Rollover and roof crush analysis of low-floor mass transit bus

by Deshmukh, Pankaj S.

Today transit buses are an integral part of the national transportation system. According to National Transportation Statistics from 1990 to 2002, the number of transit motor buses in the U.S. has increased 30 percent. Although buses are one of the safest means of transportation, occupant injuries and fatalities in bus crashes do occur. Rollover strength has become an important issue for bus and coach manufacturers. Today European regulation “ECE-R66” is in force to prevent catastrophic rollover accidents. The Standard Bus Procurement Guidelines (SBPG) of the American Public Transit Association (APTA) also mentions the roof crush test for the assessment of bus superstructure and roof. This thesis discusses the development of a finite element (FE) model of a bus, and the analysis of its roof crush and rollover in LS-DYNA. The FE model was validated for the roof crush test carried according to the standard bus procurement guidelines (SBPG). ADAMS-View software was used to simulate the rollover of the bus. Bus accelerations, velocities, and its angle with the ground just before impact were measured in ADAMS and then used as input for the LS- DYNA analysis. According to the ECE-R66 regulation, a passenger’s survival space is defined in the bus model to check whether there is any intrusion into the survival space during or after the rollover. This ensures that the bus structure has sufficient strength to avoid intrusions into the survival space. The effect of passengers’ weight on energy absorbed by the bus structures during rollover is also discussed. Development of the MADYMO bus model and its rollover simulations were also included in this research. Dummy kinematics and injuries sustained during rollover for various seated and standing positions were studied as well. v