Balancing Collision Forces in Crush / Energy Analysis
Balancing Collision Forces in Crush / Energy Analysis
by Nathan Shigemura and Andrew Rich
Crush/energy analysis continues to remain an important tool
for the reconstructionist. It provides another method of resolving a traffic
crash where other methods may not be available or appropriate. For any
reconstructionist who is faced with the task of performing this analysis, this
article may help take the mystery out of the process of solving for the
stiffness coefficients of a particular crash.
Mr. Shigemura and Mr. Rich show you how appropriate stiffness
coefficients can be determined by performing an analysis where collision forces
are balanced and new stiffness coefficients are calculated. These values can be
obtained when published values are not available or not applicable. By
determining the proper stiffness coefficient, you will be able to calculate
equivalent barrier speeds (EBS), delta-V’s and impact speeds of colliding
vehicles.
An appendix at the end of the article shows you an example of
the process of balancing collision forces and calculating new stiffness
coefficients for one vehicle, when the value is known for the other.
ABOUT THE AUTHORS:
Nathan Shigemura retired in 2002 as a sergeant from the Illinois State Police,
where his duties included crash investigation instructor, traffic crash
reconstructionist and supervisor of the statewide Traffic Crash Reconstruction
Unit. As co-owner of the Traffic Safety Group, LLC, a traffic crash
reconstruction and analysis company based in Illinois, he remains active as a
reconstructionist. Since 1989, Mr. Shigemura has been an adjunct faculty member
of IPTM, for whom he continues to teach courses nationwide in all levels of
traffic crash investigation and reconstruction. He is the author of
Mathematics for the Traffic Accident Investigator and Reconstrucitonists,
published by IPTM in 1996 and co-author with John Daily of Fundamentals of
Applied Physics for Traffic Accident Investigators, published by IPTM in
1997, and co-author with John Daily and Jeremy Daily of Fundamentals of
Traffic Crash Reconstruction, published by IPTM in 2006. Mr. Shigemura
received in 1975 a BS degree in Electrical and Electronic Engineering (BSEE)
from the University of Illinois, Chicago. He is accredited by the Accreditation
Commission for Traffic Accident Reconstruction (ACTAR).
Andrew Rich began his career in law enforcement in 1988 with the Palisades
Interstate Parkway Police (PIP) in Northeastern New Jersey. After seven years of
service, he was promoted to sergeant and became the officer in charge of the
Accident Investigation Unit and the Search and Rescue Unit. Additionally, he
programmed the department’s computer systems applications. He was also a
part-time investigator for the Bergen County (NJ) Prosecutor’s Office Fatal
Accident Investigation Unit (FAIU). In 1999 Sergeant Rich left the PIP to become
a detective for the Bergen County Prosecutor’s Office (FAIU), where he is
presently assigned to investigate and reconstruct serious and fatal collisions
on a county-wide basis. Andrew Rich is a member of IPTM’s adjunct faculty, is
ACTAR accredited, and is currently completing the last classes necessary for a
degree in mechanical engineering at the New Jersey Institute of Technology.
Specifications: 24 pages; 8-1/2”x11”; saddle stitched;
Publisher: IPTM (April 2008)
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