Energy absorbing post for roadside safety devices

Abstract

An energy-absorbing post for absorbing the impact energy of an errant vehicle wherein the impact energy is absorbed by out-of-place deformation in the material of the post. Out-of-plane deformation is provided by utilizing a through bolt extending through a splice connection between upper and lower posts sections. Alternatively, out-of-plane deformation is provided by leaving an axial gap on a splice bolts. For terminal applications, a single through-bolt is utilized to allow the upper post section to pivot during end on impacts. Bolt tear out facilitators, including stress concentrators and pre-buckles, or an angled through-bolt decrease any initially high tear-out forces. Direct out-of-plane deformation is provided by extending a tab from a splice plate and connecting the tab to the post, by forming one or more slots in an upstream lateral face of the post and directly welding a splice plate near the slots, or by connecting a bent over splice plate on opposing planar sides thereof to facilitate out-of-plane deformation in a weldment area between the plate and the post.

1 . An energy absorbing post for roadside safety devices comprising:
 a lower and an upper post section, each having opposing front and rear lateral, spaced apart, generally parallel flanges interconnected by a web section;   the lower post section for engaging a foundation upon which the roadside safety device is mounted;   the upper post section for receiving an impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned;   a splice connection formed between the lower and upper post sections, the splice connection having a splice plate rigidly attached to one of the upper or lower lateral flanges; and   a rod member extending laterally from a face surface at the front to a face surface at the rear of one of the upper or lower flanges and through holes in the splice connection, wherein the rod member includes at least one axial portion thereof that closes the splice connection without opposing compressive fasteners;   wherein material of the splice connection which surrounds said axial portion of the rod member has a thickness t and a plate yield strength σ γ , and the rod member has a diameter d b  and an ultimate strength σ u , each selected to satisfy the general relationship: such that energy of an errant vehicle impacting the upper post section may be absorbed by tear-out from the material of the splice connection.   
   
   
       2 . The post of  claim 1  wherein an edge distance extending from an outside edge of the material undergoing tear-out to an edge of one of the holes in the material of the splice connection is more than 1.5 times the diameter of the rod member. 
   
   
       3 . The post of  claim 1  wherein the rod member includes a distal end for receiving a fastener, the distal end being proximate the face surface at the rear of one of the upper or lower flanges. 
   
   
       4 . The post of  claim 2  further including a stress concentrator located at the edge of one of the holes. 
   
   
       5 . The post of  claim 2  further including a pre-buckle formed in the edge of one of the holes. 
   
   
       6 . The post of  claim 2  further including a stress concentrator and a pre-buckle located at the edge of the hole. 
   
   
       7 . The post of  claim 6  wherein the rod member is oriented at an acute angle with respect to the post in a vertical plane extending along the face surface at the front of one of the upper or lower flanges. 
   
   
       8 . The post of  claim 1  wherein the rod is a single rod member such that the upper post section pivots on the rod member during an end on impact to the roadside safety device. 
   
   
       9 . The post of claim  14  including a splice fastener positioned upstream from the rod member, wherein an edge distance for the upstream splice fastener is less than 1.5 times the diameter of the upstream fastener.