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failure envelopes of Single-Plate Rigid Helical Anchors for Floating Offshore Wind Turbine

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China Ocean Engineering 2023年第6期37卷 1000-1010页

作者： CHEN Hong-zhen WANG Le TIAN Ying-hui ZHANG Chun-hui SHEN Zhi-chao LIU Meng-meng State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300072China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Department of Infrastructure Engineering Faculty of Engineering and Information Technology The University of MelbourneVictoria 3010Australia School of Civil Engineering Hebei University of Science and TechnologyShijiazhuang 050018China Hebei Technological Innovation Center of Disaster Prevention and Mitigation Engineering of Geotechnical and Structural System Shijiazhuang 050018China School of Marine Science and Engineering South China University of TechnologyGuangzhou 511442China Institute of Ocean Energy and Intelligent Construction Tianjin University of TechnologyTianjin 300384China

Helical anchor is a kind of novel foundation for floating offshore wind turbines,which should be subjected to combined tensile loading caused by wind,wave and ***,the research about the capacity of helical anchor was mainly examined under uniaxial loading and scarcely explored under combined *** this study,three-dimensional finite element limit analysis is adopted to assess the bearing capacities of single-plate rigid helical anchors with different ratios of helix to shaft diameter,D_(H)/D_(S) and embedment ratios L/D_(S).Result shows that the vertical,horizontal and moment bearing capacities increase with increasing D_(H)/D_(S) and L/D_(S).The normalized V-H failure envelopes expands with increasing L/D_(S),while the normalized V-M failure envelopes tend to contract with the increase of D_(H)/D_(S).With increasing D_(H)/D_(S) or decreasing L/D_(S),the normalized H-M failure envelopes expand when the horizontal and moment loading act in the same direction and contract when they act in the opposite *** effect of D_(H)/D_(S) and L/D_(S) on the shape of H-M failure envelope become insignificant when L/D_(S)≥4.A series of failure mechanisms under different loading conditions were observed and can be used to explain the ***,a series of approximate expressions were proposed to fit the uniaxial bearing capacities and the failure envelopes.

关键词： helical anchors bearing capacity failure envelope clay

A temperature/strain-rate-dependent finite deformation constitutive and failure model for solid propellants

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中国科学:物理学、力学、天文学英文版 2023年第9期66卷 63-78页

作者： Ming Lei Erhao Chen Zeang Zhao Lihua Wen Jinyou Xiao Xiao Hou School of Astronautics Northwestern Polytechnical UniversityXi’an 710072China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing 100081China China Aerospace Science and Technology Corporation Beijing 100048China

The stress-strain response under progressive damage and the ultimate failure of solid propellants are two key issues affecting the integrity of solid rocket *** research primarily focused on the progressive damage in solid propellants during production and ***,they failed to take the temperature/strain-rate-dependent ultimate failures into *** failure strains of solid propellants are experimentally observed to show strong temperature/strain-rate dependence and exhibit an abnormal evolution at low and high temperatures,*** increasing loading strain rate,the failure strains decrease at low temperatures near the glass transition temperature(T_g)but increase at high temperatures far above T_(g).In this study,we introduce the glassy and rubbery failure criteria based on strain energy densities at ultralow and ultrahigh temperatures,respectively,into a viscoelastic constitutive model and build a unified model for the progressive damage and the ultimate failure of solid *** the introduction of these two additional criterion parameters,the developed model can effectively predict the yield-type stress-strain responses,microscopic damage-induced volume dilatations,and temperature/strain-ratedependent ultimate failures of the solid propellants by comparing the model predictions with the experimental *** competition between the glassy failure and the rubbery failure results in the propellants exhibiting a maximum break strain near the glass transition ***,when the strain rate is increased,the propellants exhibit a predominantly glassy response,which shifts the failure envelope toward a higher *** induces an abnormal evolution of failure strains by making the propellants stretchable at high temperatures and brittle at low temperatures.

关键词： viscoelastic material polymeric material constitutive behavior fracture toughness failure envelope

Study on failure Mechanism and Bearing Capacity of Three-Dimensional Rectangular Footing Subjected to Combined Loading

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China Ocean Engineering 2008年第2期22卷 313-330页

作者：张其一栾茂田王忠涛 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

This paper presents two kinematic failure mechanisms of threc-dimensional rectangular footing resting on homogeneous undrained clay foundation under uniaxial vertical loading and uniaxial moment loading. The failure mechanism under vertical loading comprises a plane strain Prandti-type mechanism over the central part of the longer side, and the size of the mechanism gradually reduces at the ends of the longer side and over the shorter side as the corner of rectangular footing is being approached where the direction of soil motion remains normal to each corresponding side respectively. The failure mechanism under moment loading comprises a plane strain scoop sliding mechanism over the central part of the longer side, and the radius of scoop sliding mechanism increases linearly at the ends of the longer side. On the basis of the kinematic failure mechanisms mentioned above, the vertical ultimate bearing capacity and the ultimate bearing capacity against moment or moment ultimate bearing capacity are obtained by use of upper bound limit analysis theory. At the same time, numerical analysis results, Skempton＇ s results and Salgado et al. ＇s results are compared with this upper bound solution. It shows that the presented failure mechanisms and plastic limit analysis predictions are validated. In order to investigate the behaviors of undrained clay foundation beneath the rectangular footing subjected to the combined loadings, numerical analysis is adopted by virtue of the general-purpose FEM software ABAQUS, where the clay is assumed to obey the Mohr-Coulomb yielding criterion. The failure envelope and the ultimate bearing capacity are achieved by the numerical analysis results with the varying aspect ratios from length L to breadth B of the rectangular footing. The failure mechanisms of rectangular footing which are subjected to the combined vertical loading V and horizontal loading H （Vertical loading V and moment loading M, and horizontal loading H and moment loading M

关键词： rectangular footing upper bound limit analysis failure mechardsm failure envelope combined loading

A simplified three-dimensional extension of Hoek-Brown strength criterion

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第3期13卷 568-578页

作者： Hangzhou Li Tong Guo Yalin Nan Bo Han Department of Civil Engineering Xi’an Jiaotong UniversityXi’anShaanxi710049China Shaanxi Engineering Research Center of Soil Body China Electronic Research Institute of Engineering Investigation and DesignXi’anShaanxi710054China

The Hoek-Brown(HB)strength criterion has been applied widely in a large number of projects around the ***,this criterion ignores the intermediate principal stress *** evidences have demonstrated that the rock strength is dependent on *** it is necessary to extend the HB criterion into a three-dimensional(3D)*** this study,the effect of s2 on the strength of rocks is identified by reviewing the true triaxial tests of various rock types reported in the literature.A simple 3D strength criterion is *** modified criterion is verified by the true triaxial tests of 13 rock *** results indicate that the modified criterion can achieve a good fit to most of rock *** can represent a series of criteria as b *** comparisons,several existing 3D versions of the HB criterion are selected to predict the strengths of these rock *** is indicated that the proposed criterion works better than other criteria.A substantial relationship between parameter b and the unconfined compressive strength is established,which guarantees that the proposed criterion can still work well even in the absence of true triaxial test data.

关键词： Hoek-Brown(HB)strength criterion Three-dimensional(3D)strength criterion Intermediate principal stress failure envelope

Experimental study on biaxial mechanical behavior of concrete suffered high temperature and constitutive model

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Journal of Harbin Institute of Technology(New Series) 2008年第5期15卷 679-685页

作者：张众宋玉普覃丽坤 School of Architecture Engineering Shandong University of Technology State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology School of Architecture and Civil Engineering Dalian Nationalities University

Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.

关键词： high temperature biaxial compression initial elastic modulus failure envelope constitutive model