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Irregular-Mode Cracking in Fe-3 wt pct Si Alloy

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Journal of Materials Science & Technology 2005年第3期21卷 338-342页

作者： Y.Qiao department of civil engineering, University of Akron, Akron, OH 44325-3905, USA department of civil engineering University of Akron Akron OH 44325-3905 United States

Due to the non-uniform nature of crack advance, when a cleavage front encounters a high-angle grain boundary, instead of simultaneous break-through along the whole boundary, the front transmission mode can be irregular, which results in a higher fracture resistance and a tortuous percolation behavior. In this paper, this phenomenon is studied quantitatively through the analysis on the work of separation and the change in strain energy for an Fe-3 wt pct Si alloy. The influences of the crystallographic misorientations, the break-through mode, the cleavage front profile, and the grain boundary properties are discussed in detail.

关键词： Fracture toughness Transgranular Iron-silicon alloy Irregular mode

Some Consideration on Elastic Pile Foundation Analysis by Poulos

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岩石力学与工程学报 2001年第6期20卷 882-885页

作者： Cheng Yungming (department of civil and Structural engineering, The Hong Kong Polytechnic University, Hong Kong, China) 香港工业大学香港

The elastic pile foundation analysis by Poulos is well developed and has been adopted by some countries in their design guideline. In die vertical load analysis, the author has discovered that the approach by Poulos is sensitive to the number of segments used fix-analysis and can lead to some unreasonable results for pile in finite depth of soil. In the lateral load analysis, the group interaction factor which is claimed to be a linear relation of the departure angle β by Poulos is found to be a linear relation of sin2 β by the author.

关键词： pile elastic analysis vertical and horizontal load

Self-centering seismic retrofit scheme for reinforced concrete frame structures:SDOF system study

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Earthquake engineering and engineering Vibration 2010年第2期9卷 271-283页

作者： Yunfeng Zhang and Xiaobin Hu department of civil and Environmental engineering,University of Maryland,College Park,MD 20742,USA department of civil and Environmental engineering University of Maryland College Park USA College Park USA

This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.

关键词： earthquake reinforced concrete frame structure nonlinear analysis SDOF system seismic retrofit self-centering

Diffraction of plane SV waves by a cavity in poroelastic half-space

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Earthquake engineering and engineering Vibration 2009年第1期8卷 29-46页

作者： Liang Jianwen and Liu Zhongxian department of civil engineering, Tianjin University, Tianjin 300072, China Professor PhD Candidate department of civil engineering Tianjin University Tianjin China

This paper presents an indirect boundary integration equation method for diffraction of plane SV waves by a 2-D cavity in a poroelastic *** Green＇s functions of compressive and shear wave sources are derived based on Biot＇s theory. The scattered waves are constructed using fictitious wave sources close to the boundary of the cavity, and their magnitudes are determined by the boundary conditions. Verification of the accuracy is performed by：（1） checking the satisfaction extent of the boundary conditions, （2） comparing the degenerated solutions of a single-phased case with well- known solutions, and （3） examining the numerical stability of the solutions. The nature of diffraction of plane SV waves around a cavity in a poroelastic half-space is investigated by numerical examples.

关键词： poroelastic half-space cavity diffraction plane SV waves compressive wave source shear wave source Green's function pore pressure

Conservation laws for mechanical systems with unilateral holonomic constraints

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Progress in Natural Science:Materials International 2004年第1期14卷 56-60页

作者： ZHANG Yi*(department of civil engineering, University of Science and Technology of Suzhou, Suzhou 215011, China) Univ Sci & Technol Suzhou Dept Civil Engn Suzhou 215011 Peoples R China

A general approach to the construction of conservation laws for mechanical systems with unilateral holonomic constraints by finding corresponding integrating factors is presented. The definition of integrating factors for the Routh equations of motion of the systems is given, and the necessary conditions for the existence of conserved quantities of the unilateral holonomic constraint systems are studied in detail. The conservation theorem and its inverse for the systems are established, and an example is given to illustrate the application of the results.

关键词： unilateral holonomic constraint integrating factor conservation theorem Killing equation

Analytical theory of flexural behavior of concrete beam reinforced with textile-combined steel

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Science China(Technological Sciences) 2010年第6期53卷 1700-1710页

作者： XU ShiLang & YIN ShiPing department of civil engineering,Dalian University of Technology,Dalian 116024,China department of civil engineering Dalian University of Technology Dalian China

Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become ***,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate *** the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover *** order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two *** cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are *** with the old one,the new structure has less dead weight and has the merits of service safety and good *** flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading *** between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.

关键词： textile-reinforced concrete limiting the crack beam reinforced with textile-combined steel flexural behavior analytical theory

A HIGHLY ACCURATE ρ METHOD FOR STRUCTURAL DYNAMIC ANALYSIS

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Acta Mechanica Sinica 1988年第3期4卷 265-274页

作者： Xie Minsheng department of civil engineering, Huaqiao University department of civil engineering Huaqiao University Quanzhou China

The paper proposes a ρ method of unconditionally stable direct integration with thefourth-order and fifth-order accuracy. The ρ method shows a good algorithmic damping and periodextension property, and we don’t find any "overshooting" phenomenon. It needs less calculation andstorage space than other methods of high accuracy. It doesn’t require that the damping matrix satisfythe condition of orthogonality of modes in order to prove its unconditional stability.

关键词： algorithmic damping period extension unconditionally stable

Importance Sampling Method in V-Space

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China Ocean engineering 1997年第2期12卷 127-150页

作者： Jin Weiliang Professor, department of civil engineering, Zhe Jiang University, Hangzhou 310027 department of civil engineering Zhejiang University Hangzhou 310027 China

Based on the observation of importance sampling and second order information about the failure surface of a structure, an importance sampling region is defined in V-space which is obtained by rotating a U-space at the point of maximum likelihood. The sampling region is a hyper-ellipsoid that consists of the sampling ellipse on each plane of main curvature in V-space. Thus, the sampling probability density function can be constructed by the sampling region center and ellipsoid axes. Several examples have shown the efficiency and generality of this method.

关键词： structural reliability Monte-Carlo simulation importance sampling method failure probability maximum likelihood curvature gradient

CONTACT FRICTION ANALYSIS AND STRESS OSCILLATION SUPPRESSION WITH A SIMPLE INTERFACE ELEMENT

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Acta Mechanica Solida Sinica 2000年第1期13卷 33-41页

作者： Lei Xiaoyan (department of civil engineering,East China Jiaotong University,Nanchang 330013,China) department of civil engineering East China Jiaotong University Nanchang 330013 China

A simple interface element for analyzing contact friction problems is developed. Taking nodal displacements and contact stresses as unknowns, this element can simulate frictional slippage, decoupling and re-bonding of two bodies initially mating or having gaps at a common interface. The method is based on the Finite Element Method and load incremental theory. The geometric and static constraint conditions on contact surfaces are treated as additional conditions and are included in stiffness equations. This simple element has the advantages of easy implementation into standard finite element programs and fast speed for convergence as well as high accuracy for stress distribution in interface. Undesirable stress oscillations are also investigated whenever large stress gradients exist over the contact surfaces. Exact integration or the conventional Gauss integration scheme used to evaluate the interpolation function matrix of the interface element is found to be the source of the oscillations. Eigenmode analysis demonstrates that the stress behavior of an interface element can be improved by using the Newton-Cotes integration scheme. Finally, the test example of a strip footing problem is presented.

关键词： contact friction interface element stress oscillation eigenmode analysis