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I need to show on my standards the minimum number of KTB's required for each type of crash tested installation.  Disregarding end treatments (crash cushions, end flares, etc.), in order to get the expected performance seen in the crash tests, how many barrier units would be required for:

1.  Freestanding installations (I seem to recall we talked about 9 units for transitions)

2.  Bolted down installations

3.  Staked down installations

4.  Back filled installations

I also need to know how many barrier units are needed for each installation type when used in combinations and transitions:

1.  Freestanding to bolted or staked down

2.  Freestanding to back filled

3.  Bolted down to staked down (no transition required?)

I recognize that we won't know some of these numbers for certain until after the transition crash test is conducted.

Using these numbers, I'll develop some drawings showing transitions along with alignment and length of need requirements for both approach and trailing ends.  This could get really messy when considering transitioning from say freestanding to bolted down and back to freestanding again.  An example could be along a short bridge where we can only bolt down three or four barrier units and then must transition to staked or freestanding units.  The three or four bolted down units would not be enough if that's all that was there but when used in combination with the transition or freestanding units at each end, the combination may be okay.  See my problem?

I'll put together some drawings that show some expected real world configurations and try and work out how it will all look.  It will be after the first of the year before I get to it though.

You ask some good questions about the number of barriers required for various barrier installations. Let me preface our discussion by stating that this issue has never been fully addressed through research. Impacts upstream of the length-of need (LON) have not been tested to date. The barriers have traditionally been tested in a certain configuration with a certain number of barriers upstream of the beginning of the LON. Therefore, the numbers I am recommending for the installations you asked about are estimates of the number of barriers upstream of the beginning of LON based on engineering judgment by MwRSF.

Let's tackle the first four installations first, remembering that we are disregarding end treatments.

1.   Free-standing barrier installations

- As I stated above, studies of impacts prior to the LON have not been studied at this time. All testing of the free-standing PCB designs has used 7-8 segments upstream of the beginning of the LON. For testing of the MwRSF F-shape barrier, there were approximately 7.5 barriers upstream of the beginning of the LON. Based on these successful crash tests, MwRSF would recommend a minimum of 7.5 F-shape barrier segments upstream of the beginning of the LON.

2.  Bolted down installations

- The discussion of the bolted tie-down barriers follows a similar argument. Again, no studies of impacts prior to the LON have been conducted for these types of barrier systems. In reviewing our bolted tie-down test (test no. KTB-1), it was observed that we had movement of 4 of the barriers in the impact region. Based on this movement and the lack of further testing, we believe it would be prudent to use 2.5 bolted tie-down barriers upstream of the beginning of the LON. This number of bolted down barriers would provide for the deflected barrier segments and an additional barrier for upstream anchorage.

3.  Staked down installations

- The staked down installation would require 2.5 tie-down barriers upstream of the beginning of the LON as well. Review of the full-scale testing (test no. FTB-1) showed deflection of 4 barrier sections. This number of bolted down barriers would provide for the deflected barrier segments and an additional barrier for upstream anchorage.

4.  Back filled installations

- We do not have any test data on back-filled temporary concrete barriers. However, it seems reasonable to assume that this type of installation will perform similarly to the bolted tie-down system. As such, we are recommending 2.5 tie-down barriers upstream of the beginning of the LON for this installation.

You also asked about some transitions and barrier combinations. As stated above, it is very difficult to give an accurate answer to these questions without further testing, but we have made some recommendations below.

1.  Freestanding to bolted or staked down

- For a free-standing barrier installation to a bolted or staked down installation, we would recommend the transition design currently under development here at MwRSF. This transition calls for 13 free-standing barriers attached to 4 transition barriers prior to attachment to the bolted or staked tie-down barrier or a rigid barrier. A schematic of this installation is attached. This would make for total of 17 barriers leading up to the bolted/staked or rigid barrier.

2.  Freestanding to back filled

- The same type of transition and number of barriers would be required for a free-standing to back-filled installation as the freestanding to bolted or staked down described in no. 1.

3.  Bolted down to staked down (no transition required?)

- For an installation of staked tie-down transitioning to bolted tie-down, the transition described above would not be necessary. The only transition needed for this installation would be to install the 12'-6" thrie beam sections across the joint between the staked and bolted barriers as shown in the figures of the full transition design. The use of the thrie beam should prevent rotation of the joint between the differing sections. This may not be necessary, but without further testing or evaluation, we feel we need to be conservative in our recommendations.

I hope this guidance helps answer some of your questions and gives you a start on your standards. These recommendation are our best engineering judgment at this time and could change based on future test results. Again, this is an area that really needs to be further studied through research to give the states better guidelines. The best solution to these issues would be the development of effective termination and end anchorage for temporary concrete barriers. However, that work has been proposed in the past and has not found a champion.