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A new isolation device using shape memory alloy and its application for long-span structures

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Earthquake Engineering and Engineering Vibration 2011年第2期10卷 239-252页

作者： ding youliang Chen Xin Li Aiqun Zuo Xiaobao Key Laboratory of Concrete and Prestressed Concrete Structure of Ministry of Education Southeast University Nanjing 210096 China Department of Civil Engineering Nanjing University of Science ＆ Technology Nanjing 210094 China

The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys （SMA） are the constitutive model, the SMA isolation device and the analysis method. In this paper, a simplified constitutive model based on the classic theory of plasticity is proposed to simulate the behavior of the superelasticity of the SMA, in which the martensite volume fraction is considered as one of the state variables. Comparisons between simulation results and experimental results are made and indicate that the proposed constitutive model yields stress-strain curves that are in good agreement with the experimental ones. Thus, the proposed model can correctly simulate the yield mechanism and energy dissipation capacity of the SMA. Next, in order to make full use of the superelasticity of SMA, a new SMA isolator composed of pre-tensioned SMA bars is presented. Then, a finite element analytical model is established to simulate the behavior of the SMA isolator according to its configuration and simplified constitutive model. Finally, a simplified design method for long-span structures installed with SMA isolators is proposed, which is further used to investigate the isolation effects of a space grid structure. Results show that the SMA isolator can reduce the seismic responses of the structure effectively, which indicates the effectiveness of the proposed SMA isolation method.

关键词： shape memory alloy super-elasticity constitutive model seismic response structural isolation space gridstructure

Environmental variability study on the measured responses of Runyang Cablestayed Bridge using wavelet packet analysis

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Science China(Technological Sciences) 2008年第5期51卷 517-528页

作者： ding youliang LI AiQun LIU Tao College of Civil Engineering Southeast UniversityNanjing 210096China

The structural damage alarming method based on wavelet packet energy spectrum (WPES) for long-span cable-stayed bridges is presented through combination of ambient vibration test and wavelet packet analysis. The environmental variability in the measured WPES and damage alarming indices ERVD of the Runyang Cable-stayed Bridge are discussed in detail using the wavelet packet analysis of the measured acceleration responses of the bridge under daily environmental conditions. The analysis results reveal that the actual environmental conditions including traffic loadings, environmental temperature and typhoon loadings have remarkable correlations with the measured WPES. The changes of environmental temperature have a long-term trend influence on the WPES, while the influences of traffic and typhoon loadings on the measured WPES of the bridge present instantaneous changes because of the nonstationary properties of the loadings. The analysis results of the measured responses further reveal that the damage alarming indices ERVD can sensitively reflect the influences of environmental temperature and typhoon loadings on the dynamic properties of Runyang Cable-stayed Bridge. Therefore, the proposed structural damage alarming indices ERVD under ambient vibrations are suitable for real-time damage alarming for long-span cable-stayed bridges.

关键词： cable-stayed bridge wavelet packet analysis wavelet packet energy spectrum ambient vibration structural damage alarming

Research on seasonal correlation of wavelet packet energy spectrum and temperature of Runyang Suspension Bridge

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Science China(Technological Sciences) 2009年第6期52卷 1776-1785页

作者： youliang ding AiQun Li Jun Sun Yang Deng School of Civil Engineering Southeast University Nanjing 210096 China

In order to establish an environmental-condition-normalized structural damage alarming method, the seasonal correlation analysis of wavelet packet energy spectrum (WPES) and temperature of Runyang Suspension Bridge is performed by means of the 236-day health monitoring data. The analysis results reveal that the measured WPES has remarkable seasonal correlation with the environmental temperature. The seasonal change of environmental temperature accounts for the variation of the damage alarming parameter I p of the dominant frequency bands with an averaged variance of 200%. The statistical modeling technique using a 6th-order polynomial is adopted to formulate the correlation between the WPES and temperature, on the basis of which the abnormal changes of measured damage alarming parameter I p are detected using the mean value control chart. It is found that the proposed method can effectively eliminate temperature complications from the time series of WPES and exhibit good capability for detecting the damage-induced 10% variances of the damage alarming parameter I p . And the proposed WPES-based method is superior the modal frequency and hence is more suitable for online real-time damage alarming for long-span bridges.

关键词： structural damage alarming wavelet packet energy spectrum wavelet packet analysis temperature seasonal correlation suspension bridge

Fatigue reliability assessment for bridge welded details using long-term monitoring data

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Science China(Technological Sciences) 2011年第12期54卷 3371-3381页

作者： DENG Yang ding youliang LI AiQun ZHOU GuangDong Key Laboratory of Concrete and Prestressed Concrete Structure of Ministry of Education Southeast University Nanjing 210096 China

A reliability assessment method of fatigue life based on the long-term monitoring data is developed for welded details in steel box girder,and the application research is presented with examples of welded rib-to-deck details in Runyang Bridges. Firstly the fatigue damage limit-state function is established based on S-N curves and Miner's rule,and the probability distribution characteristics of the coefficients in the function are discussed in detail. The uncertainties in fatigue loading effects are mainly studied based on long-term monitoring data. In the traditional studies,only the uncertainty of equivalent stress range is considered in fatigue reliability assessment. However,stress cycle number is also treated as a random variable in this paper because we know traffic flow every day differs in a thousand ways. Then the optimization method is employed to calculate the fatigue reliability. After studying the changing law of the reliability indices with time and the effect of the randomness of stress cycle number on reliability,the effect of the traffic growth on the reliability is studied. This study shows that the uncertainty in the fatigue life of the welded details can be well studied based on structural health monitoring,so it is necessary to carry out long-term strain monitoring of the welded details for accurate fatigue reliability assessment during the whole service period.

关键词： steel box girder fatigue loading effects equivalent stress range stress cycle number fatigue reliability traffic growth

Analysis and assessment of bridge health monitoring mass data——progress in research/development of “Structural Health Monitoring”

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Science China(Technological Sciences) 2012年第8期55卷 2212-2224页

作者： LI AiQun ding youliang WANG Hao GUO Tong Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast UniversityNanjing 210096China

The "Structural Health Monitoring" is a project supported by National Natural Science Foundation for Distinguished Young Scholars of China(Grant No.50725828).To meet the urgent requirements of analysis and assessment of mass monitoring data of bridge environmental actions and structural responses,the monitoring of environmental actions and action effect modeling methods,dynamic performance monitoring and early warning methods,condition assessment and operation maintenance methods of key members are systematically studied in close combination with structural characteristics of long-span cable-stayed bridges and suspension *** paper reports the progress of the project as follows.(1) The environmental action modeling methods of long-span bridges are established based on monitoring data of temperature,sustained wind and *** action effect modeling methods are further developed in combination with the multi-scale baseline finite element modeling method for long-span bridges.(2) The identification methods of global dynamic characteristics and internal forces of cables and hangers for long-span cable-stayed bridges and suspension bridges are proposed using the vibration monitoring data,on the basis of which the condition monitoring and early warning methods of bridges are developed using the environmental-condition-normalization technique.(3) The analysis methods for fatigue loading effect of welded details of steel box girder,temperature and traffic loading effect of expansion joint are presented based on long-term monitoring data of strain and beam-end displacement,on the basis of which the service performance assessment and remaining life prediction methods are developed.

关键词： structural health monitoring bridge mass data condition assessment environmental action

Investigations on serviceability control of long-span structures under human-induced excitation

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Earthquake Engineering and Engineering Vibration 2012年第1期11卷 57-71页

作者： Chen Xin ding youliang Li Ai-qun Zhang Zhiqiang Sun Peng Key Laboratory of Concrete and Prestressed Concrete Structure of Ministry of Education Southeast University Nanjing 210096 China School of Civil Engineering Suzhou University of Science and Technology Suzhou 215011 China

The increasing strength of new structural materials and the span of new structures, accompanied by aesthetic requirements for greater slenderness, are resulting in more applications of long-span structures. In this paper, serviceability control technology and its design theory are studied. First, a novel tuned mass damper （TMD） with controllable stiffness is developed. Second, methods for modeling human-induced loads are proposed, including standing up, walking, jumping and running, and an analysis method for long-span floor response is proposed based on a finite element model. Third, a design method for long-span floors installed with a multiple TMD （MTMD） system considering human comfort is introduced, largely based on a study of existing literature. Finally, a design, analysis and field test is conducted using several large scale buildings in China including the Beijing Olympic Park National Conference Center, Changsha New Railway Station and the Xi＇an Northern Railway Station. The analytical and field test results show that the MTMD system designed using the proposed method is capable of effectively mitigating the vertical vibration of long-span floor structures. The study presented in this paper provides an important reference for the analysis of vibration serviceability of similar long-span floors and design of control system for these structures.

关键词： long-span floor vibration control TMD human-inducing loads vibration serviceability

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental conditions

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Frontiers of Structural and Civil Engineering 2011年第3期5卷 374-380页

作者： youliang ding Aiqun LI School of Civil Engineering Southeast UniversityNanjing 210096China

This paper addresses the problem of condition assessment of bridge expansion joints using long-term measurement data under changing environmental *** effects of temperature,traffic loading and wind on the expansion joint displacements are analyzed and interpreted,which reveal that measured displacements are observed to increase with an increase in temperature and to decrease with increased traffic loading,while the correlation between displacement and wind speed is very *** regression models are developed to simulate the varying displacements under the changes in temperature and traffic *** on these models,the effects of the environmental conditions are removed to obtain the normalized *** process control using mean value control charts is further used to detect damage to the bridge expansion *** results reveal that the proposed method had a good capability for detecting the damage-induced 1.0%variances of the annual changes in the expansion joint displacements.

关键词： structural health monitoring displacement expansion joint temperature effect wind effect traffic loading statistical process control suspension bridge

Fatigue Performance of Orthotropic Steel Decks in Super-Wide Steel Box Girder Considering Transverse Distribution of Vehicle Load

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Structural Durability & Health Monitoring 2021年第4期15卷 299-316页

作者： Xudong Wang Changqing Miao Mao Yang youliang ding Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast UniversityNanjing211189China School of Civil Engineering Southeast UniversityNanjing211189China

This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis *** stress behavior of super-wide steel box girders under the vehicle load at different lane locations is ***,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage *** results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to *** fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.

关键词： Orthotropic steel deck steel box girder fatigue life vehicle transverse distribution model finite element analysis

A new look at the response surface method for reliability analysis using chaos theory

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Earthquake Engineering and Engineering Vibration 2008年第3期7卷 329-335页

作者： ding youliang, Li Aiqun and Deng Yang College of Civil Engineering, Southeast University, Nanjing 210096, China Lecturer Professor PhD Student College of Civil Engineering Southeast University Nanjing 210096 China

To overcome excessive computation errors and convergence failures encountered in an iterative calculation of the reliability index using the response surface method （RSM） for some nonlinear limit state functions, this study investigates an essential factor based on chaotic dynamics theory. The bifurcation diagrams of the reliability index are presented for some typical nonlinear limit state functions, and the computation results from the mapping functions due to the RSM iterations show the complicated dynamic phenomena such as the periodic oscillation, as well as bifurcation and chaos. From the numerical examples, it is concluded that the parameter of selection range fplays an important role in the convergence of the RSM iteration, and an improved RSM iterative algorithm is proposed with regard to the incorporation of the iterative sequential function of selection rangef The proposed method is shown to be efficient and to yield accurate results.

关键词： structural reliability response surface method chaotic dynamics convergence failure selection range nonlinearity