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Homogenization-based multi-scale damage theory

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 690-698页

作者： LI Jie 1,2.& REN XiaoDan 1 1 School of Civil engineering, tongji university,{2., china 2.state key laboratory of disaster reduction in Civil engineering,{2., china 1. School of Civil engineering Tongji University Shanghai 200092 China2. State Key Laboratory of Disaster Reduction in Civil Engineering Shanghai 200092 China

The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonlinear structural analysis. Starting from the asymptotic expansion based homogenization theory, the multi-scale energy integration is proposed to bridge the gap between the micro and macro scales. By recalling the Helmholtz free energy based damage definition, the damage variable is represented by the multi-scale energy integration. Hence the damage evolution could be numerically simulated on the basis of the unit cell analysis rather than the experimental data identification. Finally the framework of the multi-scale damage theory is established by transforming the multi-scale damage evolution into the conventional continuum damage mechanics. The agree- ment between the simulated results and the benchmark results indicates the validity and effectiveness of the proposed theory.

关键词： Multi-scale damage representation asymptotic method constitutive model numerical simulation

Full-scale measurements of dynamic response of suspension bridge subjected to environmental loads using GPS technology

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Science china(Technological Sciences) 2010年第2期53卷 469-479页

作者： YI TingHua1,2. LI HongNan1 & GU Ming2.1state key {2. of Coastal and Offshore engineering, Dalian university of Technology, Dalian 11602., china 2.0} key {2. for disaster reduction in Civil engineering,{12., shanghai 200092, china 1. state key {2. of Coastal and Offshore engineering Dalian University of Technology Dalian 116024 China2. State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai 200092 China

Nowadays, there are many larger and taller engineering structures than in the past. These structures are commonly designed to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For the dynamic response prediction, finite element (FE) modal updating and structural health monitoring, the dynamic characteristics of a structure are becoming increasingly important. The aim of this paper is to show an emerging tool-the real time kinematic (RTK) global positioning system (GPS), which is used to measure and monitor the low-frequency vibration of Dalian BeiDa Bridge, a medium span suspension bridge. The modal analysis is firstly performed on the developed three-dimensional FE model according to the original blue prints of the bridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests using the accelerometers on the bridge deck are conducted just prior to the use of the GPS system in order to validate the FE model. And then, the calibration test is done to assess the dynamic displacement measurement accuracy of the GPS in three orthogonal directions. The GPS signal properties, such as the amplitude, standard deviations (STD), power spectral density (PSD), and probability density functions (PDF), are studied in details. After that, a structural health monitoring system based on the GPS is devised and installed on the bridge to provide real-time measurement of deck movement. The output-only modal parameter identification is carried out by using the Periodogram method to investigate the responses of the bridge. The result shows that the spectral densities of the displacements measured by the GPS correspond well with the results by the FEM analysis and the accelerometer vibration test. It is concluded that the GPS method is reliable and useful to clarify the ambient vibration response behaviors of the flexible structures. The integration of the GPS and accelerometer methods results in a hybrid arrangement tha

关键词： health monitoring global positioning system real-time kinematic suspension bridge modal analysis

Recent research and applications of GPS based technology for bridge health monitoring

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Science china(Technological Sciences) 2010年第10期53卷 2597-2610页

作者： YI TingHua1,2. LI HongNan1 & GU Ming2.1 Faculty of Infrastructure engineering, Dalian university of Technology, Dalian 11602.,{2. 2.state key laboratory for disaster reduction in Civil engineering, tongji university, shanghai 200092,{2. 1. Faculty of Infrastructure engineering Dalian University of Technology Dalian 116023 China2. State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai 200092 China

Today,long-span bridges are being designed to be more flexible and to resist extensive impacts from changes in temperature,severe wind gusts and earthquake tremors. Structural responses (especially displacement) of bridge structures are becoming increasingly important for the finite element (FE) modal updating,structural response prediction and safety evaluation. Methods of global displacement sensing were developed for these needs. This paper presents an overview of current research and development activities in the field of bridge health monitoring using the global positioning system (GPS). The GPS monitoring technology and its accuracy assessment method are also briefly described. Finally,existing problems and promising research efforts in the GPS based bridge health monitoring are discussed.

关键词： global positioning system (GPS) structural health monitoring (SHM) bridge measurement

Experimental investigation of damage behavior of RC frame members including non-seismically designed columns

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Earthquake engineering and engineering Vibration 2009年第2期8卷 301-311页

作者： Chen Linzhi,Lu Xilin,Jiang Huanjun and Zheng Jianbo state key {2. of disaster reduction in Civil engineering,tongji university,shanghai 200092,china PhD Candidate Professor Associate Professor Master of engineering state key {2. of disaster reduction in Civil engineering Tongji University Shanghai 200092 China state key {2. of disaster reduction in Civil engineering Tongji University 1239 Siping Road Shanghai 200092 China

Reinforced concrete （RC） frame structures are one of the mostly common used structural systems, and their seismic performance is largely determined by the performance of columns and beams. This paper describes horizontal cyclic loading tests often column and three beam specimens, some of which were designed according to the current seismic design code and others were designed according to the early non-seismic Chinese design code, aiming at reporting the behavior of the damaged or collapsed RC frame strctures observed during the Wenchuan earthquake. The effects of axial load ratio, shear span ratio, and transverse and longitudinal reinforcement ratio on hysteresis behavior, ductility and damage progress were incorporated in the experimental study. Test results indicate that the non-seismically designed columns show premature shear failure, and yield larger maximum residual crack widths and more concrete spalling than the seismically designed columns. In addition, longitudinal steel reinforcement rebars were severely buckled. The axial load ratio and shear span ratio proved to be the most important factors affecting the ductility, crack opening width and closing ability, while the longitudinal reinforcement ratio had only a minor effect on column ductility, but exhibited more influence on beam ductility. Finally, the transverse reinforcement ratio did not influence the maximum residual crack width and closing ability of the seismically designed columns.

关键词： reinforced concrete frame member cyclic test hysteresis behavior damage behavior seismic performance

REYNOLDS NUMBER EFFECTS IN TALL BUILDING WIND TUNNEL TESTS

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Journal of Hydrodynamics 1996年第4期8卷 56-62页

作者： Cheng Zhao Shi Zong-cheng Zhang Feng(state key Lab. for {2. reduction in Civil Eng., tongji Univ shanghai 200092, P.R. china) tongji Univ Shanghai China

In wind tunnel tests of tall building models comprised of rounded or streamlined surfaces, Reynolds Number Effects (RNE) may be remarkable. In most researches and projects, owing to the presence of sharp edged corners at model, RNE was often treated as negligible, and data colleCted in subcritical flow regime were applied directly to designs which were sure to be supercritical without any modification. But it was proved necessary to take RNE into consideration when a model had predominant rounded smooth surface(s). Some research activities were devoted to the mentioned condition and two experimental techniques accompanied by two wind tunnel model tests were introduced in the article. The authors also presented some amusing phenomenon such as extremely low pressure coefficients caused by the separating bubbles when now past sharp edged corners, unsymmetrical pressure coefficient distributions commenced by biased gap f'low (seen Figs. 3, 4) while models were placed symmetrically in the approaching flow.

关键词： Reynolds Number Effect wind tunnel simulation nows around building

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轴向约束钢框架柱火灾升温下屈曲后性能研究

同济大学学报（自然科学版） 2008年第4期36卷 438-443页

作者：王培军李国强同济大学土木工程学院上海200092

提出了一种改进的Jezék方法,用于火灾升温下轴向约束钢框架柱屈曲后性能分析,高温条件下钢材的应力-应变关系考虑了钢柱屈曲后凸侧可能出现的卸载现象.对轴向约束钢柱的参数分析表明,随着约束刚度的增大,钢柱附加轴力增大,屈曲温度降低... 详细信息

提出了一种改进的Jezék方法,用于火灾升温下轴向约束钢框架柱屈曲后性能分析,高温条件下钢材的应力-应变关系考虑了钢柱屈曲后凸侧可能出现的卸载现象.对轴向约束钢柱的参数分析表明,随着约束刚度的增大,钢柱附加轴力增大,屈曲温度降低,但轴向约束对屈曲后性能影响很小;荷载比大的构件抗火性能差,屈曲温度低,屈曲后轴力下降迅速;长细比小的构件,屈曲后轴力下降缓慢,屈曲后抗火性能显著提高;初弯曲大的构件,屈曲温度低,附加轴力小.在局部火灾下,利用约束钢柱的屈曲后性能,可显著提高其抗火性能.

关键词：钢框架柱火灾临界温度屈曲后性能轴向约束

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随机动力系统磁流变阻尼最优控制策略

同济大学学报（自然科学版） 2010年第2期38卷 164-169,177页

作者：彭勇波李杰同济大学土木工程防灾国家重点实验室上海200092 同济大学上海防灾救灾研究所上海200092

提出了基于广义密度演化方程的限界Hrovat半主动控制策略.以随机地震动作用下磁流变阻尼控制系统为研究对象,根据系统二阶统计量评价和跟踪实现目标主动最优控制力的控制准则,进行了磁流变液阻尼器的参数设计.数值结果表明在概率意义上... 详细信息

提出了基于广义密度演化方程的限界Hrovat半主动控制策略.以随机地震动作用下磁流变阻尼控制系统为研究对象,根据系统二阶统计量评价和跟踪实现目标主动最优控制力的控制准则,进行了磁流变液阻尼器的参数设计.数值结果表明在概率意义上,恰当设计的半主动控制器可以达到与主动控制器几乎相同的控制效果.同时,磁流变阻尼器表现出类似Bouc-Wen模型的动态阻尼性能,即强度退化、刚度退化和捏拢效应.

关键词：磁流变阻尼器随机最优控制广义密度演化方程限界Hrovat控制算法动态规划

Mining subsidence control by solid backfilling under buildings

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中国有色金属学会会刊：英文版 2011年第S3期21卷 670-674页

作者： ZHA Jian-feng1, 2. 3, GUO Guang-li1, 2. FENG Wen-kai3, WANG Qiang1, 2.1. key laboratory for Land Environment and {2. Monitoring of the state Bureau of Surveying and Mapping, china university of Mining and Technology, Xuzhou 2.1116, china 2. Jiangsu key laboratory of Resources and Environmental Information engineering, china university of Mining and Technology, Xuzhou 2.1116, china 3. state key laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu university of Technology, Chengdu 610059, china [a] key laboratory for Land Environment and {2. Monitoring of the state Bureau of Surveying and Mapping China University of Mining and Technology Xuzhou 221116 China [b] Jiangsu key laboratory of Resources and Environmental Information {2. China University of Mining and Technology Xuzhou 221116 China [c] state key {2. of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology Chengdu 610059 China

Solid backfilling mining can reduce the buildings' damage caused by mining greatly. The reduction of subsidence value, the slow advancing speed and the subsidence caused by backfilling body compaction are the main reasons that solid backfilling mining velocity decreases significantly. Based on the research of mechanism, some principles on subsidence control of solid backfilling mining under buildings were proposed. The equivalent mining height was designed according to the fortification criteria of buildings and their attachment structures, which enables the ground movement and deformation caused by mining to be less than the corresponding fortification criteria.

关键词： solid backfilling mining subsidence control mining under buildings

Thermal stabilization of chromium slag by sewage sludge: Effects of sludge quantity and temperature

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Journal of Environmental Sciences 2010年第7期22卷 1110-1115页

作者： Changlin Wu,Hua Zhang,Pinjing He,Liming Shao state key {2. of Pollution Control and Resources Reuse,key {2. of Yangtze River Water Environment,College of Environmental Science & engineering,tongji university,shanghai 200092,china. [a] state key {2. of Pollution Control Resources Reuse Key Laboratory of Yangtze River Water Environment College of Environmental Science & Engineering Tongji University Shanghai 200092 China. E-mail: solidwaste@***

To investigate the feasibility of detoxifying chromium slag by sewage sludge, synthetic chromium slag containing 3% of Cr（Ⅵ） was mixed with sewage sludge followed by thermal treatment in nitrogen gas for stabilizing chromium. The effects of slag to sludge ratio （0.5, 1 and 2. and temperature （2.0, 300, 500, 700 and 900℃） on treatment efficiency were investigated. During the mixing process before thermal treatment, 59.8%-99.7% of Cr（Ⅵ） was reduced, but Cr could be easily leached from the reduction product. Increasing heating temperature and decreasing slag to sludge ratio strengthened the reduction and stabilization of Cr（Ⅵ）. When the slag to sludge ratio was 0.5 and thermal treatment temperature was 300℃, the total leached Cr and Cr（Ⅵ） declined to 0.55 mg/L and 0.17 mg/L respectively, and 45.5% of Cr in the thermally treated residue existed as residual fraction. A two-stage mechanism was proposed for the reduction and stabilization of Cr.

关键词： chromium slag sewage sludge reduction detoxification thermal treatment leached concentration