Journal of Public Transportation Article in Volume 8, Issue 4 Special Edition: Safety and Security (2005) by Andrzej Morka, Lesław Kwaśniewski, Jerry W. Wekezer
The main objective of this study was to assess usefulness of 3-D, nonlinear dynamic, explicit computer codes for transit safety and security research. An analysis of response of a paratransit bus structure under loading caused by high explosive (HE) detonation is presented. It was assumed that the cubic HE charge detonates in the air near the bus. The ground was modeled as a rigid stationary wall. The problem was studied using LS DYNA, an explicit, 3-D, dynamic, nonlinear finite element program. The HE detonation and the processes of shock propagation in the air were modeled using the mesh with the Euler’s formulation. The Euler’s mesh was modeled as a rectangular prism sufficiently large enough to cover the entire bus structure. The nonreflecting boundary conditions on the top and side surfaces of the Euler’s domain and the sliding interface on the bottom side for the contact with the ground were assumed.
A finite element model of the Ford Eldorado Aerotech 240paratransit bus was developed for this study. This model consisted of 73,600 finite elements and had 174 defined properties (groups of elements with the same features) and 23 material models. Computational analysis provided useful information about dynamic deformations and damage inflicted to the bus structure under load blast wave activated by the HE detonation. It allowed for detailed, rigorous analyses of time histories of accelerations, velocities, deformations, and stresses. Resulting acceleration and overpressure histories were correlated with expected blast injuries of the bus passengers. The data obtained can be used to improve passenger safety and to reduce the threat of suicidal terrorist attacks against public transit. Changes in the bus structure and replacement of some materials to build a safer class of vehicles can be carefully considered and implemented. View the full article or the entire Journal issue.