Dynamic response of a beam on a frequency-independent damped elastic foundation to moving load

2003 ◽  
Vol 30 (2) ◽  
pp. 460-467 ◽  
Author(s):  
Seong-Min Kim ◽  
Jose M Roesset
Keyword(s):  
Fourier Transform ◽  
Elastic Foundation ◽  
Moving Load ◽  
Harmonic Load ◽  
Moving Loads ◽  
Constant Amplitude ◽  
Maximum Displacement ◽  
Initial Application ◽  
Frequency Independent ◽  
Double Fourier Transform

The dynamic displacement response of an infinitely long beam on an elastic foundation with frequency-independent linear hysteretic damping subjected to a constant amplitude or a harmonic moving load was investigated. The advance velocity was assumed to be constant. Formulations were developed in the transformed field domain using (i) a Fourier transform in moving space for moving loads of constant amplitude, (ii) a double Fourier transform in time and moving space for moving loads of arbitrary amplitude variation or to include the transient due to the initial application of the load for moving harmonic loads, and (iii) a Fourier transform in moving space for the steady-state response to moving harmonic loads. The effects of velocity, damping, loaded length, and load frequency on the deflected shape and the maximum displacement were investigated. The critical (resonant) velocities and frequencies were obtained by analyses, and expressions to find them were suggested.Key words: beam on elastic foundation, damping, Fourier transform, frequency, harmonic load, moving load, transformed field, velocity.

Dynamic Responses of Functionally Graded Sandwich Beams Resting on Elastic Foundation Under Harmonic Moving Loads

2018 ◽  
Vol 18 (09) ◽  
pp. 1850112 ◽  
Author(s):  
Wachirawit Songsuwan ◽  
Monsak Pimsarn ◽  
Nuttawit Wattanasakulpong
Keyword(s):  
Boundary Conditions ◽  
Elastic Foundation ◽  
Natural Frequencies ◽  
Moving Load ◽  
Beam Theory ◽  
Equation Of Motion ◽  
Functionally Graded ◽  
Dynamic Responses ◽  
Harmonic Load ◽  
Sandwich Beams

This paper investigates the free vibration and dynamic response of functionally graded sandwich beams resting on an elastic foundation under the action of a moving harmonic load. The governing equation of motion of the beam, which includes the effects of shear deformation and rotary inertia based on the Timoshenko beam theory, is derived from Lagrange’s equations. The Ritz and Newmark methods are employed to solve the equation of motion for the free and forced vibration responses of the beam with different boundary conditions. The results are presented in both tabular and graphical forms to show the effects of layer thickness ratios, boundary conditions, length to height ratios, spring constants, etc. on natural frequencies and dynamic deflections of the beam. It was found that increasing the spring constant of the elastic foundation leads to considerable increase in natural frequencies of the beam; while the same is not true for the dynamic deflection. Additionally, very large dynamic deflection occurs for the beam in resonance under the harmonic moving load.

Dynamics of Plate Generated by Moving Harmonic Loads

2005 ◽  
Vol 72 (5) ◽  
pp. 772-777 ◽  
Author(s):  
Lu Sun
Keyword(s):  
Moving Load ◽  
Point Load ◽  
Harmonic Load ◽  
Maximum Displacement ◽  
Moving Vehicle ◽  
Vehicle Load ◽  
Airport Pavement ◽  
Winkler Elastic Foundation ◽  
Approximate Relationship ◽  
Moving Harmonic Load

A thin plate resting on a Winkler elastic foundation subject to a moving harmonic load can be used as the model for highway and airport pavement under moving vehicle load and many other applications. The study of dynamic response of the plate thus becomes very important. In this paper we study the dynamic displacement of a plate caused by a moving harmonic line and point load. The solution is represented by the convolution of dynamic Green’s function of plate. An approximate relationship between critical load velocity and critical frequency is established analytically. It is found that the maximum displacement response occurs at the center of the moving load and travels at the same speed with the load.

Experimental Simulation of Bridges Subjected by Moving Loads

2017 ◽  
Vol 873 ◽  
pp. 208-211
Author(s):  
Zhang Jun ◽  
Ming Kang Gou ◽  
Chuan Liang
Keyword(s):  
Laboratory Experiments ◽  
Moving Load ◽  
Beam Theory ◽  
Dynamic Responses ◽  
Experimental Simulation ◽  
Analytic Method ◽  
Harmonic Load ◽  
Moving Loads ◽  
Material Resource ◽  
Simply Supported

The effect of bridge vibrationinduced bylive loads such as vehicles and pedestrians is an important factor of bridge fatigue damage. It takes much labor and material resource to perform vibration experiments on bridges subjected by real moving loads in field. In order to carry out laboratory experiments on bridges subjected by moving loads, a fixed load with harmonic vibration simulates a moving load on bridge in the beam theory. A simply supported bridge is considered in the present study. The dynamic responses of bridge under different loads are established by the analytic method. Amplitude and frequency of the simulated load are generated on the principle of equal displacements due to both a moving load and a fixed harmonic load impacting on a simply supported beam. Comparisons of numerical results of two types of load on the same beam indicate that the harmonic load can simulate a moving load effectively. It is possible that the field test on bridge can be carried out indoors.

An automatic means to discriminate between earthquakes and quarry blasts

1990 ◽  
Vol 80 (6B) ◽  
pp. 2143-2160
Author(s):  
Michael A. H. Hedlin ◽  
J. Bernard Minster ◽  
John A. Orcutt
Keyword(s):  
Fourier Transform ◽  
Spectral Features ◽  
Single Event ◽  
Vertical Array ◽  
Signal To Noise ◽  
Spectral Character ◽  
Frequency Pattern ◽  
Time Frequency ◽  
Cepstral Analysis ◽  
Double Fourier Transform

Abstract In this article we discuss our efforts to use the NORESS array to discriminate between regional earthquakes and ripple-fired quarry blasts (events that involve a number of subexplosions closely grouped in space and time). The method we describe is an extension of the time versus frequency “pattern-based” discriminant proposed by Hedlin et al. (1989b). At the heart of the discriminant is the observation that ripple-fired events tend to give rise to coda dominated by prominent spectral features that are independent of time and periodic in frequency. This spectral character is generally absent from the coda produced by earthquakes and “single-event” explosions. The discriminant originally proposed by Hedlin et al. (1989b) used data collected at 250 sec−1 by single sensors in the 1987 NRDC network in Kazakhstan, U.S.S.R. We have found that despite the relatively low digitization rate provide by the NORESS array (40 sec−1) we have had good success in our efforts to discriminate between earthquakes and quarry blasts by stacking all vertical array channels to improve signal-to-noise ratios. We describe our efforts to automate the method, so that visual pattern recognition is not required, and to make it less susceptible to spurious time-independent spectral features not originating at the source. In essence, we compute a Fourier transform of the time-frequency matrix and examine the power levels representing energy that is periodic in frequency and independent of time. Since a double Fourier transform is involved, our method can be considered as an extension of “cepstral” analysis (Tribolet, 1979). We have found, however, that our approach is superior since it is cognizant of the time independence of the spectral features of interest. We use earthquakes to define what cepstral power is to be expected in the absence of ripple firing and search for events that violate this limit. The assessment of the likelihood that ripple firing occurred at the source is made automatically by the computer and is based on the extent to which the limit is violated.

scholarly journals Dynamic Behavior of Tied-Arch Bridges under the Action of Moving Loads

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Paolo Lonetti ◽  
Arturo Pascuzzo ◽  
Alessandro Davanzo
Keyword(s):  
Dynamic Behavior ◽  
Structural Characteristics ◽  
Moving Load ◽  
Sensitivity Analyses ◽  
Impact Factors ◽  
Moving Loads ◽  
Centripetal Acceleration ◽  
Design Variables ◽  
Dynamic Amplification ◽  
Arch Bridges

The dynamic behavior of tied-arch bridges under the action of moving load is investigated. The main aim of the paper is to quantify, numerically, dynamic amplification factors of typical kinematic and stress design variables by means of a parametric study developed in terms of the structural characteristics of the bridge and moving loads. The basic formulation is developed by using a finite element approach, in which refined schematization is adopted to analyze the interaction between the bridge structure and moving loads. Moreover, in order to evaluate, numerically, the influence of coupling effects between bridge deformations and moving loads, the analysis focuses attention on usually neglected nonstandard terms in the inertial forces concerning both centripetal acceleration and Coriolis acceleration. Sensitivity analyses are proposed in terms of dynamic impact factors, in which the effects produced by the external mass of the moving system on the dynamic bridge behavior are evaluated.

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