The Analysis and Creation of Track Irregularities Using TRAKVU

Abstract

<P>The accuracy of the results from a rail vehicle dynamic model is dependent

on the realism of the track input to the model. An important part of the

track input is the irregularities that exist on actual track. This study

analyzes the irregularities inherent in railroad track geometry data, and

provides an analytical method for creating track data with the irregularities

for use as the input to a dynamic model. </P>

<P>Track data, measured from various classes of track, was examined using

statistical and frequency analysis techniques to identify any similarities

in the characteristics of the irregularities. The results showed that each

class of track had a distinctive value for the standard deviation of the

alignment and profile data. It was also determined that the frequency content

of all the tracks was contained within a common bandwidth. The track irregularities

could then be generated with the same characteristics as an actual track.</P>

<P>The method for creating the track irregularities was then programmed

into TRAKVU. TRAKVU is a track preprocessor used in conjunction with NUCARS,

a railcar dynamic modeling program<SUP>1</SUP>. TRAKVU enables users to

create track data and apply the appropriate irregularities so that the

track will have the characteristics of the desired class of track.</P>

<P>A validation was then performed to determine how well track created

in TRAKVU simulated actual tracks. The statistical and frequency characteristics

of created tracks were compared directly with actual tracks. Created track

was also used as the input to a dynamic model. The predicted vehicle response

was then compared to the actual vehicle response and the predicted vehicle

response using measured track data as the input. The results from the validation

showed that the created track performed as well as the measured track in

providing the input to the model. Although the predicted response using

the created track did not compare as well with the actual vehicle response,

the differences could be attributed to inaccuracies in the model.</P>

<P><FONT SIZE=-1><SUP>1</SUP> NUCARS&amp;nbsp;and TRAKVU are copyrighted property

of the Association of American Railroads</FONT></P>