Tha Pai Bridge - allaboutpai.com
allaboutpai.com Tha Pai Bridge

The following piece was researched and written by Hak Hakanson, who long ago worked as a bridge inspector for the US State of Pennsylvania and clearly remains dedicated to the subject! This page is part of allaboutpai.com, which has lots of information about Pai, a town in the mountains of Northern Thailand.

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Tha Pai Bridge

The Mystery of Tha Pai Bridge

By Hak Hakanson

For the last several decades, Pai locals and tourists alike have visited the so-called "Japanese WWII Bridge," an old steel truss bridge that crosses the Pai River right alongside main highway 1095, about 4km south of Pai in the hot spring village of Tha Pai. However, as this document will reveal, the bridge is most definitely not of Japanese origin. In 2007, in order to elevate its status as a tourist attraction, the bridge was renovated and repainted, and a new and permanent public display was added at the southeast approach. The new display corrects the story somewhat, admitting that the steel truss bridge was erected not by the Imperial Japanese Army during WWII, but rather by a Thai government entity around 1976. However, the new display claims that the bridge spans come from the old Nawarat Bridge in Chiang Mai (which was removed around 1966 to make way for the current reinforced concrete structure). As this document will clearly show, this is also not the case!

So we have ourselves a mystery. Where did the spans of this bridge really come from? Were they added at the same time? Do verifiable photos exist of any bridge at this river crossing from WWII?

These are open questions for all the readers out there. In the sections below, we present the evidence available so far, and we invite any readers out there with further information, photos, or references to contact us at:

Contact
This page is an excerpt from a larger, detailed, evolving report about the Tha Pai bridge; email us at the address above if you're interested in seeing the full report.

Not the Nawarat

Any connection between the Tha Pai Bridge and the old Nawarat Bridge is easily disproven by a simple comparison of the two.

The appearance of the older bridge is well documented with photos hanging throughout Chiang Mai [photo by author of a print at Wat Gate Museum, originally taken by Boonserm Satrabhaya]:

Nawarat Bridge
Nawarat Bridge

Another more detailed photo of the old Nawarat Bridge [photo by author of a print at Wat Gate Museum; source is unknown]:

Nawarat Bridge
Nawarat Bridge

led to this schematic (not to scale) rendering of one span, which is a curved top chord Pratt through-truss [schematic drawing by author; all truss names in this article are per Bridge Basics at http://pghbridges.com/basics.htm]:

Nawarat Bridge Span Schematic
Nawarat Bridge Span Schematic

The other four spans of the old Nawarat Bridge were identical.

In contrast, the old Tha Pai Bridge is made up of four different types of trusses, some configured as 'through-trusses', others as 'pony-trusses', plus one very simple span, Span S3. Schematically, the old bridge looks something like this, as viewed from the north:

Tha Pai Bridge Span Schematic
Tha Pai Bridge Span Schematic

Counting from the east (the Chiang Mai end of the bridge, going in the same direction as highway stationing is increasing), the first two, identical spans (S1 & S2) of the old Tha Pai bridge are Warren trusses, modified with verticals, having straight and horizontal top chords [photo by author, 12 Jul 2008]:

Tha Pai Bridge Spans S1 and S2, with Span Schematic
Tha Pai Bridge Spans S1 and S2, with Span Schematic

Tha Pai's Warren trusses are quite different from the Pratt trusses of the Nawarat. Should the question arise, no, it wouldn't have made economic sense to have modified two spans from the Nawarat to take on this new appearance.

Thus, spans S1 and S2 of the Tha Pai River Bridge could not have come from the old Nawarat Bridge.

Following the first two through-truss spans is a very short span, S3, made of simple beams—no trusses [photo by author; 11 Feb 2008]:

Tha Pai Bridge Span S3
Tha Pai Bridge Span S3

It is an odd detail, but the point is that the steel for that span did not come from the Nawarat.

The next three spans, S4, S5, & S6, while not identical, are all pony trusses. The "outer" spans, S4 and S6, are similar in configuration, though different in length, and approximately symmetrical around an arched center span, S5. The truss configuration might best be classified as a Warren truss, modified with misplaced verticals. Top chords for S4 and S6 are straight and horizontal while that for S5 is curved [photo by author; 11 Feb 2008]:

Tha Pai Bridge Spans S4, S5, and S6
Tha Pai Bridge Spans S4, S5, and S6

Tha Pai Bridge Spans S4, S5, and S6
Tha Pai Bridge Spans S4, S5, and S6

The general symmetry of the three spans plus the same, unusual (indeed, peculiar) truss design suggests that they probably came from a single bridge of three spans. Further, in Span S4 is this "United States Steel Products Company 1930" manufacturer's tag—inconsistent with the Nawarat, which, according to a caption on a photo at Wat Gate Museum, was fabricated by "Cliffland Company, England" [photo by author; 09 Jan 2009]:

Tha Pai Bridge Manufacturer's Tag
Tha Pai Bridge Manufacturer's Tag

It is safe to say that none of the Spans S4, S5, and S6 came from the old Nawarat.

The last span, S7, is a pony truss, of a military expeditionary type—a Bailey Bridge [photo by author; 11 Feb 2008]:

Tha Pai Bridge Span S7
Tha Pai Bridge Span S7

The technology used in fabricating Span 7 is a generation later than that used in the old Nawarat Bridge. It could not have come from the Nawarat.

The simple conclusion to be drawn is that none of the spans on the old Tha Pai steel bridge came from the old steel truss Nawarat Bridge.

That said, the old Tha Pai Bridge, as it stands today, offers a unique selection of steel truss bridges in one spot that should be properly identified, described, and evaluated, for all to enjoy.

In that vein, many, many questions need to be answered, such as:

Again, we welcome any and all ideas, comments, or speculation at:

Contact

Copyright

Text and images from Hak's article are copyright 2009 Hak Hakanson.

Shameless Plugs

The following shameless plugs are from Chris Pirazzi, the creator of allaboutpai.com, not Hak Hakanson:

Support This SiteHas this site helped, informed, or amused you? Please support my work and ongoing site improvements in one of these ways:
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CopyrightAll text and images copyright 1999-2017 Chris Pirazzi unless otherwise indicated.
Support This Site

Has this site helped, informed, or amused you? Please support my work and ongoing site improvements in one of these ways:
donate now   Donate Now
Use your credit card or PayPal to donate in support of the site.
get anything from amazon.com
Use this link to Amazon—you pay the same, I get 4%.
get my thai dictionary app
Learn Thai with my Talking Thai-English-Thai Dictionary app: iOS, Android, Windows.
get my thai phrasebook app
Experience Thailand richly with my Talking Thai-English-Thai Phrasebook app.
get my chinese phrasebook app
Visit China easily with my Talking Chinese-English-Chinese Phrasebook app.
get thailand fever
I co-authored this bilingual cultural guide to Thai-Western romantic relationships.
See Also

You'll probably also like these sites...
slice-of-thai.com
Tasty morsels of information on Thai food, language, culture, and general silliness.
lurkertech: video tech and diversions
Buzzword bingo, bill the borg, MEZ, lurker's guide to video, and Thai, oh my!
mapfling.com: free custom maps with your own labels
Party? Meeting? Request a map, label it yourself, and easily fling it to your friends!
world's stupidest everything
See some of the worst the world has to offer, and add some of your own!
thailand your way
Travel with my friend Nang, who is a great nature, birding, and cultural guide.
jeed illustration
My English-fluent Thai friend Jeed is a freelance illustrator who is available for hire.
Copyright

All text and images copyright 1999-2017 Chris Pirazzi unless otherwise indicated.