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I’ve been working on developing some KDOT guidelines for
TCSB condition inspection to help KDOT’s engineers in the field determine
whether or not to accept or reject TCSB on KDOT projects. The attached guidance
is based on information available from ATSSA/MwRSF/FHWA. Can you, or someone at
MwRSF, please review this and provide your thoughts/feedback as needed? It’s
only a few pages with pictures/bullet points so hopefully it won’t be too
onerous…

I looked through your document and think it looks pretty good in general. This is an issue for many states, and no formal research has been done to provide consistent guidance from state to state. We have proposed this in the past, but it has never received enough traction to get funded.

My main concern is that the guidance may not be detailed enough that someone will be able to clearly denote whether the barrier needs to be replaced or not. Of course you have no hard data to support that type of detail either, so it is a bit of a catch 22. However, things such as clarifying crack width and length, critical locations of damage, and other details may allow for easier determination of adequate barrier condition for use.

I have some other comments below.

1. Under the marginal TCSB guidance:
1. You note that the cracks should not propagate through the both sides of the barrier. You may want to be more stringent and note that superficial or surface cracks are preferred and that cracks should not extend more than ½ way through the section.
2. I would maybe note to limit the disengagement of concrete around the toes to less than a 3” triangular section in order to maintain the interlock of the barrier segments as they rotate when impacted. We believe that disengagement or loss of the toe section of the barrier can increased barrier deflection significantly.
3. I would not want to have any exposed rebar on a system due to concerns with the lack of effectiveness of the reinforcement without engagement of the concrete and corrosion.
2. In the Q&A section on the final page, there may be some concerns with having an unacceptable barrier on one face and acceptable on another. For example, if the toes are disengaged on the non-impact side face, there would still be concerns for increased barrier deflection. Similar concerns would exist for concrete damage near the loop connections.

Many other states have similar details. You may want to look at the attached files. One of them contains a summary of guidance from many states and may be useful to get a consensus on what guidance others have been using.

Let me know if that helps or if you need more information.