View Q&A

WisDOT is looking to add two bridge parapet designs to our inventory.  The railing are from New York two and four rail parapets found in

<<

http://guides.roadsafellc.com/Documents/SBB29d/OtherDocs/404531-NY-2-4RailBridgeRail.pdf >>

One of the issue that we are having is trying to adapt MGS to thrie beam transition to these alternatives.  Our regular connection plates does not line up correctly.

Could we install a larger plate to allow for proper connection?

It is reasonable to expect that a plate used to connect thrie beam to a steel tube bridge rail may have to be altered for various bridge rail designs (especially the bolt hole locations to attach to the steel tubes).  However, we would not recommend enlarging the plate to cover all of the steel tube rails.  This would create unwanted snagging points for reverse direction impacts.  Instead, any bridge rail components located at heights above or below the thrie beam should be safely flared back away from traffic and/or possibly down to connect to an adjacent tube rail that does go behind the thrie beam rail.

A good reference for this type of connection can be found in a recent TTI test report titled "MASH TL-3 Testing and Evaluation of the TxDOT T131RC Bridge Rail Transition" and dated March of 2013.  It can be found on TTI's web site.  This document provides details for a MASH TL-3 crash tested thrie beam transition and connection to a 2 tube, steel bridge rail.  I believe the NY systems you are looking into are similar to this tested system.  Again, the top and bottom rail of the 4-tube configuration would need to be flared to prevent snag and tire interactions.