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Dynamic shear modulus and damping ratio characteristics of undisturbed marine soils in the Bohai Sea,China

Earthquake Engineering and Engineering Vibration 2022年第2期21卷 297-312页

作者： Zhang Yan Zhao Kai Peng Yanjv Chen Guoxing Institute of Geotechnical Engineering Nanjing Tech UniversityNanjing 210009China Civil Engineering and Earthquake Disaster Prevention Center of Jiangsu Province Nanjing 210009China National Institute of Natural Hazards Ministry of Emergency ManagementBeijing 100085China

This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,*** is placed on the major factors for predominating the dynamic shear modulus(G)and damping ratio(λ)in the shear strain amplitude(γ_(a))from 10^(-5) to 10^(-2),involving depth,sedimentary facies types,and water content of marine *** empirical equations of the small-strain shear modulus(G_(max))and damping ratio(λ_(min))using a single-variable of depth H are established for the three marine soils.A remarkable finding is that the curves of shear modulus reduction(G/G_(max))and the damping ratio(λ)with increasing γ_(a) of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content *** finding is validated by independent experimental data from the *** the similar depths,the G value of the marine soils of terrestrial facies is the largest,followed b_(y) the neritic facies,and the G value of the marine soils of abyssal facies is the *** sedimentary facies types of the marine soils have slight effect on theλ*** significant finding is that the shear modulus reduction curves plotted against the γ_(a) of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils,while the damping curves plotted against γ_(a) are just the *** results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data.

关键词： Bohai Sea marine sediments dynamic shear modulus damping ratio sedimentary facies

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Modal parameter identification and damping ratio estimation from the full-scale measurements of a typical Tibetan wooden structure

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 681-695页

作者： Dai Lu Yang Na S.S.Law Yang Qingshan School of Civil Engineering Beijing Jiaotong University

Tibetan heritage buildings have a high historical and cultural value. They have endured adverse environmental loadings over hundreds of years without significant damage. However, there are few reports on their structural characteristics under normal environmental loadings and their behavior under dynamic loadings. In this research, a typical Tibetan wooden wall-frame building is selected to study its dynamic characteristics. Field measurements of the structure were conducted under environmental excitation to collect acceleration responses. The stochastic subspace identification （SSI） method was adopted to calculate the structural modal parameters and obtain the out-of-plane vibration characteristics of the slab and frames. The results indicated that the wall-frame structure had a lower out-of-plane stiffness and greater in-plane stiffness due to the presence of stone walls. Due to poor identified damping ratio estimates from the SSI method, a method based on the variance upper bound was proposed to complement the existing variance lower bound method for estimating the modal damping ratio to address the significant damping variability obtained from different points and measurements. The feasibility of the proposed method was illustrated with the measured data from the floor slab of the structure. The variance lower and upper bound methods both provided consistent results compared to those from the traditional SSI method.

关键词： Tibetan wooden structure field test modal parameters damping ratio variance upper/lower bound

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Estimation of damping ratio of soil sites using microtremor

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Earthquake Engineering and Engineering Vibration 2002年第1期1卷 45-49页

作者：郭迅黄玉龙袁一凡 Institute of Engineering Mechanics China Seismological BureauHarbin 150080China Professor Department of Civil and Structural Engineering The Hong Kong Polytechnic UniversityHong KongChina Associate Professor

It is widely known that the seismic response characteristics of a soil site depends heavily on several key dynamic properties of the soil stratum,such as predominant frequency and damping ratio.A widely used method for estimating the predominant frequency of a soil site by using microtremor records,proposed by Nakamura,is investigated to determine its effectiveness in estimating the damping *** authors conducted some microtremor measurements of soil sites in Hong Kong and found that Nakamura's method might also be used to estimate the damping ratio of a soil *** ratio data from several typical soil sites were obtained from both Nakamura's ratio curves using the half power point method and resonant column *** analysis indicates that there is a strong correlation between the damping ratios derived from these two different approaches.

关键词： microtremor predominant frequency damping ratio

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Influence of repeated freeze-thaw on dynamic modulus and damping ratio properties of silty sand

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Research in Cold and Arid Regions 2013年第5期5卷 572-576页

作者： TianLiang Wang Chao Ma Han Yan JianKun Liu School of Civil Engineering Shijiazhuang Tiedao University Key Laboratory of Roads and Railway Engineering Safety Control of Ministry of Education Shijiazhuang Tiedao University School of Civil Engineering Beijing Jiaotong University Northwest Corporation China Railway Construction Engineering Group

Under repeated freezing and thawing in deep seasonal frozen regions, the stability and strength of the soil are imposed in the form of large uneven settlement, instability and strength reduction, which affect the normal operation of railway lines. This study is to obtain the influencing rules of freeze-thaw on the dynamic properties （dynamic strain, confining pressure and compactness） of silty sand. Based on an amount of inner tests, the dynamic modulus and damping ratio properties of silty soil subjected to repeated freeze-thaw cycles were deeply researched and analyzed. The results are as follows： At the same dynamic strain, the relationship of dynamic stress and freeze-thaw cycles presents negative cor- relation, and the relationship of dynamic stress, confining pressure and compactness present positive correlation. The dynamic modulus double decreases while the damping ratio double increases with incremental increase in dynamic strain. The dynamic modulus sharply decreases while the damping ratio increases with incremental increase in freeze-thaw cycles, and then the changes level off after six freeze-thaw cycles. The dynamic modulus increases while the damping ratio decreases as the confining pressure and compactness increase at the same strain level.

关键词： freeze-thaw cycles silty sand dynamic modulus damping ratio

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Physical　mechanism　of　the　chaotic　detection　of　the　unknown　frequency　of　weak　harmonic　signal　and　effects　of　damping　ratio　on　the　detection　results

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Chinese Physics B 2004年第9期13卷 1386-1390页

作者：李月杨宝俊邓小英金雷杜立志 DepartmentofInformationEngineering JilinUniversityChangchun130012China CorrespondenceshouldbeaddressedtoYangBao-jun

In the zero-order approximation, we use the perturbation method of parameter with small magnitude to prove that the harmonic frequency in the solution of the equation is close to that of the driving force when the chaotic system from Duffing-Holmes equation stays in the stable periodic state, which is the physical mechanism of the detection of the unknown frequency of weak harmonic signal using the chaotic theory. The result of the simulation experiment shows that the method proposed in this paper, by which one can determine the frequency of the stable system from the number of circulation change of the phase state directionally across a fixed phase state point (x, x) in fixed simulation time period, is successful. Analyzing the effects of the damping ratio on the chaotic detection result, one can see that for different frequency ranges it is necessary to carefully choose corresponding damping ratio α.

关键词： weak harmonic signal unknown frequency chaotic detection damping ratio

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Influence of Trailing-Edge Wear on the Vibrational Behavior of Wind Turbine Blades

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Fluid Dynamics & Materials Processing 2024年第2期20卷 337-348页

作者： Yuanjun Dai Xin Wei Baohua Li Cong Wang Kunju Shi Mechanical College Shanghai Dian Ji UniversityShanghai201306China College of Energy Engineering Xinjiang Institute of EngineeringUrumqi830091China

To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal *** to these experiments,the natural frequencies of trailing-edge worn blades-1,-2,and-3 increase the most in the second to fourth order,theﬁfth order increases in the middle,and theﬁrst order increases the *** damping ratio data indi-cate that,in general,theﬁrstﬁve-order damping ratios of trailing-edge worn blades-1 and trailing-edge worn blades-2 are reduced,and theﬁrstﬁve-order damping ratios of trailing-edge worn blades-3 are slightly *** mode shape diagram shows that the trailing-edge worn blades-1 and-2 have a large swing in the tip and the blade,whereas the second-and third-order vibration shapes of the trailing edge-worn blade-3 tend to be ***,all these results reveal that the blade’s mass and the wear area are the main fac-tors affecting the vibration characteristics of wind turbine blades.

关键词： Wind turbine modal test natural frequency damping ratio mode shape

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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

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COMPUTATION OF FREQUENCIES AND damping ratioS FOR ADAPTIVE STRUCTURES

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Applied Mathematics and Mechanics(English Edition) 1999年第6期20卷 109-116页

作者：张连文夏人伟曾广武 Laboratory of Ship Structure Design Faculty of Traffic Science and Engineering Huazhong University of Science and Technology 430074 Wuhan P R China Faculty Space Navigation 100083 Beijing Beijing University of Aeronautics and Astronautics P R China

ＩｎｔｒｏｄｕｃｔｉｏｎＡｌｏｎｇｗｉｔｈｔｈｅｒｅｃｅｎｔａｄｖａｎｃｅｓｏｆｈｉｇｈｔｅｃｈｎｏｌｏｇｉｅｓ，ａｄａｐｔｉｖｅｓｔｒｕｃｔｕｒｅｓａｒｅｐｌａｙｉｎｇａｇｒｅａｔｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｓｐ... 详细信息

ＩｎｔｒｏｄｕｃｔｉｏｎＡｌｏｎｇｗｉｔｈｔｈｅｒｅｃｅｎｔａｄｖａｎｃｅｓｏｆｈｉｇｈｔｅｃｈｎｏｌｏｇｉｅｓ，ａｄａｐｔｉｖｅｓｔｒｕｃｔｕｒｅｓａｒｅｐｌａｙｉｎｇａｇｒｅａｔｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｓｐａｃｅｄｅｖｅｌｏｐｍｅｎｔ［１～...

关键词： active member adaptive structure damping ratio frequency frequency damping ratio state vector approach V414.33

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Dynamic properties of polyurethane foam adhesive-reinforced gravels

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Science China(Technological Sciences) 2021年第3期64卷 535-547页

作者： LIU Ping MENG MinQiang XIAO Yang LIU HanLong YANG Gui School of Civil Engineering Ludong UniversityYantai 264025China School of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China

Polyurethane foam adhesive(PFA)has been introduced as an alternative stabilizer in geotechnical applications because PFA can improve the engineering characteristics of soil by filling the pore space and generating adhesive bonding among the ***,the dynamic properties of PFA-reinforced soils are not well *** analyze the dynamic characteristics of PFA-reinforced gravels,a series of cyclic triaxial tests were carried out to investigate the shear modulus and damping ratio of PFA-reinforced gravels,and to determine the corresponding effects of the PFA content,confining pressure,consolidation stress ratio and loading *** results showed that the shear modulus increased,and the damping ratio decreased as the PFA content,confining pressure and consolidation stress ratio *** contrast,the effect of the loading frequency,which ranged from 0.05 to 1 Hz,was negligible.A modified hyperbolic empirical model can consider the effect of the PFA content on the maximum shear modulus and predict the relationship between the normalized shear modulus and the normalized shear strain was ***,the upper and lower bounds of the damping ratio were also proposed.

关键词： polyurethane foam adhesive gravel shear modulus damping ratio cyclic triaxial test

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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

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