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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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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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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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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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Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

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Journal of Central South University 2015年第4期22卷 1536-1547页

作者：孙建邱洪兴 key laboratory of concrete and prestressed concrete structures of ministry of education (Southeast University)

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

关键词： precast shear wall vertical joint seismic behavior high-strength bolt connecting steel frame

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Theoretical modeling of steel reinforced ECC column under eccentric compressive loading

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Science china(Technological Sciences) 2015年第5期58卷 889-898页

作者： PAN JinLong GU Jie CHEN JunHan key laboratory of concrete and prestressed concrete structures of ministry of education Southeast University

Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.

关键词： compressive reinforced ultimate durability constitutive reinforcement tensile columns carrying calculating

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Structural condition assessment of long-span suspension bridges using long-term monitoring data

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Earthquake Engineering and Engineering Vibration 2010年第1期9卷 123-131页

作者： Deng Yang~+,Ding Youliang~(++) and Li Aiqun~§key laboratory of concrete & prestressed concrete structures of ministry of education,Southeast University,Nanjing 210096,china PhD Student ++ Assistant Professor ~§Professor key laboratory of concrete & prestressed concrete structures of ministry of education Southeast University Nanjing China

This paper focuses on developing an online structural condition assessment technique using long-term monitoring data measured by a structural health monitoring system. The seasonal correlations of frequency-temperature and beam-end displacement-temperature for the Runyang Suspension Bridge are performed, first. Then, a statistical modeling technique using a six-order polynomial is further applied to formulate the correlations of frequency-temperature and displacement-temperature, from which abnormal changes of measured frequencies and displacements are detected using the mean value control chart. Analysis results show that modal frequencies of higher vibration modes and displacements have remarkable seasonal correlations with the environmental temperature and the proposed method exhibits a good capability for detecting the micro damage-induced changes of modal frequencies and displacements. The results demonstrate that the proposed method can effectively eliminate temperature complications from frequency and displacement time series and is well suited for online condition monitoring of long-span suspension bridges.

关键词： structural health monitoring modal frequency beam-end displacement temperature seasonal correlation suspension bridge

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Seismic stability of earth slopes with tension crack

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Frontiers of Structural and Civil Engineering 2019年第4期13卷 950-964页

作者： Yundong ZHOU Fei ZHANG Jingquan Wang Yufeng GAO Guangyu DAI key laboratory of ministry of education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China key laboratory of concrete and prestressed concrete structure of china ministry of education Southeast UniversityNanjing 211189China

Cracks at the crest of slopes frequently occur during earthquakes. Such cracks result from limited tension strength of the soil. A tension cut-off in Mohr-Coulomb shear strength can represent this limited strength. Presented is an extension of variational analysis of slope stability with a tension crack considering seismicity. Both translational and rotational failure mechanisms are included in a pseudo-static analysis of slope stability. Developed is a closed-form to assess the seismic stability of slopes with zero tensile strength. The results indicate that the presence of the tension crack has significant effects on the seismic stability of slopes, i.e., leading to small value of the yield acceleration. Considering soil tension strength in seismic slope analysis may lead to overestimation on the stability, as much as 50% for vertical slopes. Imposing tension crack results in transit of the critical failure mode to a straight line from a log-spiral, except for flat slopes with small soil cohesion. Under seismic conditions, large cohesion may increase the depth of crack, moving it closer to the slope.

关键词： slope stability tension crack limit equilibrium seismic effect

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Compressive performance of a foam-filled fiber-reinforced grid beetle elytron plate

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Science china(Technological Sciences) 2023年第3期66卷 830-840页

作者： HAO Ning SONG YiHeng CHEN JinXiang HE ChaoChao LI YinSheng key laboratory of concrete and prestressed concrete structures of the ministry of education Southeast UniversityNanjing 211189China

The compressive mechanical properties,failure modes and foam filler strengthening mechanism and effect of a short basalt fiber-reinforced epoxy resin composite grid beetle elytron plate with a polyvinyl chloride(PVC)foam-filled core(GBEPfc)are investigated via compression experiments and the finite element *** results are compared with those of a grid plate(GPfc)with the same wall thickness as the ***,a fully integrated preparation method and process are developed for the GBEPfc,with a material composition that is close to the structure and composition of the *** of more than 20%in the specific compressive strength and specific energy absorption of the GBEPfcrelative to the GPfcare *** foam provides a constraining force for the fiber composite structure;consequently,the trabeculae and honeycomb walls of the core transition from a lower-order deformation that easily occurs to a higher-order deformation that occurs less *** interaction between the core composite structure and PVC foam is *** GBEPfcdeveloped in this paper is simple in structure and easy to prepare,and the material composition is close to biological prototypes and materials used in practical engineerings,which lays a foundation for the application of beetle elytron plates.

关键词： beetle elytron beetle elytron plate foam-filled sandwich plate basalt fiber-reinforced polymer(BFRP) compressive properties

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