Abstract
Keywords - Bus rollover, Plastic hinge, UN/ECE Regulation No. 66, Safety, Database
Abstract - Rollover is among the most common form of bus accidents. Bus safety issues include, among others, the large number of passengers that can be in a bus at the same time, limited extent to which passive safety measures (safety belts, airbags, etc.) can be used, and a relatively low rollover stability of this type of vehicle. Bus construction requirements therefore include solutions for improved rollover safety as part of the design. The rollover strength of the bus is secured by ring structures positioned along the chassis, superseding the pillar type of design. Basic requests related to bus rollover safety are defined by UN/ECE Regulation No. 66. This regulation defines the minimum total energy that bus superstructure must absorb without violation of the residual space resulting from a rollover.
The main objectives of this paper are the design optimization of both the rollover ring structures and the modelling of finite rigidity links. To support the optimization we have created a database that contains information on types of links and structures used for ring design. This information is used for the analysis and design of bus superstructure in fast and cost-effective way. This approach allows for the design of bus superstructure in accordance to formal requirements, but using a small number of well-defined physical tests, minimizing the overall cost and time for the development.
The first part of this paper contains theoretical considerations, in which we have analyzed the process of bus rollover, and defined "plastic hinges" which are the ring zones where plastic deformations appear during rollover. The second part considers experiments for selection of appropriate cross-sections for rings of bus superstructure. We have shown that a small number of tests are sufficient for determining the shape and design or rollover rings that will absorb the minimum required level of impact energy. These tests are in accordance with the UN/ECE
Regulation No. 66, and have also been confirmed by analytic calculations. The third part of this paper describes the verification of bus superstructure by computational simulations. We have created a discretized model for calculation of stress states of rollover rings and for design of plastic hinges. These calculations take into account the effect of plastic hinges on mechanical behaviour of body segments as well as behaviour of the complete structure. We used dedicated software (KOMIPS) for computational simulations. The final verification of superstructure strength was accomplished by combining results of experiments and computational analysis. The results obtained by these two approaches are in agreement and together they verify the resultant bus superstucture. Finally, we discuss the expansion of database and methods for determining optimized solutions for specific requests.