COMPUTER-AIDED ANALYSIS OF URBAN RAILWAY VEHICLES

Computer-aided dynamic simulations are usually employed when designing modem urban railway vehicles. Even if the modeling procedure is simil ar to the one used for trains, specific features have to be taken into account for tramways: they are designed for low speeds (less than 80 km/h) and narrow curves (less than 20 m of radius). Moreover, in order to improve accessibility, low floor designs have been developed (the floor lying at about 300 mm above the rails level). The simulation pro cedure has therefore to take account of the occurence of multiple whee l/rail contacts or the modelization of independent wheels. A specific software well adapted to the computer-aided design of urban railway ve hicles has been developed by the Faculte Polytechnique de Mons. It per forms the following classical analyses: lateral linearization, modal a nalysis and root locii plots; vertical linearization and comfort predi ction; non-linear time simulation in straight track (limit cycles) and in curve (derailment study); parametric analyses. The vehicle model i s formed by combination of bodies (rigid or flexible bodies, rotating bodies like wheelsets or independent wheels) and interconnection eleme nts (spring and damper elements). Contact between rails and wheels is treated as a part of the rotating bodies. A residual formulation has b een preferred. When combined with the use of a complete iteration matr ix, this formulation is well adapted to the treatment of stiff differe ntial equations. It is based on a fast determination of the residues o f the dynamic equations combined with the calculation of the iteration matrix through a numerical derivation procedure. The advantages of th e approach are discussed. The model of a partial low floor vehicle wit h wheelsets and independent wheels is described.