Time Domain Identification of Moving Loads on Bridge Deck

2003 ◽  
Vol 125 (2) ◽  
pp. 187-198 ◽  
Author(s):  
X. Q. Zhu ◽  
S. S. Law
Keyword(s):  
Time Domain ◽  
Orthotropic Plate ◽  
Bridge Deck ◽  
Vibration Mode ◽  
Plate Theory ◽  
Moving Loads ◽  
Regularization Technique ◽  
Domain Identification ◽  
Fixed Distance ◽  
Superposition Technique

A new time domain method is presented to identify moving loads on a bridge deck based on the measured responses. The bridge deck is modeled as an orthotropic plate and the loads are modeled as a group of four loads moving on top of the bridge deck at fixed distance apart. Dynamic behavior of the bridge deck is analyzed by the orthotropic plate theory and mode superposition technique. Like all inverse problems, this identification is an ill-conditioned problem, and a regularization technique is employed to stabilize the computations. The identified loads moving at different eccentricities are presented. Laboratory work on the force identification is also presented. The effect of incomplete measured modes in the responses is discussed, and an underestimation in the loads may result if the number of vibration mode for identification is larger than that in the responses. Computational simulations and laboratory tests show that the method is effective and practical for identification of individual wheel loads on bridge decks.

Identification of Moving Loads on an Orthotropic Plate

2000 ◽  
Vol 123 (2) ◽  
pp. 238-244 ◽  
Author(s):  
X. Q. Zhu ◽  
S. S. Law
Keyword(s):  
Prior Knowledge ◽  
Tikhonov Regularization ◽  
Time Domain ◽  
Orthotropic Plate ◽  
Superposition Principle ◽  
Dynamic Responses ◽  
Moving Loads ◽  
Strain Measurements ◽  
Regularization Procedure ◽  
The Time Domain

A method is presented to identify indirectly loads moving on an orthotropic plate. The loads are in a group of two forces or four forces. The dynamic behavior of the plate under the action of these moving loads is analyzed. A method to identify these moving forces from the dynamic responses of the plate is developed basing on the modal superposition principle, and Tikhonov regularization procedure is applied to provide bounds to the solution in the time domain. Prior knowledge on the modal properties of the plate and the velocity of loads is required. The errors in the identified individual loads are discussed. The effect of different combinations of measuring locations on the identification is studied. Numerical results show that acceleration responses would give better and acceptable results than strain measurements.

Control of Vibrations due to Moving Loads on Suspension Bridges

2006 ◽  
Vol 11 (3) ◽  
pp. 293-318 ◽  
Author(s):  
M. Zribi ◽  
N. B. Almutairi ◽  
M. Abdel-Rohman
Keyword(s):  
Bridge Deck ◽  
Suspension Bridge ◽  
Lyapunov Theory ◽  
Dynamic Responses ◽  
Suspension Bridges ◽  
Control Force ◽  
Moving Loads ◽  
Hydraulic Actuator ◽  
Long Span ◽  
Suspended Cables

The flexibility and low damping of the long span suspended cables in suspension bridges makes them prone to vibrations due to wind and moving loads which affect the dynamic responses of the suspended cables and the bridge deck. This paper investigates the control of vibrations of a suspension bridge due to a vertical load moving on the bridge deck with a constant speed. A vertical cable between the bridge deck and the suspended cables is used to install a hydraulic actuator able to generate an active control force on the bridge deck. Two control schemes are proposed to generate the control force needed to reduce the vertical vibrations in the suspended cables and in the bridge deck. The proposed controllers, whose design is based on Lyapunov theory, guarantee the asymptotic stability of the system. The MATLAB software is used to simulate the performance of the controlled system. The simulation results indicate that the proposed controllers work well. In addition, the performance of the system with the proposed controllers is compared to the performance of the system controlled with a velocity feedback controller.

A Frequency Domain Versus a Time Domain Identification Technique for Nonlinear Parameters Applied to Wire Rope Isolators

2000 ◽  
Vol 123 (4) ◽  
pp. 645-650 ◽  
Author(s):  
Gaetan Kerschen ◽  
Vincent Lenaerts ◽  
Stefano Marchesiello ◽  
Alessandro Fasana
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Nonlinear Dynamical Systems ◽  
Wire Rope ◽  
Restoring Force ◽  
Nonlinear Parameters ◽  
Nonlinear Dynamical ◽  
Domain Identification ◽  
Identification Technique ◽  
Reverse Path Method

The present paper aims to compare two techniques for identification of nonlinear dynamical systems. The Conditioned Reverse Path method, which is a frequency domain technique, is considered together with the Restoring Force Surface method, a time domain technique. Both methods are applied for experimental identification of wire rope isolators and the results are compared. Finally, drawbacks and advantages of each technique are underlined.

scholarly journals Synchronous machine parameter identification in frequency and time domain

2007 ◽  
Vol 4 (1) ◽  
pp. 51-69 ◽  
Author(s):  
M. Hasni ◽  
S. Djema ◽  
O. Touhami ◽  
R. Ibtiouen ◽  
M. Fadel ◽  
...  
Keyword(s):  
Time Domain ◽  
Synchronous Machine ◽  
Model Structure ◽  
Machine Parameter ◽  
Identification Procedure ◽  
Time Constants ◽  
Domain Identification ◽  
Salient Pole ◽  
Salient Pole Synchronous Machine ◽  
Input Signals

This paper presents the results of a frequency and time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. The objective of this study is to use several input signals to identify the model structure and parameters of a salient-pole synchronous machine from standstill test data. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We estimate the parameters of operational impedances, or in other words the reactance and the time constants. The tests were carried out on synchronous machine of 1.5 kVA 380V 1500 rpm.

Water Entry of a Wedge by Hydroelastic Orthotropic Plate Theory

1999 ◽  
Vol 43 (03) ◽  
pp. 180-193 ◽  
Author(s):  
Odd M. Faltinsen
Keyword(s):  
Impact Velocity ◽  
Cross Sections ◽  
Orthotropic Plate ◽  
Plate Theory ◽  
Three Dimensional ◽  
Water Entry ◽  
Natural Period ◽  
Cross Sectional ◽  
Flow Effects ◽  
The Impact

Water entry of a hull with wedge-shaped cross sections is analyzed. The stiffened platings between two transverse girders on each side of the keel are separately modeled. Orthotropic plate theory is used. The effect of structural vibrations on the fluid flow is incorporated by solving the two-dimensional Laplace equation in the cross-sectional fluid domain by a generalized Wagner's theory. The coupling with the plate theory provides three-dimensional flow effects. The theory is validated by comparison with full-scale experiments and drop tests. The importance of global ship accelerations is pointed out. Hydrodynamic and structural error sources are discussed. Systematic studies on the importance of hydroelasticity as a function of deadrise angle and impact velocity are presented. This can be related to the ratio between the wetting time of the structure and the greatest wet natural period of the stiffened plating. This ratio is proportional to the deadrise angle and inversely proportional to the impact velocity. A small ratio-means that hydroelasticity is important and a large ratio means that hydroelasticity is not important.

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