Finite element modeling and side impact study of a low-floor mass transit bus

Abstract

Mass transportation systems, specifically bus systems, are a key element of the national transportation network. Buses are one of the safest forms of transportation; nonetheless, bus crashes resulting in occupant injuries and fatalities do occur. According to Traffic Safety Facts reports from 1999 to 2003, an average of 40 fatalities and 18,430 injuries of bus occupants have occurred per year, with side impact accounting for 14 % according to type of impact and by initial point of impact it accounts for 36%. A full scale crash test is considered the most reliable source of information regarding structural integrity and safety of motor vehicles. However, the high cost of such tests and difficulties in collecting data has resulted in an increasing interest in the analytical and computational methods of evaluation. With the advancement in computer simulations, full finite element validated vehicle models are being analyzed for different impact scenarios to predict vehicle behavior and occupant response. This thesis research work presents the procedure for development of a finite element (FE) model of a mass transit bus and the results of its crashworthiness and structural integrity analysis. The finite element model is developed by extracting mid-surface from solid cad model. This model is a detailed model with all parts. All parts are connected using different multi point constraints and special links with failure to model actual types of structural connections such as bolts and spot welds. LS-DYNA non-linear, explicit, 3-D, dynamic FE computer code was used to simulate behavior of the transit bus under different side impact scenarios. A parametric study is done to study structural response of transit bus when impacted by vehicles of different masses, sizes and shapes. A multibody analysis is done to study occupant response to different side impact crash conditions.