Simplified dynamic torsional model of an urban bus

Nowadays, one of the concerns of vehicle safety is the bus rollover due to the great number of injured and deaths. The torsion stiffness of the bus structure is a parameter of security against rollover. The torsion behaviour of the bus structure is studied from a dynamic point of view. In this paper, a dynamic free vibration model, based on the Holzer method, of a bus body is proposed. Modes and natural vibration frequencies have been obtained applying the proposed model and compared with those calculated by means of a Finite Element Model (FEM) of the bus structure, which has been validated by experimental static torsion tests. Results show that the natural frequencies and modes using the proposed dynamic model agree with those obtained with the FEM.