Abstract
Keywords: torsion eigenvalues, modal, bus structure, finite element
Nowadays, rollover of heavy vehicles is one the main causes of accidents. Recent investigations have been carried out to predict rollover limit (Diaz et al., 2004). A vehicle starts rollover when the lateral acceleration is above the so called rollover limit. One of the parameters that influence rollover limit is the bus torsion stiffness. In fact, increasing torsion stiffness, the rollover limit is also increased. Kim (1993) and Lan et al. (2004) optimized the bending and torsion stiffness of a bus structure by means of a finite element model, due to the fact that the finite element method has been validated by numerous experimental tests (Sun et al., 1999; Feng, 1999; Pine et al., 1999; Lee et al., 2000). Thompson et al. (1998) optimized vehicle weight and improved torsion stiffness in a sport vehicle, for which torsion stiffness is of paramount importance for handling. Subic, A. and Jimin, H. (1997) improved bus rollover design through modal analysis.
Not only torsion stiffness has to be evaluated due to its influence on rollover but the eigenvalues have to be analysed so that it is not coincident with road excitements. Therefore, in this paper it is proposed a torsion model of a real bus structure that allows torsion eigenvalues calculation. Eigenvalues have been compared with those obtained using a developed finite element model which was previously validated by torsion static tests.