Tenryu Bridge, Tokaido Main Line, c. 1930.



1930sBridges & SpansOutside TokyoTechnologyTransportation
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“A serious problem which is presented to the Japanese engineer is the heavy periodic rainfall and its effect on the variation in runoff of rivers and the construction of bridges.

“On this account, coupled with the absence of water storage either by natural or artificial reservoirs, the river valleys which at certain times are roaring floods are for a great part of the year wide flats of gravel and water washed pebbles. Such flats form convenient quarries for obtaining railway ballast which has only to be shoveled up, sifted and graded, but the wide valleys required bridging and the results is a number of long low multiple span bridges.

“The most striking of these is that across the Tenryu River, 164 miles from Tokyo. This is a 19-span through truss bridge, 3900 feet in length. Long bridges of similar construction are encountered repeatedly along the lines of the railway.”

“Railways of the Japanese Empire”, by S.T. Dodd, General Electric Review, April 1924

Tenryu River Bridge, Tokaido Main Line, c. 1930. Between Hamamatsu and Kakegawa, in Shizukoka prefecture.

The almost 4000-foot-long Tenryu River Bridge, Tokaido Main Line, c. 1930, between Hamamatsu and Kakegawa, in Shizukoka prefecture. Completed c. 1890, it was designed by British bridge architect C.A.W. Pownall. The wide variation of river runoff required long bridges over river bottoms that are usually dry but which become roaring torrents during monsoon seasons.

“British bridges also remained popular with Railway Agency, which employed British bridge experts until almost 1900. The most famous one was C.A.W. Pownall, who designed and ordered British bridges for government lines like the Tokaido and did not retire until 1896.

“From the start, the British favored bridges with the Warren truss (diagonal web members, like triangles, between the top and bottom chords). For the Tokaido, Pownall increased the length of each span from 100- to 200-feet. These he linked into daringly long iron bridges across the broad Nagara, Ibi, and Kiso Rivers.

“In 1888 he designed his longest bridge of all across the Tenryu River near Hamamatsu: nineteen spans of British wrought iron and steel, each with 200-foot-long intersecting Warren trusses (forming double triangles, like rows of ‘X’s).”

Meiji Revisted: The Sites of Victorian Japan, by Dallas Finn, 1995

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