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Long Span and Short-Radius Guardrail

Question
State OH
Description Text

Yet another question for the MWRSF's designed Ohio Long Span guardrail design. Previously, I asked about increasing the length of the span and about its interaction with a curbed drainage inlet.

Can any portion of the TL-3 long span be installed on a radius?


Ohio, maybe more than the other Midwest Pooled Fund states, have lots of driveways and side roads directly next to streams. As other states do, Ohio uses the radius guardrail to transition to the side road/driveway.

For example, eastern states property frontages are narrow, and this fact usually places driveway access right in the middle of the LON of a guardrail run off of a bridge or culvert.
T
he short radius rail
needed. But on the Ohio Long Span design, the system is 100 feet long, meaning 37.5 feet of nested rail is placed in advance of the actual long span portion. Can any portion of this rail be radiused?



I am hoping the last 25 feet (outside of the CRT post area) can be, but I am afraid I know the answer you'll give.

As usual, I appreciate your insight on this.
Keywords
  • Guardrail
Other Keywords none
Date November 8, 2005


Response
Response

The crash testing of the long-span guardrail system was conducted with the entire system installed parallel to the roadway, including the nested and non-nested guardrail segments as well as both anchors. Without further testing, it is difficult to allow or recommend the use of a curve or radius within the upstream or downstream segments of the nested W-beam guardrail adjacent to the long span since a curved or radiused rail could affect the system's overall safety performance near the long-span region due to a change in tensile capacity.

 

As noted above and at this time, we cannot recommend the use of a radius within the nested guardrail length of 37.5 ft. After that distance, it may be possible to begin the short radius guardrail design which consists of a straight thrie beam guardrail section prior to reaching the curved thrie beam section. A transition region would be needed between the thrie beam section and the W-beam section. Using the existing long-span and short radius guardrail configurations, the culvert would need to be a minimum specified distance away from the curved thrie beam section (and intersecting road or drive) based on the geometry of the two current barrier systems. If the primary side of the short radius guardrail did not attach to a bridge rail (as currently being developed), there may be some possibility to shorten the required thrie beam length downstream of the curved thrie beam segment from that currently used.

Date November 23, 2005


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