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.

A harmonic movable tooth drive system integrated with shape memory alloys

Lizhong Xu,Zongxing Cai,Xiaodong He 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.4

Continuous rotating SMA actuators require motion conversion mechanisms, so their structure is relatively complex and difficult to realize the miniaturization. Here, a new type of continuous rotating actuator driven by SMA is proposed. It combines the movable tooth drive with SMA drive. The structure and working principle of the integrated movable tooth drive system is introduced. The equations of temperature, stress and strain of memory alloy wires, and the output torque of drive system are given. Using these equations, the temperature, the output forces of the SMA wires, and output torque of the drive system are studied. Results show that the compact drive system could give large output torque. To obtain large output torque plus small fluctuation, large eccentricity and small diameter of the SMA wire should be taken. Combined application of ventilation cooling and high current can increase the rotary speed of the drive system.

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.

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.

Reliability of mortar filling layer void length in in-service ballastless track-bridge system of HSR

Binbin He,Sheng Wen,Yulin Feng,Lizhong Jiang,Wangbao Zhou 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.1

To study the evaluation standard and control limit of mortar filling layer void length, in this paper, the train submodel was developed by MATLAB and the track-bridge sub-model considering the mortar filling layer void was established by ANSYS. The two sub-models were assembled into a train-track-bridge coupling dynamic model through the wheel-rail contact relationship, and the validity was corroborated by the coupling dynamic model with the literature model. Considering the randomness of fastening stiffness, mortar elastic modulus, length of mortar filling layer void, and pier settlement, the test points were designed by the Box-Behnken method based on Design-Expert software. The coupled dynamic model was calculated, and the support vector regression (SVR) nonlinear mapping model of the wheel-rail system was established. The learning, prediction, and verification were carried out. Finally, the reliable probability of the amplification coefficient distribution of the response index of the train and structure in different ranges was obtained based on the SVR nonlinear mapping model and Latin hypercube sampling method. The limit of the length of the mortar filling layer void was, thus, obtained. The results show that the SVR nonlinear mapping model developed in this paper has a high fitting accuracy of 0.993, and the computational efficiency is significantly improved by 99.86%. It can be used to calculate the dynamic response of the wheel-rail system. The length of the mortar filling layer void significantly affects the wheel-rail vertical force, wheel weight load reduction ratio, rail vertical displacement, and track plate vertical displacement. The dynamic response of the track structure has a more significant effect on the limit value of the length of the mortar filling layer void than the dynamic response of the vehicle, and the rail vertical displacement is the most obvious. At 250 km/h – 350 km/h train running speed, the limit values of grade Ⅰ, Ⅱ, and Ⅲ of the lengths of the mortar filling layer void are 3.932 m, 4.337 m, and 4.766 m, respectively. The results can provide some reference for the long-term service performance reliability of the ballastless track-bridge system of HRS.

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.

The impact of the convex friction distribution on the seismic response of a spring-friction isolation system

Biao Wei,Peng Wang,Xuhui He,Lizhong Jiang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

As for structures with rubber bearings during earthquakes, some firstly damaged bearings and the other normal bearings form atypical spring-friction isolation system. Furthermore, a rough contact surface, due to the stochastic damage of bearing, and the aroundsmooth contact surfaces form a convex distribution of friction coefficient. This paper attempts to analyze seismic responses of aspring-friction isolation system with a theoretically and linearly convex friction distribution, in which the friction coefficientgradually decreases with the distance from the center. The results show that such friction distribution inevitably increases thestructural relative displacement and possibly enlarges the structural acceleration and residual displacement under earthquakes. Theconvex pattern of friction distribution should be avoided in practical engineering, since it reduces the seismic isolation efficiency.

Hexadecylamine Modified Copper Nanowire Coated Superhydrophobic Cotton Fabric for Antifouling, Oil-water Separation, and Infrared Reflection Applications

Jiaojiao Zheng,Hong Zhang,Tianyu Cao,Yuanyuan Zhu,Lizhong He,Jianwei Li,Xudong Chen,Yinhu Qu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.10

Superhydrophobic surfaces by creating surface roughness followed by coating with low-surface-energyfluorinated materials have been intensively developed on cotton fabrics. However, exploring superhydrophobic surfaces withnon-fluorine components and further improving their attachment with cotton fabrics is still challenging. Herein, wedeveloped a superhydrophobic surface on cotton fabric by dip coating with hexadecylamine (HDA) modified coppernanowires (Cu NWs) based on the coordination between Cu atoms and amine groups. The HDA modified Cu NWs not onlycreated surface roughness, but also decreased the surface energy, leading to a superhydrophobic cotton fabric with watercontact angle of 164 °±2.0 °. Furthermore, ultrasonic washing and tape peeling tests exhibited the Cu NWs were adheredtightly to the surface of cotton fibers, owing to the strong hydrogen bond between amine groups on HDA molecules andhydroxyl groups on cotton fibers. In addition, the superhydrophobic cotton fabric showed excellent antifouling, oil-waterseparation and infrared reflection properties. It is believed that this facile method provide promising industrial applicationsfor fabricating superhydrophobic surfaces on other substrates.

Acteoside and Acyl-Migrated Acteoside, Compounds in Chinese Kudingcha Tea, Inhibit α-Amylase In Vitro

Yuqin Lu,Wenyu Zhou,Yue Feng,Yao Li,Ke Liu,Lizhong Liu,Dongxu Lin,Zhendan He,Xuli Wu 한국식품영양과학회 2017 Journal of medicinal food Vol.20 No.6

Acteoside, the predominant polyphenol of small-leaved kudingcha, the Chinese tea, has various biological activities. In this study, we examined the acyl migration of acteoside to isoacteoside with high-temperature treatment of acteoside. The inhibitory effects of acyl-migrated acteoside and acteoside on α-amylase were investigated, as were their binding interaction with α-amylase. The binding of acteoside and isoacteoside to α-amylase was investigated by using the fluorescence spectra assay, circular dichroism, and protein–ligand docking studies. Acteoside was more effective than preheated acteoside and isoacteoside in inhibiting α-amylase activity. Acteoside and isoacteoside binding to α-amylase may induce conformational changes to α-amylase, and the binding site of acteoside and isoacteoside being near the active site pocket of α-amylase may explain the decreased activity of α-amylase. The different affinities and binding sites of acteoside and isoacteoside for α-amylase resulted in different inhibition rates, which may be due to structural differences between acteoside and isoacteoside.