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Numerical simulation of the seismic behavior of self-centering steel beam-column connections with bottom flange friction devices

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Earthquake Engineering and Engineering Vibration 2011年第2期10卷 229-238页

作者： Guo Tong Song Lianglong Zhang Guodong Key Laboratory of concrete and Prestressed concrete Structure Ministry of Education Southeast Univ. Nanjing 210096 China

A new type of steel moment resisting frame with bottom flange friction devices （BFFDs） has been developed to provide self-centering capacity and energy dissipation, and to reduce permanent deformations under earthquakes. This paper presents a numerical simulation of self-centering beam-column connections with BFFDs, in which the gap opening/closing at the beam-column interfaces is simulated by using pairs of zero-length elements with compression-only material properties, and the energy dissipation due to friction is simulated by using truss elements with specified hysteretic behavior. In particular, the effect of the friction bolt bearing against the slotted plate in the BFFDs was modeled, so that the increase in lateral force and the loss of friction force due to the bolt bearing could be taken into account. Parallel elastic-perfectly plastic gap （ElasticPPGap） materials in the Open System for Earthquake Engineering Simulation （OpenSees） were used with predefined gaps to specify the sequence that each bolt went into the bearing and the corresponding increase in bending stiffness. The MinMax material in OpenSees is used to specify the minimum and maximum values of strains of the ElasticPPGap materials. To consider the loss of friction force due to bok bearing, a number of parallel hysteretic materials were used, and the failure of these materials in sequence simulated the gradual loss of friction force. Analysis results obtained by using the proposed numerical model are discussed and compared with the test results under cyclic loadings and the seismic loading, respectively.

关键词： numerical simulation post tensioned self-centering moment resisting steel frame bottom flange frictiondevice bolt bearing

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Research on failure scenarios of domes based on form vulnerability

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Science China(Technological Sciences) 2011年第11期54卷 2834-2853页

作者： YE JiHong LIU WenZheng PAN Rui Key Laboratory of concrete and Prestressed concrete Structures of Ministry of Education Southeast University Nanjing 210018 China

In this paper, form vulnerability theory was applied to the analysis of the failure mechanisms of single-layer latticed spherical shells subjected to seismic excitations. Three 1/10 scale testing models were designed with characteristics as follows： Model 1 possesses overall uniform stiffness and is expected to collapse in the strength failure mode as some members become plastic; Model 2 possesses six man-made weak parts located on six radial main rib zones and is expected to collapse in the dynamic in- stability mode with all members still in the elastic stage; Model 3 strengthens the six weak zones of Model 2, and therefore, its stiffness is uniform. Model 3 is proposed to collapse in the strength failure mode when the members are still in the elastic stage By increasing the peak ground accelerations of seismic waves gradually, the shaking table tests were carried out until all three models collapsed （or locally collapsed）. On the basis of form vulnerability theory, topological hierarchy models of the test models were established through a clustering process, and various failure scenarios, including overall collapse scenarios and partial collapse scenarios, were identified by unzipping corresponding hierarchical models. By comparison of the failure scenarios based on theoretical analysis and experiments, it was found that vulnerability theory could effectively reflect the weak- ness zones in topological relations of the structures from the perspective of internal causes. The intemal mechanisms of the distinct failure characteristics of reticulated shells subjected to seismic excitations were also revealed in this process. The well-formedness of structural clusters, Q, is closely related to the collapse modes, i.e., uniform changes of Q indicate a uniform distribution of overall structural stiffness, which indicates that strength failure is likely to happen; conversely, non-uniform changes of Q indicate that weak zones exist in the structure, and dynamic instabilit

关键词： single-layer latticed spherical shell form vulnerabifity collapse mode failure mechanism shaking table test

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Study on Thermal Insulation Performance of Cross-Laminated Bamboo Wall

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Journal of Renewable Materials 2019年第11期7卷 1231-1250页

作者： Qingfang Lv Weiyang Wang Ye Liu Key Laboratory of concrete and Prestressed concrete Structures of the Ministry of Education Southeast UniversityNanjing210096China

In recent years,bamboo,as a green building material,has attracted more and more attention *** by the investigation of cross-laminated timber in structural systems,a new engineered cross-laminated bamboo(CLB)consisting of the cross lamination of bamboo scrimber plates is proposed in this *** evaluate its potential in structural applications,the thermal insulation performances of the CLB walls and CLB walls with the EPS foam plate were studied and evaluated by the temperature-controlled box-heat flow meter *** results indicated that the thermal insulation performance improved with the increase of thickness,but different wall configurations had little effect on the thermal insulation performance under the same thickness of the CLB *** thermal insulation performance of EPS-CLB composite wall was much better than that of CLB *** addition,a relatively acceptable accuracy of the theoretical calculations was ***,the influence of different locations of the EPS foam plate on heat transfer coefficient can be neglected as it was studied based on the validated numerical models.

关键词： Cross-laminated bamboo steady-state heat transfer guarded hot plate method temperature-controlled box-heat flow meter method thermal insulation performance

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Study on correlations of modal frequencies and environmental factors for a suspension bridge based on improved neural networks

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Science China(Technological Sciences) 2010年第9期53卷 2501-2509页

作者： DING YouLiang,DENG Yang & LI AiQun Key Laboratory of concrete and Prestressed concrete Structure of Ministry of Education,Southeast University,Nanjing 210096,China Key Laboratory of concrete and Prestressed concrete Structure of Ministry of Education Southeast University Nanjing China

By using of long-term monitoring data of Runyang Suspension Bridge,the improved back-propagation neural networks (BPNNs) are formulated for modeling the correlations between modal frequencies and environmental conditions including wind,temperature and vehicle ***,with the correlation models the environmental effects on modal frequencies are quantified and the abnormal changes of measured frequencies are detected by means of the hypothesis *** results reveal that BPNN-based correlation models improved by both early stopping and Bayesian regularization techniques exhibit excellent generalization *** the developed correlation models can effectively reduce the environmental variability in modal *** t-test method provides a good capability to detect the damage-induced 0.16% and 0.12% abnormal changes of the 5th and 6th modal frequencies,***,the proposed method is suitable for real-time monitoring of suspension bridge conditions.

关键词： modal frequency environmental condition correlation artificial neural networks hypothesis test suspension bridge

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Analysis of actuator delay and its effect on uncertainty quantification for real-time hybrid simulation

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Earthquake Engineering and Engineering Vibration 2017年第4期16卷 713-725页

作者： Cheng Chen Weijie Xu Tong Guo Kai Chen School of Engineering San Francisco State University Key Laboratory of concrete and Prestressed concrete Structures of the Ministry of Education Southeast University

Uncertainties in structure properties can result in different responses in hybrid simulations. Quantification of the effect of these tmcertainties would enable researchers to estimate the variances of structural responses observed from experiments. This poses challenges for real-time hybrid simulation （RTHS） due to the existence of actuator delay. Polynomial chaos expansion （PCE） projects the model outputs on a basis of orthogonal stochastic polynomials to account for influences of model uncertainties. In this paper, PCE is utilized to evaluate effect of actuator delay on the maximum displacement from real-time hybrid simulation of a single degree of freedom （SDOF） structure when accounting for uncertainties in structural properties. The PCE is first applied for RTHS without delay to determine the order of PCE, the number of sample points as well as the method for coefficients calculation. The PCE is then applied to RTHS with actuator delay. The mean, variance and Sobol indices are compared and discussed to evaluate the effects of actuator delay on uncertainty quantification for RTHS. Results show that the mean and the variance of the maximum displacement increase linearly and exponentially with respect to actuator delay, respectively. Sensitivity analysis through Sobol indices also indicates the influence of the single random variable decreases while the coupling effect increases with the increase of actuator delay.

关键词： real-time hybrid simulation actuator delay polynomial chaos expansion delay differential equation uncertainty quantification

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Numerical simulation of non-Gaussian wind load

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Science China(Technological Sciences) 2012年第11期55卷 3057-3069页

作者： YE JiHong DING JingHu LIU ChuanYan Key Laboratory of concrete and Prestressed concrete Structures of Ministry of Education Southeast UniversityNanjing 210018China

Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.

关键词： non-Gaussian wind load power spectrum skewness kurtosis numerical simulation

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Analytical and experimental study on mild steel dampers with non-uniform vertical slits

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Earthquake Engineering and Engineering Vibration 2015年第1期14卷 111-123页

作者： Zheng Jie Li Aiqun Guo Tong School of Civil Engineering Southeast University Key Laboratory of concrete and Prestressed concrete Structure of China Ministry of Education Southeast University

This study proposes a novel mild steel damper with non-uniform vertical slits. The influence of different shapes of vertical slits of the core energy plate on the energy dissipation and buckling resistance capacities is analyzed. Based on the theoretical analysis, formulas of key parameters of the dampers, including the elastic lateral stiffness, shear bearing capacity and yield displacement, are derived. The effectiveness of the proposed damper is demonstrated through pseudo static tests on four 0.25-scale specimens. Performance of these dampers, i.e. cyclic deformation, stress distribution, energy dissipation capacity, etc., are presented and discussed. Using the numerical models of dampers calibrated through test data, earthquake time-history analyses were conducted, and it is observed that the dampers significantly reduce the seismic responses of the prototype frame and have a desirable energy dissipation capacity.

关键词： mild steel damper vertical slit pseudo static test energy dissipation

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Study on seismic response control of a single-tower self-anchored suspension bridge with elastic-plastic steel damper

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Science China(Technological Sciences) 2012年第6期55卷 1496-1502页

作者： WANG Hao ZHOU Rui ZONG ZhouHong WANG Chen LI AiQun Key Laboratory of concrete&Prestressed concrete Structure of Ministry of Education Southeast UniversityNanjing 210096China

Elastic-plastic steel damper(EPSD) is a new device controlling seismic *** mechanical principle of EPSD was presented and a comparison was conducted between the theoretical formulas and finite element(FE) simulation of damper *** verified force-displacement hysteretic curve of the damper system was obtained with reference to *** Nanjing Jiangxinzhou Bridge(NJB) was subsequently taken as the case to investigate the seismic response control effect of EPSDs on single-tower self-anchored suspension bridges.A 3-dimensional FE model of the bridge was established in ANSYS and the dynamic and static analyses of the bridge were conducted,the control effect of EPSDs under different seismic waves was further investigated through nonlinear time-history analysis based on the validated *** showed that both the simplified theoretical and FE simulation methods can preferable reflect the mechanical performance of EPSD,and that seismic responses of NJB with EPSDs are better than those with elastic connection device or fluid viscous ***,the control effect of EPSDs is influenced by seismic wave characteristics.

关键词： elastic-plastic steel damper single-tower self-anchored suspension bridge FE model validation nonlinear time-historyanalysis seismic response control

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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

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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

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