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Background

The Bailey Bridge panel bridge system has been around since WWII. It has been credited as being one of the top 3 technological advancements that allowed the allies to win the war. After the war, the surplus of Bailey Bridge parts were sold off and distributed around the world. While these bridges were intended to be for temporary use (military temporary use and civilian temporary use are two different things), some of these old bridges can still be found in use today.

Bailey schematic Bailey Schematic with tapered transom

A quick search on google will return all sorts of beautiful modern bridges that are not Bailey Bridges. To me, a Bailey Bridge is a very specific type of panel bridge from WWII or post war sold by Bailey-Uniflote. However listening to colleagues, and even looking at the google search results, it appears that Bailey Bridge is just another word for Panel Bridge. Similar to Xerox and Photocopy, or Kleenex and tissues. So this has muddy some of my search efforts thus far.

The Problem

The problem I face is trying to determine which of the 4 (maybe more) types of panel bridge systems I may be looking at as they can be very similar in component layout at a quick glance and even some basic measurements.

So far my research has told me that some of the distinguishing factors for these panel type bridges are:

  • Panel size
  • Panel diagonal members (I, C, HSS/TUBE)
  • Deck width
  • Transom location
  • Transom size

Panel Size

The original Bailey Bridge had a panel length of 10'0" (3.048 mm) from centres of connecting pin holes and a height of 4'9" (1.448 mm) from centres of connecting pin holes. The overall height was 5'1". Anything outside of these dimension would indicate a newer panel system such as an Acrow 700xs or Mabey Compact 200 or the like.

Diagonal Members

In the Bailey Bridge panel there are two diamond shapes. The diagonals of these shapes were originally I sections. At some later time these sections changed to C-Channels and rumour has it HSS or tube sections were used by certain manufactures. Anyone have any confirmation on how to identify or rule out potential bridge type based diagonal section type? Maybe even some date ranges for the various section type?

Deck width

  • The original Bailey Bridge has a roadway width of _____ and a clear width between trusses of ____.
  • The standard widened Bailey Bridge has a roadway width of 10'9" (3.28 m) and a clear width between trusses of 14'3" (4.34 m).
  • The Extra Wide Bailey Bridge has a roadway width of 13'9" (4.19 m) and a clear width between trusses of 15'8" (4.77m).

I am not sure what the standard deck width is on an Acrow 300 or a Mabey 100.

Transom Location

On a Bailey Bridge, the transoms are located adjacent to the panel's end vertical and middle vertical. This can been seen in the following diagram and photo:

Bailey Transom Location Diagram

Bailey Single Transom Location Photo

If the transoms need to be double up to carry a heavier load then there are 4 transoms per bay. Two either side of the middle vertical and 1 inside of each end vertical as shown in the following photo:

Bailey Double Transom Location Photo

For an Acrow 300 style panel bridge, the transom is located at the base of panel's diamond as seen in the following photo:

Acrow 300 Bridge Transom Location

Mabey 100 transoms are located ?????

Transom Size

  • A standard Bailey Bridge has a transom length of 18'0" (5.49 m) with a constant 10" depth. There will be 3 holes near the bottom flange to allow for 3 panel lines.
  • A Standard Widened Bailey Bridge has a transom length of 19'11" (6.1 m) with a 12 in depth between under the deck and a 10" depth at the panel lines. There will be 4 holes near the bottom flange to allow for 4 panel lines.

Wide DD Bailey Transom

  • An Extra Wide Bailey Bridge has a transom length of 19'11" (6.1 m) with a 12 in depth between under the deck and a 10" depth at the panel lines. There will be 3 holes near the bottom flange to allow for 3 panel lines.
  • It also appears that transom with a tapered flange also exist while maintaining a uniform section depth
  • There is also the M2 and M3 Transoms identified in the US Bailey Bridge Field Manual

Acrow 300 and Mabey 100 transoms are?????

SUMMARY

What are the key factors that distinguish Bailey Bridges?

So far I can only tell Acrow 300 by its transom position.

What about:

UK Bailey
US Bailey
Mabey 100

Just found this really nice write up on the Bailey Bridge but it still does not completely answer my questions.

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    $\begingroup$ Why do you need to know? Is it for trivia? Are you buying them on ebay and don't want to get pieces that don't match your existing set? Are you trying to fill out the Wikipedia page? This comment may come off as flippant, but I'm confused as to the reason. $\endgroup$ – hazzey Jul 5 '16 at 21:48
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    $\begingroup$ I am trying to correctly identify one for an owner who has no documentation on the bridge (second time this has happened). They need a load rating eventually. Based on damage to a current structure I am currently looking at they may need parts. I want to know for future use when I look at these things how to correctly ID them. $\endgroup$ – Forward Ed Jul 5 '16 at 22:02
  • $\begingroup$ Why not hire a licensed inspector? He should be able to give you a good estimate of the load limit. $\endgroup$ – Carl Witthoft Jul 6 '16 at 11:54
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    $\begingroup$ I am a bridge inspector and have inspected 750-1000 bridges. Bailey Bridges are not the norm. I have the Bailey Uniflote Hand Book as well as the US Military Field Book for their versions of the bridge and I can easily say what the load capacity for their bridges are based on configuration. However since the UK Bailey and US Bailey used different alloys, and sections, and Acrow 300 has a different configuration, and apparently Mabey's design rectified some of the original Bailey's short comings it does not mean the manuals can be used interchangeably. Ergo proper identification is required $\endgroup$ – Forward Ed Jul 6 '16 at 16:06
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    $\begingroup$ yes that could be done, but without knowing which alloy belongs to which, it would be still guessing. If enough steel was pulled from the bridge coupon testing could be performed to determine strength. Then analysing the bridge using the material properties I could determine a load limit. However its not like I have an unlimited financial/time budget. One should still be able to visually assess (along with a measuring tape) which bridge type you are dealing with or which era. $\endgroup$ – Forward Ed Jul 6 '16 at 19:56
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This is well after your post but may answer some of your questions.
I was an engineer in Papua New Guinea durng the late 1970's early 1980s when Mabey began supplying Compact Bailey (now Compact 100), and we had a fair bit of older bridging to the "standard" design as well. At the time we used the data from the Bailey Uniflote book, but even then we had issues, as tables of available live load were not transparent on true capacity - they assumed a lowish dynamic load factor and were calcualted using working stresses. We tendered the supply (with Acrow and Mabey competing - well before the Chinese and Indians started supplying) based on the standard capacities. I don't recollect how much extra the Compact gave, if any, but they were only purchased in competitive tender against the standard Acrow product so we took no account of any extra capacity even if they had it.

Anyway, these days we still find ourselves occasionally load rating them and we still use the same approach - that is we use the data for the standard Bailey via the live load capacity tables, adjusted for dynamic factors and anything varying the dead loads. I believe, despite all the alloy and section changes, that the panels were designed to meet proof loading requirements, so in the end it still comes back to the table ratings.

We have only seen one compact among about a half dozen we have encountered - you can tell them easily by the absence of the transom clamp - the compact has a "permanent" bolted end. We treated it just the same.

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  • $\begingroup$ Thank you for that insight. If you ever get a chance to snag some photos showing the differences that would be greatly appreciated. Aside from the D.L.A. I think I wound up using the Bailey-uniflote handbook tables as is. There were some damaged components on one bailey so I wound up using the procedures listed for battle damage in US Military Bailey Bridge handbook. $\endgroup$ – Forward Ed Nov 30 '17 at 3:00

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