TR Circular E-C058_9th LRT Conference_2003.pdf - Florida ...

Sarunac and Zeolla 101
Comparison of the CEM Versus the 2-g Approach—Scenario 4.1
An additional scenario similar to Scenario 4 was analyzed using vehicles designed to the 2-g
approach. As previously noted, the 2-g strength ratio is based on the assumed weight of the LFE
and the existing vehicle. The results of this scenario were compared with Scenario 4 to determine
the differences between using CEM and the 2-g approach:
• In comparing the 2-g results with the CEM design, it can be seen that the CEM zones
limit the peak and average accelerations in passenger compartments significantly.
• The strength-based approach with a CEM zone was successful in limiting the loading
transferred to the LFE body because the acceleration levels are lower at the LFE.
• The strength-based approach with a CEM zone also reduces the acceleration levels in
the second vehicle in the train consist.
• The deformation is higher in the ends of the vehicle with CEM, although this is
expected. The intent of the CEM zone is to deform in a controlled manner (i.e., at a specific
force) over a predetermined distance.
• The second vehicle in both consists sustained structural damage, indicating higher
energy levels between coupled vehicles. This did not occur in the CEM case due to the lower
weight of the vehicles and the energy absorption at the impact interface.
• The deformation level in the LFE is very low for both the CEM and 2-g vehicle.
Hence, loss of occupied volume did not occur. However, the overall weight of vehicle with an
LFE and CEM is estimated to be less than the 2-g approach. This weight savings may be
significant when considering propulsion and braking requirements. Additionally, the lighter LFE
may have lower energy and maintenance costs.
To simplify the comparison, Table 2 shows only the maximum values for the deformation
and acceleration along the vehicles in the moving consist from Scenarios 4 and 4.1.
TABLE 2 Comparison of Results between the CEM and 2-g Approach for Collision
Scenarios 4 and 4.1 (2 vehicles into 2 vehicles at 15 mph)
1st Vehicle
2nd Vehicle
CEM 2-g CEM 2-g
Max. Deformation (in.)
Coupler 12 12 12 12
End Car Structure
(CEM or Under-frame)
28.4 11.3 0 1.3
LFE Structure
(Max. value at any end)
0.5 0.35 0.173 0.3
Accelerations Peak, g
End Cars 2.2 4.6 0.85 4.7
LFE 1.72 3.7 0.51 4.0
Accelerations Avg., g
End Cars 1.0 1.5 0.51 2.1
LFE 1.1 1.5 0.51 1.7