Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Brandon]

I have noticed throughout the years, that thrie beam guardrail seems to be fairly rare outside of Michigan.  MDOT tends to use a lot of it while most of the DOTs tend to use it only prior to bridges to attach W-rail to a concrete barrier.  Prior to installing thrie beam, MDOT used to use two overlapping W-rails.

Is there a reason for this?

[agentsteel53]

where did the spelling "thrie" come from?  I thought first it was a proper noun, but it looks to just be a bastardization of the word "three", whose origin is visually obvious.

[Big John]

Thrie beam is usually used in transitions from the less stiff W-beam guard rail to the solid concrete barrier.   Being it is stiffer than the W-beam to make a better transitionbetween those 2 barriers to make a crash less severe.  Cost is a factor in why most states use the W-beam instead of thrie beam except in transitional areas.

[cbeach40]

According to one of the first results I found, the deflection of Thriebeam is about 0.6 m. MTO uses 0.9 m for traditional W-rail, and 0.3 m with a channel. So it's kind of a thin margin that Thriebeam falls in between a standard rail and a fitting it with a channel.

Segment of rail both with and without channel:
http://goo.gl/maps/UusjR

The other advantage of using Thriebeam is the increased surface area, which helps in areas with significant heavy vehicle volumes.

I can't speak for other jurisdictions, for retrofits, MTO will tend to go with the channelized rail. For new build, MTO handles it in their typical overkill fashion:
http://goo.gl/maps/YdQly

[Brandon]

For a contrast, here's a typical MDOT installation:

https://maps.google.com/maps?hl=en&ll=42.305213,-84.994601&spn=0.002305,0.005284&t=h&z=18&layer=c&cbll=42.305053,-84.995655&panoid=TOlCgfINOAg8NKV1RXyR1g&cbp=12,192.28,,0,10.58

[briantroutman]

Everything you ever wanted to know about thrie beam guardrail is in this video from the FHWA:(https://archive.org/details/gov.dot.fhwa.ttp.vh-2b)

Thrie is apparently just an archaic (Old Saxon) version of “three”, but why it’s used in this specific case is beyond me. If you search “thrie” in Google most of the first page results are related to the guardrail.

[mass_citizen]

thrie beam is the standard for all median guardrail (where concrete is not used) in Massachusetts

[Alps]

NJDOT does not use Thrie in any application. I believe NYSDOT and/or NYSTA are fully accepting, on the other hand (though box beam prevails in most occurrences).

[Tom958]

Everything you ever wanted to know about thrie beam guardrail is in this video from the FHWA:(https://archive.org/details/gov.dot.fhwa.ttp.vh-2b)

Wow, I'm converted.

Has anyone investigated the feasibility of retrofitting thrie beams to existing W beam installations? Perhaps with a steel sleeve that fits snugly over the existing shorter posts? I'm thinking there are several hundred miles of W beam median barrier in Georgia alone that really should be thrie beam instead if it wasn't cripplingly expensive to retrofit.

[jeffandnicole]

NJDOT does not use Thrie in any application.

Sure they do.  Where I-295 was reconstructed from Exits 45 to 57 several years ago, Thrie was used the entire length within the median.  http://goo.gl/maps/9kZzq  You can clearly see the different between the W (used on the far shoulder) & the Thrie.

Another example on NJ 29 between 195 & the Trenton Tunnel, when guiderail was either added or upgraded from existing W: http://goo.gl/maps/YkbXS

In their engineering documents online, the use of Thrie guiderail is mentioned here (Section 8.4.1 Part C): http://www.state.nj.us/transportation/eng/documents/RDM/sec8.shtm#warrantsmedbar

[Tom958]

I just saw a crew installing a new non-modified thrie beam guardrail on I-85 near Atlanta. I'm pist. Shouldn't I be?

[cpzilliacus]

I have noticed throughout the years, that thrie beam guardrail seems to be fairly rare outside of Michigan.  MDOT tends to use a lot of it while most of the DOTs tend to use it only prior to bridges to attach W-rail to a concrete barrier.  Prior to installing thrie beam, MDOT used to use two overlapping W-rails.

Is there a reason for this?

Maryland uses them mostly for those transitions from "W" rails to Jersey-style concrete barriers.
 
Only place I know of with thrie beam guardrail is on I-270 Southbound in Rockville, Montgomery County.

[cl94]

It's rarely used in New York except in a few cases near bridge piers, impact attenuators and other locations. Box beam guide rail serves a nearly-identical purpose and is much more common, likely because less metal is required to achieve a similar moment of inertia.