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Repair of posts embedded in concrete

Question
State	OH
Description Text	We have several old existing bridge terminal assemblies on low volume roads which use posts embedded in concrete. When a single post is damaged and requires repair, our maintenance crews pull the old concrete, set a new post and then pour new concrete. They would like to eliminate the concrete work. Would a single post not set in concrete cause a performance problem? Are there other post depth or thickness options that would perform in a similar fashion to the embedded concrete post?

Question

State

Description Text

We have several old existing bridge terminal assemblies on low volume roads which use posts embedded in concrete. When a single post is damaged and requires repair, our maintenance crews pull the old concrete, set a new post and then pour new concrete. They would like to eliminate the concrete work. Would a single post not set in concrete cause a performance problem? Are there other post depth or thickness options that would perform in a similar fashion to the embedded concrete post?

System Performance Evaluation

System Types
Approach Guardrail Transitions (AGTs)

Applications

System Features

Date June 27, 2016
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Attachment gr-3b Bridge Terminal Assemblies 72-85.pdf

Response
Response (active)	To answer your question, changing from a post embedded in concrete to a post embedded into soil only could certainly change the performance of the system. To counter the loss of stiffness when removing the concrete, you would have to increase the post size and/or increase the embedment depth of the post. Unfortunately, I do not have any data on the strength and resistance capacity of these posts embedded in concrete. Consequently, we don't have a target strength/resistance to shoot for when designing a retrofit for these posts. Additionally, the strength provided by a W6x15 steel post will be significantly different than that of a 6"x8" wood post. So, I'm not really sure were to even start with a retrofit post. After a quick literature search, I cannot find any documentation on the development, analysis, or testing of these guardrail-to-bridge rail transitions. In comparing them to the transitions that have eligibility letters from FHWA, I have concerns about the crashworthiness of these systems to either MASH or NCHRP Report 350 safety standards. As such, I would not recommend new installations utilize these designs. Taking it a step further, if you have to repair one of these transitions, it may be easier to just tear out all of these concrete embedded posts and install a new NCHRP 350 approved transition system (one that doesn't include concrete posts). Transitions that the FHWA had previously noted as meeting NCHRP 350 criteria can be found on their website - in the acceptance letters and two Technical Advisory Memos. See the following links: http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/ http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/techadvs/archive/t504026/ http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/techadvs/archive/t504034/

Response

Response
(active)

To answer your question, changing from a post embedded in concrete to a post embedded into soil only could certainly change the performance of the system. To counter the loss of stiffness when removing the concrete, you would have to increase the post size and/or increase the embedment depth of the post. Unfortunately, I do not have any data on the strength and resistance capacity of these posts embedded in concrete. Consequently, we don't have a target strength/resistance to shoot for when designing a retrofit for these posts. Additionally, the strength provided by a W6x15 steel post will be significantly different than that of a 6"x8" wood post. So, I'm not really sure were to even start with a retrofit post.

After a quick literature search, I cannot find any documentation on the development, analysis, or testing of these guardrail-to-bridge rail transitions. In comparing them to the transitions that have eligibility letters from FHWA, I have concerns about the crashworthiness of these systems to either MASH or NCHRP Report 350 safety standards. As such, I would not recommend new installations utilize these designs. Taking it a step further, if you have to repair one of these transitions, it may be easier to just tear out all of these concrete embedded posts and install a new NCHRP 350 approved transition system (one that doesn't include concrete posts). Transitions that the FHWA had previously noted as meeting NCHRP 350 criteria can be found on their website - in the acceptance letters and two Technical Advisory Memos. See the following links:

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/techadvs/archive/t504026/

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/techadvs/archive/t504034/

Date June 29, 2016
Previous Views (75) Favorites (0)