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Assessment of cyclic deformation and critical stress amplitude of jointed rocks via cyclic triaxial testing

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第6期15卷 1370-1390页

作者： Waranga Habaraduwa Peellage Behzad Fatahi Haleh Rasekh School of Civil and Environmental Engineering University of Technology SydneySydneyAustralia

Jointed rock specimens with a natural replicated joint surface oriented at a mean dip angle of 60were prepared,and a series of cyclic triaxial tests was performed at different confining pressures and cyclic deviatoric stress amplitudes.The samples were subjected to 10,000 loading-unloading cycles with a frequency of 8 Hz.At each level of confining pressure,the applied cyclic deviatoric stress amplitude was increased incrementally until excessive deformation of the jointed rock specimen was observed.Analysis of the test results indicated that there existed a critical cyclic deviatoric stress amplitude(i.***.critical dynamic deviatoric stress)beyond which the jointed rock specimens yielded.The measured critical dynamic deviatoric stress was less than the corresponding static deviatoric stress.At cyclic deviatoric stress amplitudes less than the critical dynamic deviatoric stress,minor cumulative residual axial strains were observed,resulting in hysteretic damping.However,for cyclic deviatoric stresses beyond the critical dynamic deviatoric stress,the plastic strains increased promptly,and the resilient moduli degraded rapidly during the initial loading cycles.Cyclic triaxial test results showed that at higher confining pressures,the ultimate residual axial strain attained by the jointed rock specimen decreased,the steadystate dissipated energy density and steady-state damping ratio per load cycle decreased,while steadystate resilient moduli increased.

关键词： Cyclic triaxial test Jointed rock Joint surface Confining pressure Cyclic deviatoric stress amplitude Failure residual deformation Dissipated energy

Inelastic deformation Analysis of Aluminum Bending Members

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Tsinghua Science and Technology 2006年第6期11卷 648-656页

作者：程明石永久王元清 Key Laboratory of Structural Engineering and Vibration of Ministry of Education Department of Civil EngineeringTsinghua University

Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis （FEA）. The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.

关键词： aluminum bending member residual deformation plastic adaptation coefficient load-deflection relationship nonlinear fitting

Validation of a steel dual-core self-centering brace （DC-SCB） for seismic resistance： from brace member to one-story one-bay braced frame tests

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Frontiers of Structural and Civil Engineering 2016年第3期10卷 303-311页

作者： Chung-Che CHOU Ping-Ting CHUNG Tsung-Han WU Alexis Rafael Ovalle BEATO Department of Civil Engineering Taiwan University Taipei Taiwan China Director Center for Earthquake Engineering Research (CEER) Taiwan University Taipei Taiwan China

A steel dual-core self-centering brace （DC-SCB） is an innovative structural member that provides both energy dissipation and self-centering properties to structures, reducing maximum and residual drifts of structures in earthquakes. The axial deformation capacity of the DC-SCB is doubled by a parallel arrangement of two inner cores, one outer box and two sets of tensioning elements. This paper presents cyclic test results of a DC-SCB component and a full- scale one-story, one-bay steel frame with a DC-SCB. The DC-SCB that was near 8 m-long was tested to evaluate its cyclic behavior and durability. The DC-SCB performed well under a total of three increasing cyclic loading tests and 60 low- cycle fatigue loading tests without failure. The maximum axial load of the DC-SCB was near 1700 kN at an interstory drift of 2.5%. Moreover, a three-story dual-core self-centering braced frame （DC-SCBF） with a single-diagonal DC-SCB was designed and its first-story, one-bay DC-SCBF subassembly specimen was tested in multiple earthquake-type loadings. The one-story, one-bay subassembly frame specimen performed well up to an interstory drift of 2% with yielding at the column base and local buckling in the steel beam; no damage of the DC-SCB was found after all tests. The maximum residual drift of the DC-SCBF caused by beam local buckling was 0.5% in 2.0% drift cycles.

关键词： dual-core self-centering brace （DC-SCB） braced frame tests residual deformation

Study of heat treatment parameters for large-scale hydraulic steel gate track

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Water Science and Engineering 2013年第4期6卷 423-432页

作者： Ping-zhou CAO Guang-zhong LIU Kai WU College of Civil and Transportation Engineering Hohai University

In order to enhance external hardness and strength, a large-scale hydraulic gate track should go through heat treatment. The current design method of hydraulic gate wheels and tracks is based on Hertz contact linear elastic theory, and does not take into account the changes in mechanical properties of materials caused by heat treatment. In this study, the heat treatment parameters were designed and analyzed according to the bearing mechanisms of the wheel and track. The quenching process of the track was simulated by the ANSYS program, and the temperature variation, residual stress, and deformation were obtained and analyzed. The metallurgical structure field after heat treatment was predicted by the method based on time-temperatuxe-transformation （TTT） curves. The results show that the analysis method and designed track heat treatment process are feasible, and can provide a reference for practical projects.

关键词： steel gate track heat treatment parameter residual deformation numerical simulation

Dynamic Behaviour of a Caisson Quaywall Under Strong Earthquake

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China Ocean Engineering 1999年第1期14卷 47-62页

作者： Liu, HL Dai, HC Iai, S Hohai Univ Geotech Engn Res Inst Nanjing 210098 Peoples R China China Yangtze Three Gorges Project Dev Corp Yichang 443002 Peoples R China Minist Transport Port & Harbour Res Inst Nagase 239 Japan

Effective stress analysis is performed to evaluate the residual displacement of a caisson quaywall during 1994 Hokkaido- Toho- Oki Earthquake and 1993 Kushiro- Oki Earthquake. The constitutive model used in this study is a multiple shear mechanism type defined in strain space and can take into account the effect of rotation of principal stress axis. The earthquake accelerations recorded at the outcropping rock during the earthquake are used as input bedrock motion. The results of finite element analysis are in good agreement with the observed behaviour of the quaywall. The analysis also indicates that liquefaction and high excess porewater pressure have a significant effect on the deformation of the caisson. Soil improvement is speculated as the most reliable measures against liquefaction. The influence of soil improvement and the reasonable improved area are discussed in the paper.

关键词： caisson quaywall effective stress analysis lique faction residual deformation

Pore Water Pressure Buildup Under Cyclic Rotation of Principal Stress and Stability Evaluation of Seabed Deposit

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China Ocean Engineering 1994年第4期9卷 471-482页

作者： Shen Ruifu , Wang Hongjin , Zhou Jinxing and Zhou Keji Former graduate student of Tsinghua University, now works in Nanjing Hydraulic Research Institute, Nanjing 210029Professor, Tsinghua University, Beijing 100084 Senior Engineer, Tsinghua University, Beijing 100084

The cyclic rotation of principal stress direction with a constant amplitude is the characteristics of cyclic stress in seabed deposit induced by travelling waves. Presented in the paper are the results obtained from tests simulating the cyclic stress characteristics, with emphasis laid on the buildup of pore water pressure in soil samples. Regression analysis of test data shows that the pore water pressure can be expressed as the function of the number of cycles of cyclic loading, or as the function of generalized shear strain. Using the results thus obtained, the possibility of failure of seabed deposit under cyclic loading induced by travelling waves can be evaluated. The comparison with the results of conventional cyclic torsional shear tests shows that neglect of the effect of the cyclic rotation of the principal stress direction will result in considerable over-estimation of the stability of seabed deposit.

关键词： rotation of principal stress direction pore water pressure generalized shear strain residual deformation

residual Stresses in Spray Quenched EW75 Magnesium Alloy

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Residual Stresses in Spray Quenched EW75 Magnesium Alloy