrating damaged pipe and composite repair system is built. It allowed simulating the test, comparing the results with experiments and validating damage models implemented to capture the various possible types of failures. In addition, sensitivity analysis considering composite properties variations evidenced by experiments are run. The composite behavior considered in this study is not time dependent. No degradation of the composite material strength due to ageing is taking into account. The roadmap for the next steps of this work is to clearly identify the ageing mechanisms, to perform tests in relevant conditions and to introduce ageing effects in the design process (and in particular in the composite constitutive laws).

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