Guard Rail Strong or Weak Posts 1

[nwong]

Greetings

Guardrails are often labeled as Strong or Weak post but I can't find a definitive definition of each. I have heard it deals with the deflection of the post at impact but can't find the criteria or the standard that caterogizes the system as strong or weak.

Your help would be greatly appreciated.

Nicholas

 

[TTK]

try to get your hands on a copy of the AASHTO Roadside Design Guide, this has a complete discussion of guardrail systems.

weak posts are extrememly small and their only purpose is to hold the rail element up at the proper elevation to re-direct traffic upon impact. The posts will easily shear off during impact.

Strong posts may also break during impact but they are designed to take some of the impact force in shear and bending, and they may just undergo plastic deformation during low speed impacts.