Patent ID: 6398192
Filing Date: 2002-06-04
Classification: E01F,Y10S

Abstract:
A breakaway support post for mounting a guardrail thereon as part of a highway guardrail system, comprising:an elongated body having an upper portion including a first upper end and a first lower end, and a lower portion including a second upper end and a second lower end, the second lower end having a configuration for installation adjacent to a roadway, and the first lower end having a first substantially vertical surface thereon and the second upper end having a second substantially vertical surface thereon; a first means for attaching a guardrail to the elongated body adjacent to the first upper end; a second means for rotatably coupling the upper and the lower portions and for releasably securing the upper portion of the elongated body generally aligned with the lower portion of the elongated body, wherein the breakaway support post is for resisting a rail face impact with a guardrail is attached to the support post and wherein an impact with one end of a guardrail system incorporating the support post will tend to rotate the upper portion of the elongated body relative to the lower portion of the elongated body; wherein the second means includes a first plate having a first opening and a second opening therethrough, and a third substantially vertical surface thereon, a portion of the third substantially vertical surface being disposed against a portion of the first substantially vertical surface, and the first plate being secured to the first lower end by a weld; a second plate having a third opening and a fourth opening therethrough, and a fourth substantially vertical surface thereon, a portion of the fourth substantially vertical surface being disposed against a portion of the second substantially vertical surface, the second plate being secured to the second upper end by a weld, the second plate being disposed adjacent to the first plate so that the first opening is aligned with the third opening, and the second opening is aligned with the fourth opening; a pivot pin portion extending through the first and the third openings, the upper portion of the elongated body being rotatable about the pivot pin portion relative to the lower portion of the elongated body; a shear pin having a shear pin portion extending through the second and the fourth openings, the shear pin portion being adapted to shear in response to a force to allow pivotal movement of the upper portion relative to the lower portion around the pivot pin portion, the pivot pin portion and the shear pin portion extending in a strong direction approximately perpendicular to the plates, wherein the support post exhibits a high mechanical strength in the strong direction, there being a weak direction generally perpendicular to the strong direction, wherein the support post exhibits a low mechanical strength in the weak direction; and the first and second plates each have a first edge and a second edge, the first edge facing generally toward the weak direction, and the second edge facing generally away from the weak direction, wherein the first plate further includes a chamfer disposed between a bottom edge thereof and a lower portion of the second edge thereof, and wherein the second plate further includes a chamfer disposed between a top edge thereof and an upper portion of the second edge thereof, the chamfers being positioned so that the first plate does not engage the lower portion and the second plate does not engage the upper portion when the upper portion of the elongated body rotates relative to the lower portion of the elongated body.