Curved bridge response to a moving vehicle

An algorithm is developed for the solution of the dynamic displacement and rotation of a horizontal curved guideway (bridge) as it interacts with a traversing vehicle. The algorithm is validated against experimental results, and a parametric study is presented.     

Reduction of bridge dynamic amplification through adjustment of vehicle suspension damping

This paper presents a novel approach to the reduction of short-span bridge dynamic responses to heavy vehicle crossing events. The reductions are achieved through adjustment of the vehicle suspension damping coefficient just before the crossing. Given pre-calculations of the response of a vehicle-bridge system to a set of ‘unit’ road disturbances, it is shown that a single optimum damping coefficient may be determined for a given velocity and any specified road profile. This approach can facilitate implementation since the optimum damping is selected prior to the bridge and there is no need to continuously vary the damping coefficient during the crossing. The concept is numerically validated using a bridge-vehicle interaction model with several road profiles, both measured and artificially generated. The bridge-friendly damping control strategy is shown to reduce bridge dynamics across a typical range of vehicle velocities, proving most effective for road profiles that induce large vibrations in the vehicle-bridge system.     

A finite element method prediction of the vibration of a bridge subjected to a moving vehicle load

This paper is concerned with the analysis of dynamic deflection and acceleration of a concrete bridge which is subjected to a moving vehicle load. The bridge, to be constructed across the River Brahmaputra in India, consists of 20 main spans, and each main span is assumed to be double cantilever type with a small suspended span. The moving vehicle is modeled as one degree of freedom. The deflections and accelerations at specific locations on the bridge when the vehicle moves at constant speed are analyzed by using the finite element method.     

Dynamic response of a monorail steel bridge under a moving train

This study proposes a dynamic response analysis procedure for traffic-induced vibration of a monorail bridge and train. Each car in the monorail train is idealized as a dynamic system of 15-degrees-of-freedom. The governing equations of motion for a three-dimensional monorail bridge-train interaction system are derived using Lagrange's formulation for monorail trains, and a finite-element method for modal analysis of monorail bridges. Analytical results on dynamic response of the monorail train and bridge are compared with field-test data in order to verify the validity of the proposed analysis procedure, and a positive correlation is found. An interesting feature of the monorail bridge response is that sway motion is caused by torsional behavior resulting from eccentricity between the shear center of the bridge section and the train load.     

A study on radial directional natural frequency and damping ratio in a vehicle tire

The measurement of radial directional natural frequency and damping ratio in a vehicle tire has been studied. Natural frequencies and damping ratios in the radial direction of various tires, from passenger car tires to truck bus tires, are reported. The radial direction modal parameters of tires subjected to different levels of inflation pressure, have been determined by using a frequency response function method. To obtain the theoretical natural frequency and mode shape, the plane vibration of a tire has been modeled as though it were that of a circular beam. By using the Tielking method that is based on Hamilton’s principle, theoretical results have been determined by considering the rotational velocity, tangential and radial stiffness, radial directional velocity and tension force which is due to tire inflation pressure. The results show that experimental conditions can be considered as the parameters that shift the natural frequency and damping ratio.     

Nonlinear interaction between a moving vehicle and a plate elastically mounted on a tunnel

The paper presents a theoretical study of the interaction between a nonlinear model of a moving vehicle (velocity v) and a plate elastically mounted in a tunnel. An efficient approach to the solution of the problem of vehicle-slab-track-tunnel-soil interaction is developed on the basis of a coupling of the Finite Element and Integral Transform methods (FEM and ITM). According to this approach the tunnel which may have an arbitrary shape and a portion of the surrounding soil is modelled by Finite Elements while the soil (half-space) is described by the ITM. The corresponding solution is found using the solutions for the uniform half-space and for the continuum with a cylindrical cavity. To exploit the invariance of the structure in longitudinal direction x, for this direction additionally to the time-frequency transform (tω) a space-wavenumber transform (xk_x) is used. The case of a half-space is analyzed using a Fourier transform also in the second horizontal direction (yk_y) and an analytical solution for the z-direction on the basis of exponential functions. In the case of the infinite continuum with the cavity a Fourier series (for the circumferential direction) and a series of cylindrical functions (for the radial direction) are used for the solution regarding the cross-sectional coordinates (y,z). The tunnel structure, that may have an arbitrary shape, and a portion of the surrounding soil will be modelled by Finite Elements in a (xk_x,tω) transformed domain.In order to observe the boundary conditions at the surface of the half-space as well as at the surface of the cavity, the superposition of the two solutions has to be performed after an inverse Fourier transform (IFT) in the (k_x,y,z,ω)-domain.The solution for the complete system floating slab-track-tunnel-half-space is obtained in the (k_x,y,z,ω)-domain. Once the system transfer function H(ω^′) (with ω^′=ω+vk_x) for this complete coupled system is found, the displacements of the plate can be calculated in time domain by the IFT of the product p(ω^′)H(ω^′), i.e. the convolution of the loading p(t) with the impulse response function h(t), which completely represents the behavior of the coupled system. In the context of the coupling of systems in a relative movement the problems of differential algebraic equations (DAE) have to be observed.     

Identification of the structure parameters applying a moving load

An approach to the flexural stiffness identification of a linear structure is proposed. The idea of the presented approach is to transform the dynamical problem into a static one by integrating the input and output signals. The output signal is the structure displacement due to different kinds of loads such as a pulse acting at a given point, moving a load of deterministic or random type. The obtained solution for the one-point force can be easily generalized to a set of point forces, which can be a model of the pressure of vehicle axes. The presented method can be applied to the identification of structure parameters of bridges. It allows also to take into account some stochastic disturbances following the movement of vehicles through the pavement roughness.     

Response of a continuous guideway on equally spaced supports traversed by a moving vehicle

An algorithm is developed to analyze the dynamic response of a continuous guideway resting on equally spaced supports being traversed by a moving vehicle. A critical speed, one at which the amplitude of the guideway displacement becomes large, is determined. The critical speed corresponds to the slowest possible speed at which a transverse wave can propagate longitudinally in the guideway structure. A parametric study is also presented.     

Identification of stiffness and damping properties of plates by using the local equation of motion

This paper deals with the identification of stiffness and damping properties of vibrating structures by an inverse method inspired from the Force Analysis Technique (FAT). The proposed approach uses a local equation of motion assumed a priori, which provides a relative straightforward relationship between the displacement field and material properties. The spatial derivatives of the displacement in the equation are calculated using finite differences. As this operation amplifies measurement noise, a regularization step is applied before solving the inverse problem. A procedure is proposed to automatically adjust the level of regularization. The method also allows one to identify local stiffness and damping on a heterogeneous structure. Illustrations for both homogeneous and heterogeneous cases are shown using simulated and measured displacement fields.     

Symplectic random vibration analysis of a vehicle moving on an infinitely long periodic track

Based on the pseudo-excitation method (PEM), symplectic mathematical scheme and Schur decomposition, the random responses of coupled vehicle-track systems are analyzed. The vehicle is modeled as a spring-mass-damper system and the track is regarded as an infinitely long substructural chain consisting of three layers, i.e. the rails, sleepers and ballast. The vehicle and track are coupled via linear springs and the “moving-vehicle model” is adopted. The latter assumes that the vehicle moves along a static track for which the rail irregularity is further assumed to be a zero-mean valued stationary Gaussian random process. The problem is then solved efficiently as follows. Initially, PEM is used to transform the rail random excitations into deterministic harmonic excitations. The symplectic mathematical scheme is then applied to establish a low degree of freedom equation of motion with periodic coefficients. In turn these are transformed into a linear equation set whose upper triangular coefficient matrix is established using the Schur decomposition scheme. Finally, the frequency-dependent terms are separated from the load vector to avoid repeated computations for different frequencies associated with the pseudo-excitations. The proposed method is subsequently justified by comparison with a Monte-Carlo simulation; the fixed-vehicle model and the moving-vehicle model are compared and the influences of vehicle velocity and class of track on system responses are also discussed.     

Measurement of specimen permittivity using a waveguide bridge

The proposed method for measuring the permittivity of the medium in the superhigh frequency band makes use of the depolarizing effect of the electromagnetic field. Upon exposing a dielectric particle to an electromagnetic field having a definitely oriented electric-field intensity vector, E_n, the reflected electric-field intensity vector, E₀, will not, in general, coincide in direction with the incident field (as a result of depolarization). This depolarization depends upon the form and dimensions of the particle, on its permittivity, and on the wavelength.     

Measurement of sound intensity using a single moving microphone

A method for measuring sound intensity by using a single moving microphone is proposed. Experiments that confirm the validity of this method are reported and the advantages and disadvantages of the method are discussed.     

Vibration control of beams on elastic foundation under a moving vehicle and random lateral excitations

The formulation of three-dimensional dynamic behavior of a Beam On Elastic Foundation (BOEF) under moving loads and a moving mass is considered. The weight of the vehicle is modeled as a moving point load, however the effect of the lateral excitation is considered by modeling: (case 1) a lateral moving load with random intensity for wind excitation and (case 2) a moving mass just in lateral direction of the beam for earthquake excitation. A Dirac-delta function is used to describe the position of the moving load and the moving mass along the beam. The beam foundations are considered as elastic Winkler-type in two perpendicular transverse directions. This model is proposed to investigate the bending response of the rails under the effect of traveling vehicle weight while a random excitation such as earthquake or wind takes place. The results showed the importance of considering the effect of earthquake/wind actions as in bending stress of the beam on elastic foundations. The effect of different regions (different support stiffness) and different velocities of the vehicle on the response of the beam are investigated in mentioned directions. At the end, a linear optimal control algorithm with displacement–velocity feedback is proposed as a solution to suppress the response of BOEFs. By the method of modal analyses and taking into account enough number of vibration modes, state-space equation is obtained, then sufficient number of actuators was chosen for each direction. Stochastic analyses were performed in lateral direction in order to illustrate a comprehensive view for the response of the beam under the random moving load in both controlled and uncontrolled systems. Furthermore, the efficiency of control algorithm on critical velocities is verified by parametric analyses in the vertical direction with the constant moving load for different regions.     

3D numerical model of the electrostatic coating process with moving objects using a moving mesh

In this paper, a full three dimensional FLUENT numerical model of the electrostatic coating process with the embedded moving mesh capability and piecewise linear type target motion is presented. The model includes target geometries that do not exhibit symmetry. All the dominant mechanical and electrical phenomena are taken into account. Mechanical phenomena include shaping air effects, downdraft effects and the motion of the polydispersed particles. Electrical phenomena include the particle space charge distribution, corona discharge and the electrohydrodynamic flow effects. It was demonstrated that the numerical model can accurately mimic the type of the motion used in real world applications.     

运动小孔径水平基阵估计目标深度

针对浅海动态声场,基于简正波模型提出了一种利用运动小孔径水平基阵估计目标深度的方法。通过合成孔径算法将运动小孔径水平基阵扩展成虚拟的大孔径水平基阵,利用稀疏近似最小方差准则可以在相对较小的合成孔径上估计各阶简正波模态能量,不同深度的模态匹配度由Camberra距离的负指数度量,目标深度估计结果是模态匹配度最大值对应深度。数值仿真与实验结果表明,在简正波声场结构基础上,声源频率越低则实现目标深度估计需要的合成孔径距离越小,当声源与阵列端射方向成一定角度时,对所需合成孔径的影响与其相对速度变化时的影响相同,在典型浅海水平分层波导中,当单阵元输入信噪比为10 dB时,准确估计200 Hz和350 Hz声源的深度,分别要求合成孔径大于12倍和16倍波导深度。利用实验数据验证了该方法对水下低频线谱声源的深度估计能力。     

Dynamic measurement of room impulse responses using a moving microphone

A technique for the recording of large sets of room impulse responses or head-related transfer functions is presented. The technique uses a microphone moving with constant speed. Given a setup (e.g., length of the room impulse response), a careful choice of the recording parameters (excitation signal, speed of movement) leads to the reconstruction of all impulse responses along the trajectory. In the case of a moving microphone along a circle, the maximal angular speed is given as a function of the length of the impulse response, its maximal temporal frequency, the speed of sound propagation, and the radius of the circle. As a result of the presented algorithm, head-related transfer functions sampled at 44.1 kHz can be measured at all angular positions along the horizontal plane in less than 1 s. The presented theory is compared with a real system implementation using a precision moving microphone holder. The practical setup is discussed together with its limitations.     

Tracking individual fish from a moving platform using a split-beam transducer

Tracking of individual fish targets using a split-beam echosounder is a common method for investigating fish behavior. When mounted on a floating platform like a ship or a buoy, the transducer movement often complicates the process. This paper presents a framework for tracking single targets from such a platform. A filter based on the correlated fish movements between pings is developed to estimate the platform movement, and an extended Kalman filter is used to combine the split-beam measurements and the platform-position estimates. Different methods for gating and data association are implemented and tested with respect to data-association errors, using manually tracked data from a free-floating buoy as a reference. The data association was improved by utilizing the estimated velocity for each track to predict the location of the next observation. The data association was more robust when estimates of platform tilt/roll were used. Other techniques to estimate position and velocity, like linear regression and smoothing splines, were implemented and tested on a simulated data set. The platform-state estimation improved the estimates for methods like the Kalman filter and a smoothing spline with cross validation, but not for robust methods like linear regression and smoothing spline with a fixed degree of smoothing.     

Modeling of axially moving wire with damping: Eigenfunctions, orthogonality and applications in slurry wiresaws

The classical modal analysis is applied to derive the analytical solution and to obtain the free vibration response of damped axially moving wire in this paper. The corresponding eigenvalues, eigenfunctions, and orthogonal relationship are presented. The orthogonality property and closed-form solution of free vibration response with damping are the main contributions of this study. In addition, the analytical modal analysis, with damping factor removed, shows agreement with those in existing research literature of moving wire without damping. The specific relevance of this general solution is discussed with respect to the moving wire in a slurry wiresaw. The theoretical definition of the damping factor of the slurry wiresaw system is also provided.