A General Purpose Computer Program for the Dynamic Simulation of Vehicle-Guideway Interactions

Abstract

A general purpose computer program for calculating the dynamic response of vehicles traveling over surface or evaluated guideways is described. The program has application to a broad class of transportatio n systems and hence eliminates the need for numerous specialized programs. The program is modular in design and is based on the finite element or building block method in which a complex dynamic system is made up of a number of components. The equations of motion for each of these components is known, and the program automatically combines the component equations to form equations of motion for the complete system. The equations of motion are then integrated numerically to give the response of the system to variables such as guideway roughness, span length, etc. Several output options are available and on-line printer plots or off-line CalComp plots of the response can be obtained. Addition building blocks can be easily added to.the program whenever desired. The program is written in PL/I language and has been used on the IBM 360/91 computer. The program has been used on a limited number of problems, several of which are included in this paper. GENERAL purpose computer program (APLDYN)1 has been written for the simulation of the dynamics associated with vehicles traveling over surface or elevated guideways with prescribed irregularities. The program has application to a broad class of transportation systems and hence eliminates the need for numerous specialized programs. It is based on the finite element method in which a complex system is made up of a number of discrete components. This technique is not new to the structural engineer, but it has seen limited application to dynamic problems associated with discrete moving masses. The APLDYN application of this finite element technique to moving vehicle problems is similar to, but more general than that used by Hunt 2 to determine the dynamic response of a flexible vehicle moving along a flexible supporting structure. Other simulations3 ~~ 5 although useful for studying the dynamic behavior of specific systems, have been limited in scope and versatility. Kaplan et al. 3 have developed a simulation for the vertical response of a single car or a two-car train traveling across an elevated guideway with no irregularities. The guideway flexibility provides the dynamic ex citation. McHenry and Deleys4 have written a simulation for the response of automobiles when encountering obstacles such as guard rails, railroad crossings and abutments. The simulation does not handle the more general class of vehicles, elevated guideways, and roadbed irregularities encountered in new transportation systems. Melpar has also developed a comprehensive computer program5 but this program is written specifically for a conventional railcar on a surface track. The Melpar program handles a multidegree-of -freedom system but is limited in the number of mass elements that can be simulated.