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I received this email from our Cleveland district - and a colleague has a good question about the inevitable PCB gap we seem to have after a couple of barrier moves caused by construction phases.

The overlapping method is the method done the most here in Ohio, but I worry about the ends not being anchored.   Personally, I've never seen the "shoe" but if it was sufficiently secured to the PCB without any potential snag points on the traffic side, it might be the better solution.

What is your insight on a better way to handle this recurring construction problem?

Email Received:

 Question on PCB.

When the contractor is switching phases he generally just moves  the PCB run over several ft.  He does not load it on a truck and place each piece.

The problem is the runs don't  come out the same and there are gaps.

It seems like every contractor has a method to handle the gaps.

Here are two such methods.

1.  Places a steel plate over the gap,  see attachment.
2.  over lap the PCB.

Question is which one do you think is safer?

Historically, we have recommended the overlapping method in situations where TCBs are to be placed in front of a rigid end of a concrete parapet. This recommendation was given prior to the development of several in-line attachments between freestanding and permanent concrete barriers. For the overlapped option, we stated to use 8 barrier sections beyond the end of the permanent barrier with a 2-ft gap between the freestanding and permanent barriers in order to reduce the propensity for vehicle pocketing and snag on the upstream barrier end. For overlapping TCBs, it would seem reasonable to use an overlap of at least 8 or 9 barrier segments for each run " front and back. However, I believe that the gap between both barrier runs could be reduced to 6 to 12 in. or so due to both barrier systems being freestanding, thus reducing the propensity for vehicle snag/pocketing. If limited space exists at the roadside edge for the overlapped option, one may consider the slight flaring of the rearward (shielded) TCB system in order to save space near the shoulder.

You noted another alternative where large steel shoes are placed over the gap produced when two barrier cannot connect to one another in line. For this system, it would be important for the shoe to not cause the vehicle to snag on raised components " screw handles, plates edges, or other structural features. Also, it would be important for the shoe to be able to transfer the necessary loads to allow the TCB system to perform in a safe manner, thus capable of transferring tensile, shear, and/or bending loads across the joint. However, it may be preferred to have tensile capacity in this type of connection using anchors into the barrier. KsDOT bridge engineers explored this option for bolted down, F-shape sections where a gap was needed in the TCBs. There may be other considerations when the shoe system is used for freestanding applications that have not yet come to mind. However, you may want to contact Rod Lacy and Scott King in Kansas to explore their current attachment and anchorage options. Other options may include using nested thrie beam on the front and rear faces, and combinations of other steel elements, and anchored into the TCB faces using common anchors. Gap lengths would need to be considered in the design and limited to a specified range. Finally, one could develop an adjustable F-shape section that could fit between barrier ends and serve to transfer the necessary loads across the gap.