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-plane 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 post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the 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; and    a rod member extending laterally 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 the material of the splice connection which surrounds said axial portion of the rod member has a thickness t and a plate yield strength σ y , and the rod member has a diameter d b  and an ultimate strength σ u , each selected to satisfy the general relationship:                  πσ   u     ⁢     d   b   2         4   ⁢     3         ≥       σ   y     ⁡     (       t   ⁢           ⁢     d   b       +       4   ⁢     t   2         3         )               such that the 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 the edge distance extending from the outside edge of the material undergoing tear-out to the edge of the hole in said material is more than 1.5 times the diameter of the rod member.  
   
   
       3 . The post of  claim 1  or  2  wherein the rod member includes a distal end for receiving a fastener, the distal end being oriented away from the anticipated direction of a lateral impact.  
   
   
       4 . An energy absorbing post for roadside safety devices comprising: 
 a lower post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned; and    a means for attaching the lower post section to the upper post section and facilitating out-of-plane deformation in the post upon the impact of an errant vehicle on the upper post section;    such that at least a portion of the energy of the errant vehicle is absorbed by the out-of-plane deformation.    
   
   
       5 . The post of  claim 4  wherein the means for attaching comprises a splice connection between the lower and upper post sections to facilitate out-of-plane deformation in the material of the splice connection.  
   
   
       6 . The post of  claim 5  wherein: 
 the means for attaching comprises a rod member extending laterally through a hole in the splice connection, wherein the rod member closes at least one portion of the splice connection without opposing compressive fasteners; and    the edge distance extending from an outside edge of the material undergoing tear-out to the hole in said material is more than  1 . 5  times the diameter of the rod member.    
   
   
       7 . The post of  claim 6  further including a stress concentrator located at the edge of the hole.  
   
   
       8 . The post of  claim 6  further including a pre-buckle formed in the edge of the hole.  
   
   
       9 . The post of  claim 6  further including a stress concentrator and a pre-buckle located at the edge of the hole.  
   
   
       10 . The post of  claim 6  wherein the rod member includes a distal end for receiving a fastener oriented away from the anticipated direction of a lateral impact.  
   
   
       11 . 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 in the anticipated direction of a lateral impact.  
   
   
       12 . The post of  claim 5  wherein the means for attaching comprises overlapping plates connected by a bolt, wherein the axial distance between the bolt head and nut substantially exceeds the thickness of the overlapping plates, such that angular deflection of the bolt during an impact facilitates out-of-plane deformation in one or more of the plates.  
   
   
       13 . The post of  claim 12  further including a compressible gasket positioned between the plates and the bolt head or nut.  
   
   
       14 . The post of  claim 6  wherein the rod is a single rod member such that the upper post section pivots on the rod member during an end on impact.  
   
   
       15 . The post of  claim 14  including a splice fastener positioned upstream from the rod member, wherein the edge distance for the upstream fastener is less than  1 . 5  times the diameter of the upstream fastener.  
   
   
       16 . The post of  claim 4  wherein the means for attaching comprises: 
 a splice plate oriented in the direction of a lateral impact; and    a tab extending from the splice plate and connected to the post such that impact energy may be absorbed by out-of-plane tearing in the area where tab extends from the splice plate.    
   
   
       17 . The post of  claim 4  wherein the means for attaching comprises: 
 a generally horizontal slot formed in a lateral portion of the post, the lateral portion facing the anticipated direction of impact; and    a splice plate rigidly connected near said slot such that impact energy may be absorbed by out-of-plane tearing in the lateral portion of the post.    
   
   
       18 . The post of  claim 17  further including one or more generally vertical slots adjacent to the generally horizontal slot, the generally vertical slots further facilitating out-of-plane tearing in the lateral portion of the post.  
   
   
       19 . The post of  claim 17  or  18  further including a spacer located between the splice plate and the post to further facilitate out-of-plane tearing.  
   
   
       20 . The post of  claim 4  wherein the means for attaching comprises a splice plate attached on a first planar side thereof to the upper or lower post section, the splice plate including a bent over portion welded on an opposing planar side to the other of the upper or lower post section, such that impact energy may be absorbed by out-of-plane loading of the weld material.  
   
   
       21 . The post of  claim 20  further including a spacer located between the splice plate and the post for further facilitating out-of-plane loading in the weld area.  
   
   
       22 . An energy absorbing post for roadside safety devices comprising: 
 a lower post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned;    a splice connection between the upper and lower posts sections, the splice connection including overlapping splice plates; and    a bolt connecting the overlapping splice plates, wherein the bolt forms an axial gap between the bolt head and nut, the gap exceeding the thickness of the overlapping splice plates;    wherein the axial gap permits angular deflection of the bolt during an impact to facilitate tear-out in one or more of the overlapping splice plates and thereby absorb at least a portion of the energy of an errant vehicle impacting the upper post section.    
   
   
       23 . The post of  claim 22  further including a compressible gasket positioned in the axial gap.  
   
   
       24 . An energy absorbing post for roadside safety devices comprising: 
 a lower post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned;    a splice connection between the lower and upper post sections, the splice connection including a splice plate rigidly attached to one of the upper or lower post sections; and    a tab extending from a portion of the splice plate, the tab being attached to the other of the upper or lower post sections;    such that the tab closes the splice connection, and the energy of an errant vehicle impacting the upper post section is absorbed by out-of-plane tearing in the material of the splice plate near where the tab extends therefrom.    
   
   
       25 . The post of  claim 24  wherein the splice plate is oriented facing the anticipated direction of a lateral impact.  
   
   
       26 . The post of  claim 25  wherein the tab is cut out from the material of the splice plate.  
   
   
       27 . The post of  claim 24  or  25  wherein the tab is welded to the upper or lower post section.  
   
   
       28 . An energy absorbing post for roadside safety devices comprising: 
 a lower post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned;    a splice connection between the lower and upper post sections, the splice connection including a splice plate facing a lateral impact and attached to the upper or lower post section; and    a generally horizontal slot formed in a portion of the other of the upper or lower post sections, the splice plate being rigidly attached to the post near said slot;    such the energy of an errant vehicle impacting the upper post section is absorbed by out-of-plane tearing in the material of the upper or lower post section near said slot.    
   
   
       29 . The post of  claim 28  wherein the splice plate is welded to the upper or lower post section near the generally horizontal slot.  
   
   
       30 . The post of  claim 28  or  29  further including one or more generally vertical slots adjacent to the generally horizontal slot, the generally vertical slots further facilitating out-of-plane tearing in the post.  
   
   
       31 . The post of  claim 28  or  29  further including a spacer located between the splice plate and the post to further facilitate out-of-plane tearing in the post.  
   
   
       32 . The post of  claim 29  further including: 
 one or more generally vertical slots adjacent to the generally horizontal slot; and    a spacer positioned between the splice plate and the post,    wherein the generally vertical slots and spacer further facilitate out-of-plane tearing in the post.    
   
   
       33 . An energy absorbing post for roadside safety devices comprising: 
 a lower post section for engaging a foundation upon which the roadside safety device is mounted;    an upper post section for receiving the impact of an errant vehicle, the upper post section and the lower post section being generally vertically aligned;    a splice connection between the lower and upper post sections, the splice connection including a splice plate facing a lateral impact;    a first portion of the splice plate is rigidly attached on a first planar side to the upper or lower post section; and    a second portion of the splice plate is side bent over and an opposing second planar side thereof is welded to the other of the upper or lower post sections;    such that impact energy of an errant vehicle is absorbed by out-of-plane tearing in the weld area.    
   
   
       34 . The post of  claim 33  wherein the welding includes one or more generally vertical welds.  
   
   
       35 . The post of  claim 33  or  34  further including a spacer located between the splice plate and the post to further facilitate out-of-plane tearing in the weld area.