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Structural vibration passive control and economic analysis of a high-rise building in Beijing

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Earthquake Engineering and Engineering Vibration 2009年第4期8卷 561-568页

作者： Chen Yongqi Cao Tiezhu Ma Liangzhe Luo Chaoying Beijing Qitai Shock Control and Scientific Development Co. Ltd Beijing 10003 7 China John A. Martin ＆ Associates Inc. Los Angeles USA

Performance analysis of the Pangu Plaza under earthquake and wind loads is described in this paper. The plaza is a 39-story steel high-rise building, 191 m high, located in Beijing close to the 2008 Olympic main stadium. It has both fluid viscous dampers （FVDs） and buckling restrained braces or unbonded brace （BRB or UBB） installed. A repeated iteration procedure in its design and analysis was adopted for optimization. Results from the seismic response analysis in the horizontal and vertical directions show that the FVDs are highly effective in reducing the response of both the main structure and the secondary system. A comparative analysis of structural seismic performance and economic impact was conducted using traditional methods, i.e., increased size of steel columns and beams and/or use of an increased number of seismic braces versus using FVD. Both the structural response and economic analysis show that using FVD to absorb seismic energy not only satisfies the Chinese seismic design code for a ＂rare＂ earthquake, but is also the most economical way to improve seismic performance both for one-time direct investment and long term maintenance.

关键词： fluid viscous dampers (FVD) damping ratio secondary system One-time investment maintenance factor

Accuracy of the half-power bandwidth method with a third-order correction for estimating damping in multi-DOF systems

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 33-38页

作者： Wang Jinting Lü Dandan Jin Feng Zhang Chuhan State Key Laboratory of Hydroscience and Engineering Tsinghua University

A third-order correction was recently suggested to improve the accuracy of the half-power bandwidth method in estimating the damping of single DOF *** paper analyzes the accuracy of the half-power bandwidth method with the third-order correction in damping estimation for multi-DOF linear *** ratios in a two-DOF linear system are estimated using its displacement and acceleration frequency response curves,respectively.A wide range of important parameters that characterize the shape of these response curves are taken into *** show that the third-order correction may greatly improve the accuracy of the half-power bandwidth method in estimating damping in a two-DOF *** spite of this,the half-power bandwidth method may significantly overestimate the damping ratios of two-DOF systems in some cases.

关键词： half-power bandwidth method third-order correction damping ratio estimation error two-DOF system

Experimental study on cyclic deformation properties of saturated Fujian sand at different loading frequencies

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Underground Space 2023年第6期13卷 150-165页

作者： Chong Yue Ke Liang Chengshun Xu Xiuli Du Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education Beijing University of TechnologyBeijing 100124China

In this study,a series of undrained cyclic torsional shear tests were conducted to investigate the effect of cyclic loading frequency f on the pre-liquefaction(shearing contractive(SC)period and initial shearing dilative(ISD)period)and post-liquefaction(late shearing dilative(LSD)period)deformation properties of saturated Fujian *** secant shear modulus G and damping ratioλin the entire cyclic loading process,and the unloading tangent shear modulus G_(L1)and flow deformation tangent shear modulus GL2 in the ISD and LSD periods were adopted to quantitatively characterize the evolution of hysteresis loop with an increase in shear strain amplitude *** test results show that the effect of f on G of saturated Fujian sand in the SC period is not ***,all the G-γ_(a),G_(L1)-γ_(a),and GL2-ca curves in the ISD and LSD periods showed a downward trend with an increase in *** study also proposes a modified method for calculatingλto compensate for the analytical error caused by the non-closure of hysteresis *** with the classical curves that mainly applied in geotechnical engineering,theλfirst increases and then decreases with the increase ofγ***,theλevaluated by the modified method is approximately 10%–15%more than theλevaluated by the traditional method when theλreaches its peak value.

关键词： Sand liquefaction Cyclic loading frequency Hysteresis loop shape Shear modulus damping ratio

Test and numerical investigations on static and dynamic characteristics of extra-wide concrete self-anchored suspension bridge under vehicle loads

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Journal of Central South University 2017年第10期24卷 2382-2395页

作者： ZHOU Guang-pan LI Ai-qun LI Jian-hui DUAN Mao-jun School of Civil Engineering Southeast University Beijing Advanced Innovation Centre for Future Urban Design Beijing University of Civil Engineering and Architecture School of Civil Engineering Nanjing Forestry University

The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric tra

关键词： self-anchored suspension bridge extra-wide girder field test simulation vehicle loads increments distribution damping ratio mode shape dynamic impact coefficient

3D Effects on Vortex-Shedding Flow and Hydrodynamic Coefficients of A Vertically Oscillating Cylinder with A Bottom-Attached Disk

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China Ocean Engineering 2017年第4期31卷 428-437页

作者： WANG Quan KOU Yu-feng ZHU Ren-qing CHEN Hong State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai 200240China School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhengjiang 212002China Shanghai Waigaoqiao Shipbuilding CO. LTD.Shanghai 200240China

Vortex-shedding flow induced by the vertical oscillation of a cylinder with bottom-attached disks of different diameter ratio Dd/Dc and thickness ratio td/Dc is studied by a 3D （three-dimensional） numerical model developed in this paper, and compared with the results obtained through 2D （two-dimensional） numerical model. The high-order upwind scheme is applied to stabilize the computation, and convergence is accelerated by the multi-grid method. Qualitative and quantitative analyses of the differences between the 2D and 3D simulation results reveal the 3D effect on the flow field characteristics and hydrodynamic coefficients of the vertically oscillating cylinder with a bottom-attached disk. The 3D effect on the fluid field is mainly reflected in the significance of three vortex-shedding patterns： ωx has a greater effect on the flow fields around the sharp edges relative to the vortices generated in the 2D simulation. In the slice along the axial orientation, the vortex effect of ωy along the radial axis is smaller than that of ωx along the circumferential direction, indicating the radial effect on the velocity more pronounced than the circumferential effect around the sharp edges of the disk. The rotational interaction ωz of the fluid in the horizontal plane during the heave motion is insignificant. Based on the 2D and 3D simulation results, the turning points that separate the increasing regimes of the added mass coefficient and damping ratio are identified. The dependence of the turning point on the diameter ratio Dd/Dc and thickness ratio td/Dc are discussed in detail.

关键词： 3D effect vortex-shedding pattern added mass coefficient damping ratio vertical oscillation

A Novel Approach to Predict the Stability Limits of Combustion Chambers with Large Eddy Simulation

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Journal of Thermal Science 2010年第3期19卷 261-265页

作者： B.Pritz F.Magagnato M.Gabi Department of Fluid Machinery University of Karlsruhe Kaiserstr.1276131 KarlsruheGermany

Lean premixed combustion,which allows for reducing the production of thermal NOx,is prone to combustion *** is an extensive research to develop a reduced physical model,which allows-without time-consuming measurements-to calculate the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum,combustion chamber).For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) were carried *** these investigations the flow in the combustion chamber is isotherm,non-reacting and excited with a sinusoidal mass flow *** a combustion chamber as a single resonator subsequently a coupled system of a burner plenum and a combustion chamber were *** this paper the results of additional investigations of the single resonator are *** flow in the combustion chamber was investigated without excitation at the *** was detected,that the mass flow rate at the outlet cross section is pulsating once the flow in the chamber is *** fast Fourier transform of the signal showed that the dominant mode is at the resonance frequency of the combustion *** result sheds light on a very important source of self-excited combustion *** the LES can provide not only the damping ratio for the analytical model but the eigenfrequency of the resonator also.

关键词： compressible large-eddy simulation combustion instabilities oscillating flow damping ratio

Operational Mode Identification Based on Sliding Time Window Method and Eigensystem Realization Algorithm

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第5期36卷 838-844页

作者： WANG Liang ZHANG Yan CAI Yipeng NANGONG Zijun China Academy of Launch Vehicle Technology

The identification result of operational mode is eurychoric while operational mode identification is investigated under ambient excitation,which is influenced by the signal size and the time *** operational mode identification method,which is based on the sliding time window method and the eigensystem realization algorithm(ERA),is investigated to improve the identification accuracy and ***,the theory of the ERA method is ***,the strategy for decomposition and implementation is put forward,including the sliding time window method and the filtration method of *** last,an example is studied,where the model of a cantilever beam is built and the white noise exciting is *** show that the operational mode identification method can realize the modes,and has high robustness to the signal to noise ratio and signal size.

关键词： mode identification robust eigensystem realization algorithm(ERA) operational mode damping ratio

Impact of train speed on the mechanical behaviours of track-bed materials

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 818-829页

作者： Francisco Lamas-Lopez Yu-Jun Cui Nicolas Calon Sofia Costa D’Aguiar Tongwei Zhang Laboratoire Navier/CERMES Ecole des Ponts ParisTech Marne-la-Vallée 77455 France Département Ligne Voie et Environnement SNCF-Engineering La Plaine St. Denis 93574 France Division Auscultation Modélisation & Mesures SNCF-Research & Development Paris 75012 France

For the 30,000 km long French conventional railway lines(94% of the whole network),the train speed is currently limited to 220 km/h,whilst the speed is 320 km/h for the 1800 km long high-speed ***,there is a growing need to improve the services by increasing the speed limit for the conventional *** paper aims at studying the influence of train speed on the mechanical behaviours of track-bed materials based on field monitoring *** is put on the behaviours of interlayer and subgrade *** selected experimental site is located in Vierzon,*** sensors including accelerometers and soil pressure gauges were installed at different *** vertical strains of different layers can be obtained by integrating the records of accelerometers installed at different trackbed *** experimentation was carried out using an intercity test train running at different speeds from 60 km/h to 200 km/*** test train was composed of a locomotive(22.5 Mg/axle) and 7 'Corail'coaches(10.5 Mg/axle).It was observed that when the train speed was raised,the loadings transmitted to the track-bed ***,the response of the track-bed materials was amplified by the speed rise at different depths:the vertical dynamic stress was increased by about 10% when the train speed was raised from 60 km/h to 200 km/h for the locomotive loading,and the vertical strains doubled their quasistatic values in the shallow ***,the stressestrain paths were estimated using the vertical stress and strain for each train *** loading paths allowed the resilient modulus Mrto be *** was found that the resilient modulus(M_r) was decreased by about 10% when the train speed was increased from 100 km/h to 200 km/***,the damping ratio(D_r) kept stable in the range of speeds explored.

关键词： Field experimentation Conventional track-bed materials Train speed upgrade Mechanical behaviours Reversible modulus damping ratio

Dynamic behavior of sandwich beams with different compositions of magnetorheological fluid core

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International Journal of Smart and Nano Materials 2021年第1期12卷 88-106页

作者： Subash Acharya Vipin J Allien Puneet N P Hemantha Kumar Department of Mechanical Engineering NITK SurathkalMangaloreKarnatakaIndia

Magnetorheological fluid(MRF)sandwich beams belong to a class of adaptive beams that consists of MRF sandwiched between two or more face layers and have a great prospective for use in semi-active control of beam vibrations due to their superior vibration suppression *** composition of MRF has a strong influence on the MRF properties and hence affects the vibration characteristics of the *** this work,six MRF samples(MRFs)composed of combination of two particle sizes and three weight fractions of carbonyl iron pow-der(CIP)were prepared and their viscoelastic properties were *** MRFs were used to fabricate different MRF core sandwich ***,a sandwich beam with commer-cially available MRF 132DG fluid as core was *** modal parameters of the cantilever MRF sandwich beams were determined at different magnetic ***,sinusoidal sweep excitation tests were performed on these beams at different magnetic fields to investigate their vibration suppres-sion *** having larger particle size and higher weight fraction of CIP resulted in higher damping ratio and vibration ***,optimal particle size and weight fraction of CIP were determined based on the maximization of damping ratio and minimization of weight of MRF.

关键词： Smart materials adaptive sandwich beam damping ratio vibration suppression complex shear modulus