Mapped relationships between pier settlement and rail deformation of bridges with CRTS III SBT

Lizhong Jiang,Lili Liu,Wangbao Zhou,Xiang Liu,Chao Liu,Ping Xiang 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.4

To study the rail mapped deformation caused by the pier settlement of simply - supported bridges with China Railway Track System Ⅲ (CRTS Ⅲ) slab ballastless track (SBT) system under the mode of non-longitudinal connection ballastless track slab, this study derived an analytical solution to the mapped relationships between pier settlement and rail deformation based on the interlayer interaction mechanism of rail-pier and principle of stationary potential energy. The analytical calculation results were compared with the numerical results obtained by ANSYS finite element calculation, thus verifying the accuracy of analytical method. A parameter analysis was conducted on the key factors in rail mapped deformation such as pier settlement, fastener stiffness, and self-compacting concrete (SCC) stiffness of filling layer. The results indicate that rail deformation is approximately proportional to pier settlement. The smaller the fastener stiffness, the smoother the rail deformation curve and the longer the rail deformation area is. With the increase in the stiffness of SCC filling layer, the maximum positive deformation of rail gradually decreases, and the maximum negative deformation gradually increases. The deformation of rail caused by the pier settlement of common-span bridge structures will generate low-frequency excitation on high-speed trains.

Distortional and local buckling of steel-concrete composite box-beam

Lizhong Jiang,Jingjing Qi,Andrew Scanlon,Linlin Sun 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.3

Distortional and local buckling are important factors that influences the bearing capacity of steel-concrete composite box-beam. Through theoretical analysis of distortional buckling forms, a stability analysis calculation model of composite box beam considering rotation of steel beam top flange is resented. The critical bending moment calculation formula of distortional buckling is established. In addition, mechanical behaviors of a steel beam web in the negative moment zone subjected separately to bending stress, shear stress and combined stress are investigated. Elastic buckling factors of steel web under different stress conditions are calculated. On the basis of local buckling analysis results, a limiting value for height-to thickness ratio of a steel web in the elastic stage is proposed. Numerical examples are presented to verify the proposed models.

Analysis on natural vibration characteristics of steel-concrete composite truss beam

Lizhong Jiang,Yulin Feng,Wangbao Zhou,Binbin He 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.1

In order to study the natural vibration characteristics of steel-concrete composite truss beam (SCCTB), the influence of multiple factors such as interface slip, shear deformation and moment of inertia are considered. Afterwards, based on the Hamilton principle the vibration control differential equation and natural boundary conditions of SCCTB are deduced. By solving SCCTB differential equations of vibration control, an analytical calculation method is proposed for analyzing the natural vibration characteristics of SCCTB. The natural frequencies of SCCTBs with different degrees of shear connection and effective lengths are calculated by using the analytical method, and the results are compared against those obtained from ANSYS finite element numerical calculation method. The results show that the analytical method considering the influence factors such as interface slip, shear deformation and moment of inertia are in good agreement with those obtained from ANSYS finite element numerical calculation method. This evidences the correctness of the analytical method and show that the method proposed exhibits improvement over the previously developed theories for the natural vibration characteristics of SCCTB. Finally, based on the analytical method, the influence factors of SCCTB natural vibration characteristics are analyzed. The results indicate that the influence of interface slip stiffness on SCCTB's natural frequency is more than 10% and therefore cannot be neglected. Moreover, shear deformation has an effect of more than 35% on SCCTB’s natural frequency and the effect cannot be ignored either in this case too.

Vibration characteristic analysis of high-speed railway simply supported beam bridge-track structure system

Lizhong Jiang,Yulin Feng,Wangbao Zhou,Binbin He 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.6

Based on the energy-variational principle, a coupling vibration analysis model of high-speed railway simply supported beam bridge-track structure system (HSRBTS) was established by considering the effect of shear deformation. The vibration differential equation and natural boundary conditions of HSRBTS were derived by considering the interlayer slip effect. Then, an analytic calculation method for the natural vibration frequency of this system was obtained. By taking two simply supported beam bridges of high-speed railway of 24 m and 32 m in span as examples, ANSYS and MIDAS finite-element numerical calculation methods were compared with the analytic method established in this paper. The calculation results show that two of them agree well with each other, validating the analytic method reported in this paper. The analytic method established in this study was used to evaluate the natural vibration characteristics of HSRBTS under different interlayer stiffness and length of rails at different subgrade sections. The results show that the vertical interlayer compressive stiffness had a great influence on the high-order natural vibration frequency of HSRBTS, and the effect of longitudinal interlayer slip stiffness on the natural vibration frequency of HSRBTS could be ignored. Under different vertical interlayer stiffness conditions, the subgrade section of HSRBTS has a critical rail length, and the critical length of rail at subgrade section decreases with the increase in vertical interlayer compressive stiffness.

Studies on restoring force model of concrete filled steel tubular laced column to composite box-beam connections

Lizhong Jiang,Zhi Huang,Wang-Bao Zhou,Shan Chen 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.6

Mega composite structure systems have been widely used in high rise buildings in China. Compared to other structures, this type of composite structure systems has a larger cross-section with less weight. Concrete filled steel tubular (CFST) laced column to box-beam connections are gaining popularity, in particular for the mega composite structure system in high rise buildings. To enable a better understanding of the destruction characteristics and aseismic performance of these connections, three different connection types of specimens including single-limb bracing, cross bracing and diaphragms for core area of connections were tested under low cyclic and reciprocating loading. Hysteresis curves and skeleton curves were obtained from cyclic loading tests under axial loading. Based on these tested curves, a new trilinear hysteretic restoring force model considering rigidity degradation is proposed for CFST laced column to box-beam connections in a mega composite structure system, including a trilinear skeleton model based on calculation, law of stiffness degradation and hysteresis rules. The trilinear hysteretic restoring force model is compared with the experimental results. The experimental data shows that the new hysteretic restoring force model tallies with the test curves well and can be referenced for elastic-plastic seismic analysis of CFST laced column to composite box-beam connection in a mega composite structure system.

Fundamental period estimation of steel frames equipped with steel panel walls

Liqiang Jiang,Xingshuo Zhang,Lizhong Jiang,Chang He,Jihong Ye,Yu Ran 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.6

Steel frames equipped with beam-only-connected steel panel wall (SPWF) system is one type of lateral resisting systems. The fundamental period is necessary to calculate the lateral force for seismic design, however, almost no investigations have been reported for the period estimation of SPWF structures, both in theoretically and in codes. This paper proposes a simple theoretical method to predict the fundamental periods of the SPWF structures based on the basic theory of engineering mechanics. The proposed method estimates the SPWF structures as a shear system of steel frames and a shear-flexure system of SPWs separately, and calculates the fundamental periods of the SPWF structures according to the integration of lateral stiffness of the steel frames and the SPWs along the height. Finite element method (FEM) is used to analyze the periods of 45 case steel frames or SPWF buildings with different configurations, and the FEM is validated by the test results of four specimens. The errors cannot be ignored between FEM and theoretical results due to the simplifications. Thus the finial formula is proposed by correcting the theoretical equations. The relative errors between the periods predicted from the final proposed formula and the results of FEM are no more than 4.6%. The proposed formula could be reliably used for fundamental period estimation of new, existing and damaged SPWF buildings.

A stochastic finite element method for dynamic analysis of bridge structures under moving loads

Xiang Liu,Lizhong Jiang,Ping Xiang,Zhipeng Lai,Yuntai Zhang,Lili Liu 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1

In structural engineering, the material properties of the structures such as elastic modulus, shear modulus, density, and size may not be deterministic and may vary at different locations. The dynamic response analysis of such structures may need to consider these properties as stochastic. This paper introduces a stochastic finite element method (SFEM) approach to analyze moving loads problems. Firstly, Karhunen-Loéve expansion (KLE) is applied for expressing the stochastic field of material properties. Then the mathematical expression of the random field is substituted into the finite element model to formulate the corresponding random matrix. Finally, the statistical moment of the dynamic response is calculated by the point estimation method (PEM). The accuracy and efficiency of the dynamic response obtained from the KLE-PEM are demonstrated by the example of a moving load passing through a simply supported Euler-Bernoulli beam, in which the material properties (including elastic modulus and density) are considered as random fields. The results from the KLE-PEM are compared with those from the Monte Carlo simulation. The results demonstrate that the proposed method of KLE-PEM has high accuracy and efficiency. By using the proposed SFEM, the random vertical deflection of a high-speed railway (HSR) bridge is analyzed by considering the random fields of material properties under the moving load of a train.

Influence of pier height on the effectiveness of seismic isolation of friction pendulum bearing for single-track railway bridges

Weikun He,Lizhong Jiang,Biao Wei,Zhenwei Wang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.2

Friction pendulum bearing (FPB) in bridges with different pier heights has various degrees of effectiveness of seismic isolation. To determine the applicability of FPB under different bridge pier height conditions, this paper focuses on the simply supported girder railway bridges that have three types of piers: solid piers with uniform cross-section, solid piers with non-uniform cross-section, and hollow piers with non-uniform cross-section. All of these bridges are first installed with FPB (isolation bearing) and later with non-isolation bearing, modeled by using OpenSEES finite element software. A shake table test is used to verify the related models. Based on nonlinear dynamic time history analysis, the seismic responses of isolated and non-isolated bridges are compared, and their corresponding seismic isolation ratios are calculated. Further, this paper introduces a fuzzy comprehensive evaluation method to determine the seismic isolation effect of FPB on bridges with different pier heights, by weighing and balancing the isolation ratios of different seismic responses of bridges. The results show that the transverse seismic isolation ratios of FPB are generally larger than the longitudinal seismic isolation ratios. In addition, FPB has poorer seismic isolation effect on tall piers compared with short piers.

Distortional Buckling Analysis of I-Steel Concrete Composite Beams Subjected to Hogging Moment

Lili Liu,Lizhong Jiang,Chun-dan Li,Wang-Bao Zhou,Lei-xin Nie 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3

Bending-torsional distortion buckling is one of the most critical buckling modes of steel–concrete composite beams when they are working under hogging moment. The rotational and lateral restraint stiff ness provided by the steel web to the steel bottom fl ange are the key factors to determine this form of buckling. Firstly, the formula for solving the elastic rotational restraint stiff ness of the composite fl ange of steel beam upper fl ange and concrete slab to the steel web is derived. Then, the equivalent lateral and rotational restraint stiff ness of the steel bottom fl ange subjected to hogging moment are thoroughly studied. Considering the rotation restraint eff ect of the composite fl ange, this paper provides the calculation formula for the critical bending moment of I-steel concrete composite beams (I-SCCB) under hogging moment. Fifteen examples are considered to calculate the critical bending moment of the I-SCCB under hogging moment with the simplifi ed analytical method introduced in this paper. The results are compared with the ones derived by ANSYS numerical analyses and relevant research of other scholars. The infl uence of the arrangement of the shear studs on the critical bending moment of the I-SCCB is investigated. It is concluded that the results given by the simplifi ed analytical method are in good agreement with the ones obtained by the ANSYS fi nite element numerical method. Both methods show that the critical load of the distortional buckling of the I-SCCB under hogging moment is less aff ected by the member’s length. The critical bending moment of distortional buckling of the I-SCCB signifi cantly increases with the presence of shear studs. However, once shear studs are used, it tends to be stable with the increase of equivalent restrained torsional rotational stiff ness at the top edge of the steel web.

Evaluation of optimal ground motion intensity measures of high-speed railway train running safety on bridges during earthquakes

Xiang Liu,Lizhong Jiang,Ping Xiang,Yulin Feng,Zhipeng Lai,Xiaoyun Sun 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.2

Due to the large number of railway bridges along China's high-speed railway (HSR) lines, which cover a wide area with many lines crossing the seismic zone, the possibility of a HSR train running over a bridge when an earthquake occurs is relatively high. Since the safety performance of the train will be threatened, it is necessary to study the safety of trains running over HSR bridges during earthquakes. However, ground motion (GM) is highly random and selecting the appropriate groundmotion intensity measures (IMs) for train running safety analysis is not trivial. To deal this problem, a model of a coupled trainbridge system under seismic excitation was established and 104 GM samples were selected to evaluate the correlation between 16 different IMs and train running safety over HSR bridges during earthquakes. The results show that spectral velocity (SvT1) and displacement (SdT1) at the fundamental period of the structure have good correlation with train running safety for mediumand long-period HSR bridges, and velocity spectrum intensity (VSI) and Housner intensity (HI) have good correlation for a wide range of structural periods. Overall, VSI and HI are the optimal IMs for safety analysis of trains running over HSR bridges during earthquakes. Finally, based on VSI and HI, the IM thresholds of an HSR bridge at different speed were analyzed.