Optimisation of Bus Superstructure for Rollover Safety According to ECE-R66

Abstract

A bus rollover is one of the most severe accidents that usually causes a large number of fatalities and injured occupants. This paper aims to investigate the key parameters affecting the damage and deformation behaviours of bus superstructure under rollover test according to Economic Commission for Europe Regulation 66 (ECE R66) as well as to design an economical lightweight bus structure by using response surface optimisation technique. The rollover simulations are performed by means of explicit dynamic analysis via Radioss finite element programme and validated by experimental data. Factorial design is implemented to pinpoint significance of each structural component based on its energy absorption under rollover condition. The significant parameters for rollover safety are found to be the stiffness of roof, pillar, and floor structures, respectively. Crashworthiness Index (CI) is proposed as an evaluation factor of overall rollover strength of bus structure. A ratio of CI to mass is proposed as an improvement criterion to supervise the progressive path of steepest descent and used to control the degree of improvement. Successive response surface optimisation via central composite design and composite desirability are employed to resolve the optimum lightweight bus structure passing ECE R66 requirements.