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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 20742 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

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

NUMERICAL MODEL FOR FLOW MOTION WITH VEGETATION

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Journal of Hydrodynamics 2008年第2期20卷 172-178页

作者： zhang Jian-tao SU Xiao-hui department of civil and Hydraulic engineering Dalian University of Technology Dalian 116023 China department of civil engineering National University of Singapore Singapore 119260 Singapore

A set of governing equations for turbulent flows in vegetated area were derived with the assumption that vegetation is of straight and rigid cylinder. The effect of vegetation on flow motion was represented by additional inertial and drag forces. The new model was validated by available experimental data for open channel flows passing through vegetated areas with different vegetation size, density and distribution. Numerical results are in good agreement with the experimental data. Finally, the flow around a supposed isolated vegetated pile was simulated and the effects of vegetation density on the wake flow were discussed. It is found that the presence of vegetation, even at a very low density, has the pronounced influence on the dissipation of flow energy, both inside the vegetation domain and outside it in the wake flow region.

关键词： numerical simulation vegetation open channel

COMPUTATION OF FREE SURFACE FLOWS WITH HIGH RESOLUTION FINITE ELEMENT SCHEME

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Journal of Hydrodynamics 2003年第3期15卷 22-27页

作者： Jin Sheng, zhang Ri-xiang, Pu Gao-jun department of civil engineering, State Key Laboratory of Offshore engineering, Dalian university of Technology, Dalian 116024, China, departmentofcivilengineering StateKeyLaboratoryofOffshoreEngineeringDalianUniversityofTechnologyDalian116024China

A high-resolution finite element scheme is developed for the computation offree surface problems. The present higher-order accuracy scheme is obtained through the introductionof the difference of almost equal amount of diffusion and antidiffusion, where the antidiffusion isformulated as approximation to diffusion making use of consecutive gradient. The non-oscillatoryproperties are secured by limiters to preserve positivity constraints. The implement of the schemeis based on semi-discrete form and can be considered as reconstruction of the coefficient matrix ofalgebraic system, so, it can he conveniently used by either structured or unstructured meshes. Thepower and flexibility of the present high resolution VOF-FEM approach is validated by examplesincluding convective transport, dam breaking flow, and stilling basin flow in hydraulic engineering.

关键词： free surface flow high resolution finite element scheme

HYDRODYNAMICS OF FRACTAL FLOCS DURING SETTLING

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Journal of Hydrodynamics 2009年第3期21卷 347-351页

作者： zhang Jin-feng zhang Qing-he School of civil engineering Key Laboratory of Harbour and Ocean Engineering Ministry of Education Tianjin University Tianjin 300072 China department of Ocean and Resources engineering University of Hawaii at Manoa HI 96822 USA

The settling and hydrodynamic properties of 3-D fractal flocs in quiescent water are investigated with a numerical model based on the Lattice Boltzmann Method （LBM）, with considering the settling velocity, hydrodynamic drag force and infra-floc flow. The comparisons of floc settling velocities and effective densities indicate that the numerical results present good agreements with observations in field and at laboratory. The results show that the drag force Fo increases with the floc size dr according to the relationship FD ∝ df^3. Moreover, the intra-floc flow field and movement of the pore water provide a better understanding of the intra-floc flow from the microscopic viewpoint. The results also indicate that the lattice Boltzmann method is a promising approach to reveal the mechanisms of the flocculation in aquatic environments.

关键词： Lattice Boltzmann Method (LBM) fractal floc hydrodynamic properties drag force infra-floc flow

Guided wave propagation in multilayered piezoelectric structures

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Science China(Physics,Mechanics & Astronomy) 2009年第7期52卷 1094-1104页

作者： GUO YongQiang1, CHEN WeiQiu2,3 & zhang YongLiang4 1 Key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education, and School of civil engineering and Mechanics, Lanzhou university, Lanzhou 730000, China 2 Key Laboratory of Soft Soils and Geoenvironmental engineering, Ministry of Education, and department of civil engineering, Zhejiang university, Hangzhou 310058, China 3 department of engineering Mechanics, Zhejiang university, Hangzhou 310027, China 4 School of civil engineering, Lanzhou Jiaotong university, Lanzhou 730070, China Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education and School of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000 China Key Laboratory of Soft Soils and Geoenvironmental engineering Ministry of Education and Department of Civil Engineering Zhejiang University Hangzhou 310058 China department of engineering Mechanics Zhejiang University Hangzhou 310027 China School of civil engineering Lanzhou Jiaotong University Lanzhou 730070 China

A general formulation of the method of the reverberation-ray matrix (MRRM) based on the state space formalism and plane wave expansion technique is presented for the analysis of guided waves in multilayered piezoelectric structures. Each layer of the structure is made of an arbitrarily anisotropic piezoelectric material. Since the state equation of each layer is derived from the three-dimensional theory of linear piezoelectricity, all wave modes are included in the formulation. Within the framework of the MRRM, the phase relation is properly established by excluding exponentially growing functions, while the scattering relation is also appropriately set up by avoiding matrix inversion operation. Consequently, the present MRRM is unconditionally numerically stable and free from computational limitations to the total number of layers, the thickness of individual layers, and the frequency range. Numerical examples are given to illustrate the good performance of the proposed formulation for the analysis of the dispersion characteristic of waves in layered piezoelectric structures.

关键词： multilayered piezoelectric structures the method of reverberation-ray matrix guided waves dispersion characteristic

Refraction-Diffraction Model for Irregular Wave and Directional Spectrum Considering Current

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China Ocean engineering 1996年第2期11卷 193-202页

作者： Li Yucheng and zhang Yonggang Professor, department of civil engineering, Dalian university of Technology, Dalian 116023 Ph. D. Candidate, Dalian university of Technology, Dalian 116023 department of civil engineering Dalian University of Technology Dalian 116023 Dalian university of Technology Dalian 116023

A mild-slope equation for combined refraction and diffraction of random waves in the independent time current is derived using Kirby equation(1984). In the derivation, the frequency of random waves is represented based on the time series concept, by a typical frequency and its deviation part. Numerical results, compared with those of laboratory experiments, demonstrate that new set of irregular mild slope equation with current is of good adaptability.

关键词： wave rejraction-diff action irregular wave directional spectrum wave-current interaction simulation

One-dimensional numerical models of higher-order Boussinesq equations with high dispersion accuracy

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Acta Oceanologica Sinica 2003年第2期22卷 287-300页

作者： ZouZhili WangTao zhangXiaoli DarrenSpratt StateKeyLaboratoryofCoastalandOffshoreengineering DepartmentofCivilEngineeringDalianUniversityofTechnologyDalian116024China civilandEnvironmentalengineering UniversityofIllinoisatUrbana-ChampaignChampaignUSA

Nonlinear water wave propagation passing a submerged shelf is studied experimentally and numerically. The applicability of the wave propagation model of higher-order Boussinesq equations derived by Zou (2000, Ocean engineering, 27, 557 - 575) is investigated. Physical experiments are conducted; three different front slopes (1:10, 1 = 5 and 1:2) of the shelf are set-up in the experiment and their effects on the wave propagation are investigated. Comparisons of the numerical results with test data are made and the higher-order Boussinesq equations agree well with the measurements since the dispersion of the model is of high accuracy. The numerical results show that the good results can also be obtained for the steep-slope cases although the mild-slope assumption is employed in the derivation of the higher-order terms in the higher-order Boussinesq equations.

关键词： Water waves Boussinesq nonlinear dispersion

Currents induced by vertical varied radiation stress in standing waves and evolution of the bed composed of fine sediments

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International Journal of Sediment Research 2009年第2期24卷 214-226页

作者： Jing-Xin zhang1 and Hua LIU21 Lecturer,department of engineering Mechanics,School of Naval Architecture,Ocean and civil engineering,Shanghai Jiao Tong university,800 Dongchuan Road,Shanghai 200240,China 2 department of engineering Mechanics,School of Naval Architecture,Ocean and civil engineering,Shanghai Jiao Tong university,800 Dongchuan Road,Shanghai 200240,China [a]department of engineering Mechanics School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China [b]Department of Engineering Mechanics School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China

This paper extends the conventional concept of radiation stress(Longuet-Higgins and Stewart,1964) in progressive water waves to standing waves,so that its vertical profile could be defined and calculated in a new technical way. The hydrodynamic numerical model being coupled with the vertically varying radiation stress in standing waves is used to simulate the currents being induced by standing waves in the vertical section. Numerical modeling of suspended sediment transport is then carried out to simulate the evolution of the bed composed of fine sediments by the currents. The scour and deposition patterns simulated are in qualitative agreement with prior laboratory and field observations.

关键词： Standing wave Vertical variation in radiation stress Scour pattern Suspended sediment