We have a project along an interstate where construction changes are causing us to place modified thrie-beam within the median. There are a few locations where a post will need to be dropped to accommodate a crossing box structure. Can you give any guidance for possibly dropping a post within a modified thrie beam run? Another item we would like to get your thoughts on is, where more than one post needs to be dropped, we are going to ask that they transition to an MGS long span system. For location that have the MGS long span within the median, guardrail will be placed along both sides of the median. Thank you
I have several thoughts about your median modified thrie beam installation issues.
Based on the points above, we would likely recommend the use of the culvert mounted posts if possible as they pose the fewest concerns/unknowns relative to the barrier performance. Of course, this has not been full-scale tested and evaluated at this time, but it would likely represent the best option without further research.
Note that the concept of median guardrail (W-beam or thrie beam) with an omitted post or as long span systems may make an interesting pooled fund program submission if you were interested in putting them forward. Other states may have similar needs or issues.
Bob, Thank you for the quick response. I did want to clarify one item. When I mentioned using a MGS long span within the thrie beam run, I meant that we would have a section of railing that transitioned from the thrie to the w-beam and then have a MGS w-beam long span (~150 ft) then transition back to thrie beam with a section of railing that transition from w-beam to thrie beam. Would you see a problem with that approach? And Yes I think I should submit a problem statement, thanks for the idea.
I think you could do that while following previous guidacne for transitioning between those systems.