Comparable study on typhoon and strong northern wind characteristics of the Runyang Suspension Bridge based on field tests

The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measurement data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS）of the RSB and field tests during strong winds. The differences between the typhoon and the strong northern wind are especially studied. It is found that the mean wind speed of the strong northern wind is a little smaller and the mean wind direction is more stable than that of the typhoon. The turbulence intensity of both the typhoon and the strong northern wind is greater than the values suggested in Chinese code, and the turbulence integral length difference between the typhoon and a strong northern wind is not clear. As for the along-wind turbulence power spectrum, the spectrum of the strong northern wind can fit the Kaimal spectrum better than that of the typhoon. The obtained results can provide measurement data for founding a strong wind characteristic database and determining the strong wind characteristic parameter values of the RSB.

Dynamic characteristics of conveyor belts

The dynamic characteristics of a belt conveyor are determined to a large extent by the properties of the belt. This paper describes experiments designed to establish the dynamic properties of belting material. The dynamic elastic modulus, viscous damping and rheologicat constants of the belt were measured. Several properties were studied as a function of the tensile loading on the belt. These included longitudinal vibration, the natural vibration frequency in the transverse direction and the response to an impulse excitation. Vibration response was observed under several different excitation frequencies. Most of these properties have not been tested previously under conditions appropriate for the ISO/DP9856 standard. Two types of belt were tested, a steel reinforced belt and a fabric reinforced belt. The test equipment was built to provide data appropriate for designing belt conveyors. It was observed that the stress wave propagation speed increased with tensile load and that tensile load was the main factor influencing longitudinal vibrations.

The influence of charge characteristics of suspension droplets on the ion flow field in different temperatures and humidity

In order to clarify the charging characteristics of suspension droplets in ion flow field under different temperatures and humidity,the effective charging factor used to characterize the charging characteristics of suspension droplets is introduced in this paper,and a calculation method of charging factor is proposed based on the upstream finite element method(FEM).Then,the charging factor under different temperatures and humidity is calculated,and the analytic expression of the charging factor considering the influence of temperature and humidity is obtained by fitting the calculation results.The influence of suspension droplets on the ion flow field is analyzed.The results show that the charging factor is small and increases little with the relative humidity when the relative humidity is less than 60%,and the charging factor is large and increases rapidly with the relative humidity when the relative humidity is more than 60%.At the same relative humidity,the charging factor increases linearly with the temperature.The influence of charged suspension droplets on the ion flow field can be ignored when the relative humidity is less than 60%and must be considered under high temperature and humidity.The calculation method and analytic expression of the charging factor proposed in this paper can be used to model of ion flow field considering the influence of temperature and humidity and provide technical support for the construction of HVDC transmission lines across high temperature and humidity.

Research on dynamic characteristics model test scheme for middle pylon of multi-pylon multi-span suspension bridges

Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal rigidity, the structural form and the corresponding foundation type of middle pylon are different from those of the ordinary steel pylon, and the complicated dynamic characteristics make the calculation quite difficult. In this article, exploration has been made in selection of similarity ratio and model materials, section simulation, restriction conditions simulation, fixing of mass blocks, fabrication scheme and testing method by taking into account different construction and working conditions such as restriction conditions and working environment of a three-pylon suspension bridge, to conduct the test experimental design of the dynamic behavior of the middle pylon, with the purpose to reveal its dynamic characteristics and make comparison and analysis with theoretical assumptions, to provide basis for anti-wind and anti-seismic design and reference for the design and research of three-pylon two-span suspension bridges in the future.

Research on Vibration Characteristics of Large Scale Belt Conveyor and Its Application

High speed and large capacity belt conveyor is the main development trend. In the design, calculated and used of belt conveyor must be considered the high speed, large capacity, dynamic load. This paper starts from the analysis of conveyor belt transverse vibration. Through calculate transverse vibration natural frequency of conveyor belt, and analyze the lateral stability of belt conveyor.

Dynamic Characteristics of Long -Span Steel -Concrete CompositeBeam Bridge Based on Vehicle -Bridge Coupling Effect

In order to investigate the effect of vehicle-bridge coupling on the dynamic characteristics of the bridge,a steel-concrete composite beam suspension bridge is taken as the research object,and a three-dimensional spatial model of the bridge and a biaxial vehicle model of the vehicle are established,and then a vehicle-bridge coupling vibration system is constructed on the basis of the Nemak-βmethod,and the impact coefficients of each part of the bridge are obtained under different bridge deck unevenness and vehicle speed.The simulation results show that the bridge deck unevenness has the greatest influence on the vibration response of the bridge,and the bridge impact coefficient increases along with the increase in the level of bridge deck unevenness,and the impact coefficient of the main longitudinal girder and the secondary longitudinal girder achieves the maximum value when the level 4 unevenness is 0.328 and 0.314,respectively;when the vehicle speed is increased,the vibration response of the bridge increases and then decreases,and the impact coefficient of the bridge in the middle of the bridge at a speed of 60 km/h achieves the maximum value of 0.192.

Influence of central buckle on suspension bridge dynamic characteristics and driving comfort

The central buckle, which is often used in a suspension bridge, can improve bridges' performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and bridge-deck driving comfort of a long-span suspension bridge is studied by using a case study of Siduhe Suspension Bridge in China. Based on the finite element software ANSYS and independently complied program, the influence of the central buckle on the structure force-applied characteristics of a long-span suspension bridge has been explored. The results show that the huge increases of natural frequencies can result in the presence of central buckles because of the increases of bending and torsional rigidities. The central buckle basically makes the stiffening girders and cables within the triangular area covered as a relatively approximate rigid area. Hence, the central buckle can reduce the torsional displacement of the main girder. However, the increases of bending and torsional rigidities have little influence on the impact factor, which is obtained by using vehicle-bridge coupled vibration analysis. This means that the central buckle has little effect on the comfort indices. In addition, it is found that the central buckle can enhance the bridge deck's driving stability due to the decrease of the torsional displacements of the main girder.

GENERATION OF ASYMMETRIC F-v CHARACTERISTICS FOR SYMMETRIC MR DAMPERS

An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological （MR） dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the “on-off” control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.

Study on effects of environmental temperature on dynamic characteristics of Taizhou Yangtze River Bridge

The dynamic characteristics of three-tower and two-span suspension bridge are analyzed at different global temperatures. An equivalent cable inner force method is proposed to consider temperature effects and to study the effects of environmental temperature on dynamic characteristics of Taizhou Yangtze River Bridge. The result demonstrates that the effects of temperature can not be neglected in static or dynamic analysis of Taizhou Yangtze River Bridge. The relationship between temperature and frequency is negative. The effects of temperature should be taken into account in experimental modal analysis of long-span bridges and damage identification.

Parameter effects on the dynamic characteristics of a super-long-span triple-tower suspension bridge

A 3D finite element model for the Taizhou Yangtze River Bridge,the first triple-tower long-span suspension bridge in China,is established based on the nonlinear finite element software ABAQUS,and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical,lateral and torsional stiffness of the steel box girder,the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that,in general,the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical,lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic re-straints have a more significant effect on the dynamic characteristics than the central buckle,and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also,rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.

Self-centering characteristics of a petal-shaped capsule robot

Based on the multiple wedge effects, a petal-shaped capsule robot(PCR) is proposed, and the self-centering phenomenon of the PCR is discovered. For investigating the self-centering characteristics, an innovative concept of the instantaneous fluid membrane(FM) thickness, along with the dynamic FM thickness, is proposed; thus a dynamic FM thickness model and a hydrodynamic pressure(HP) model are derived when the PCR axis deviates from the pipe axis under the effect of gravity. A kinematics equation during suspending process in the vertical direction and a swimming kinematics equation in axial direction are derived respectively. Four capsule robots with different eccentricities of the tiles were manufactured and tested, the theoretical and experimental results show that the HP gradient is a fundamental reason for the self-centering phenomenon. The PCR with the self-centering ability can directly avoid the contact with the bottom of the gastrointestinal(GI) tract, achieving the excellent obstacle surmounting ability in the GI complex environment with the less twisted impact on the GI tract, which has a promising application prospect in the GI diagnosis.

Kinematic characterization and optimization of vehicle front-suspension design based on ADAMS

To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of ?10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm; this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle.

Optimal Driving of Large Belt Conveyor with Multi-roller Variable-Frequency Drive

in this paper, an electromechanically coupled mathematic model of multi-roller driving system for belt conveyor is set up, and the computing equations for dynamic displacement and dynamic tension of the conveyor are also formulated when the hoister is used for straining. Based on the belt conveyor of main inclined shaft in Chengzhuang coal mine, the driving torque, driving power and starting-speed characteristic of each electric motor are studied and measured when multi-roller variable-frequency drive (power distribution 2∶1) is used. The optimal control and the optimal starting-acceleration of the multi-roller variable-frequency drive are determined by a large number of industrial experiments and theoretical calculations.

Study on Outboard Inductive Damping Valve in Hydro-pneumatic Suspension

A new outboard inductive damping valve without any electronic control system is developed. Its working principle,structure and external characteristic are studied. Its mathematical model is presented and its damping characteristic is investigated on the basis of fluid continuity equation,differential equations of motion and Bernoulli equation. The influence of the valve parameters on the damping characteristic is studied numerically. The effects of outboard inductive damping valve and common damping valve on ride and tire load are compared also. The external characteristic of the valve is verified in bench test. The results show that the valve’s mathematical model is quite accurate and the developed valve can be adjust in two stages,which can also meet the requirements of the dynamic characteristic of the vehicle suspension system.

Basic Problems in Design and Inverse Engineering Solution for Outer Characteristic of Vehicle Suspension Shock Absorbers

Based on the theory and the practical experiences of linearity design of feasible design area and inverse solution of non linear outer characteristic of suspension shock absorber, in accordance with non linearity outer characteristic formed by open up damping coefficient, full open damping coefficient and smoothness to safety ratio of suspension shock absorber, a method and a research conclusion of the feasible design and inverse solution for the basic problems of designing and inverse solution of non linear outer characteristic of suspension damping components are provided.

高温超导直线同步电机电磁力仿真与实验研究

无铁芯超导直线同步电机(superconducting linear synchronous motor,SLSM)具有推力密度高、工作气隙大等优势,是超导磁浮列车的动力核心。由于会不可避免地受到弯道、道岔、横风和电源谐波等因素的影响,磁浮列车在运行过程中将发生多自由度运动,使电机次级姿态发生滚转或偏移,致使超导直线电机的电磁力性能发生改变,进而影响列车的运行稳定性。针对多变电机次级姿态下高温超导直线同步电机的三维力特性展开研究,首先分析悬浮车体多自由度运动对直线电机次级姿态的影响,并建立计算SLSM三维电磁力的有限元模型;其次,通过搭建超导同步直线电机样机,实验验证模型的有效性;最后,基于该模型研究无铁芯SLSM次级在发生横向偏移、法向偏移、侧滚、俯仰以及偏航条件下的三维电磁力输出特性及其变化规律,为超导磁浮列车运行性能优化提供了理论依据。

矿井带式输送机火灾烟流特性及其预警防控综述

为有效防控煤矿井下带式输送机火灾事故,保障煤矿工作人员的生命财产安全,系统分析矿井带式输送机火灾的起火原因、燃烧特性、烟流特性、监测预警技术及防治措施,并基于当前研究现状提出展望。结果表明:引发带式输送机火灾的主要原因是摩擦温升、电气设备故障及明火;研究带式输送机火灾燃烧和烟流特性采用的巷道火灾模型及数值模拟相关参数具有一定局限性,需综合考虑运输巷道实际工况及环境等参数;国内虽有针对带式输送机火灾的监测预警系统,但其尚有不足,需引入5G、大数据及人工智能等新兴技术予以完善,并结合硬件探测及人员管理等方面,健全煤矿带式输送机火灾防治体系,进而全面推动煤矿安全智能化建设。

流化床反应室内铁矿石的临界流化特性

U型反应室是悬浮焙烧装备的核心部件,明确其内物料的临界流化特性具有理论与实践意义.为此,自行搭建了冷态试验系统,并以赤铁矿粉、氧化铝粉为原料,研究了松动风量、物料性质对物料临界流化特性的影响规律,并对原有经验公式进行了修正.结果表明:临界流化气速随物料粒度、密度的增加而增加;在松动室床层为固定床的条件下,临界流化气速随松动风量的增大而减小;修正后的过程方程与试验数据吻合较好,可用于反应室内物料流化行为的预测.研究结果利于悬浮磁化焙烧技术实体化,对该技术工业应用具有一定的指导意义.

高机动越野平台非线性悬挂特性控制方法

为了提升装备机动能力,基于摆动缸式油气悬挂装置,建立高压气动原理和背压可控的阻尼阀结构,实现刚度和阻尼特性的实时调节。基于单轮悬挂模型开展不同刚度控制方法的振动响应对比分析以及阻尼特性频域不动点推导,提出一种刚度有级调节控制策略和一种频域混合阻尼控制方法,通过单轮悬挂动力学模型验证所提控制方法的有效性,并构建高机动履带车辆动力学模型进行整车仿真分析。在康庄、羊八井、坨里实测路面环境下,采用刚度阻尼联合控制方法的悬挂装置相较于传统被动悬挂的越野速度提升了25%以上,验证了新提出特性控制方法对振动响应抑制的优越性,能够为悬挂装置实现弹性与阻尼双特性自适应调节提供支撑。

悬索桥基频影响因素的参数化分析与实用计算

桥梁设计师常常采用简化(实用)公式估算桥梁基频,用以在大跨桥梁设计的前期阶段估算其动力性能。但是随着桥梁建设的发展,部分公式的精度已无法满足要求;在实际使用时各公式易用性也存在较大差异。本文在分析各基频估算公式误差来源的基础上,选择关键变量、采用参数化有限元模型分析各控制因素的影响效应,据此选择改进策略,同时在分析各参数相互关系的基础上进行变量精简,提升估算公式的易用性。经实测和计算基频值的验证,改进实用计算公式在提高了易用性和适用性的同时,有效控制了基频估算结果的整体误差极值,提升了基频估算公式的工程应用价值。