Bus rollover crashworthiness under European standard: an optimal analysis of superstructure strength using successive response surface method

Bus rollover is one of the most serious of accidents. Strengthening bus frames to maintain survivor space and reduce occupant injury is necessary following the issue of Regulation No. 66 by the Economic Commission for Europe (ECE R66). Whilst increasing bus weight is unlikely because of production costs and fuel economy, this paper presents an optimal method of bus rollover crashworthiness design. In this study a full-scale, validated, finite element (FE) model of the vehicle was used. Optimisation was performed by the successive response surface method (SRSM) with LS-OPT, a design variable analysis method based on the parameterisation of the energy absorption ability of bus frame components. LS-DYNA was used as the FE solver. An optimal prototype of the vehicle was obtained with crashworthiness following ECE R66 and vehicle weight at the existing level was maintained with the improvement in the lower displacement by 49.2% and upper displacement by 39.4% of bus frames versus bus survivor space. This paper presents a procedure for bus rollover crashworthiness design related to vehicle weight, with a robust and effective method using an optimal technique combining LS-DYNA and LS-OPT.