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The concept and product that was tested is a novel, low cost, lightweight replaceable energy absorption system that can be incorporated into modern rail transit vehicles to provide substantial protection in collisions with other trains and with road vehicles at grade crossings. The system is based on the sleeved column technology, in which one or more small-diameter steel core rods carry load, compress and efficiently absorb energy within a sleeve made of mild steel or other material. The sleeve prevents buckling of the relatively slender core and can be an existing structural member in the rail vehicle underframe.
Project Results
A detailed design of a sleeved-column energy absorber was developed and fabricated for dynamic testing. The sleeve is a rectangular, hollow, mild steel member with a length of nearly 8 ft. Rectangular structural members are more commonly used in rail vehicle construction than shapes with circular cross sections. A single core element was fabricated from a solid, high-strength, low-alloy steel piece.
Tests indicated that the design crush load is reached at the first stage of crush and then increases by a factor of two for the second stage crush, resulting in a desirable stepped load-crush response distributing energy absorption to other vehicles. Tests were performed and results reviewed by the project panel.
Figure 1
Sleeved column concept.
Product Transfer
While the primary objective of this project was to demonstrate the applicability of the sleeved-column technology to rail transit vehicles, the investigators also explored the incorporation of the system into light rail vehicles through a collaborative effort with a manufacturer of transit vehicles for U.S. service.
This project included generation of a structural layout of the new energy-absorbing elements in a representative light rail vehicle underframe and analytical evaluation of the performance of this system. This engineering work is available for potential use. The final report for this project was completed. It includes information needed by practitioners in the rail vehicle industry to design sleeved column energy absorbers.
The final report for this IDEA project can be found at:
https://www.trb.org/studies/idea/finalreports/transit/Transit22_Final_Report.pdf.
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