View Q&A

One of our major suppliers of guardrail components, Universal Industrial Supply out of Utah provide the asymmetric transition pieces as shown in the attached drawings.  As you can see, they have cut a thrie beam element and welded a rear flange to the bottom of the asymmetric section.  During development of the “transition to the transition,” I know Midwest was using a welding section and then found a manufacturer who could make stamped sections.  Is this welded section acceptable?  Are other states having problems getting the continuous stamped asymmetric section?

The asymmetric W-to-thrie beam transition piece shown in the attached photos corresponds to a design variation that was evaluated during the development of the MGS upstream stiffness transition for approach guardrail. In test no. MWT-4, a 2000P vehicle impacted upstream of this W-to-thrie beam transition piece at a speed of 98 .1 km/h (61.0 mph) and at an angle of 25.3 degrees. As the truck progressed into the guardrail during test no. MWT-4, vehicle redirection continued until the front bumper contacted the point of the flat plate extension on the bottom of the transition element. The start of the weldment proved to be a stress concentrator that produced a tear in the W -beam to thrie beam transition section. The tear quickly propagated through the entire segment and ruptured the rail system. Thereafter, all redirection stopped, and the test vehicle moved forward into the end of the stiff transition section where it was brought to an abrupt stop. Thus, this test showed that the current design was unsafe and should not be used on high-speed roadways.

http://mwrsf.unl.edu/researchhub/files/Report188/TRP-03-94-00.pdf     

Following test no. MWT-4, MwRSF designed a revised W-to-thrie beam transition piece that is recommended for use when creating approach guardrail transitions with the MGS. This design is attached and has been successfully crash tested to the MASH criteria.