WHEN BRIDGES BREAK.

New Zealand Herald, Volume LXVI, Issue 20229, 13 April 1929, Page 2 (Supplement)

WHEN BRIDGES BREAK.

REMARKABLE CRASHES. STORY OF TWO MOTOR-CARS. EFFECT OF CARELESS DRIVING. Broken bridges are such a rare occurrence in England, says a writer in a London newspaper, that it is difficult to realise tliat, throughout the world there are dozens of failures every year. A wellmade steel bridge looks as though nothing less than an earthquake could shift it. But actually it is quite a delicate structure, and only one of the vital steel girders need bo damaged for tho whole bridge to crash. In November, 1922, a carelessly driven car smashed one of the end girders of a bridge at Tyrone, Pennsylvania. The result was that one side of the bridge was ripped off its bearings at one end, badly twisted, and damaged beyond repair. But, strangely enough, the floor held good. Tho bridge was closed for rebuilding, but, a few nights later a second ear crashed through tho barricade, swept the red light out of its path, got out of control on tho tilted roadway, and plunged through tho handrailing into tho river on tho other side. But it hardly damaged tho bridge at all. The first car hit a vital spot; tho second did not. Smashed by a Steamer. In December of the same yoar a swingbridge in England that carried the Sou tilEastern and Chatham Railway over the River Swalo met its fate. Tho river is on'jy wide where tho bridge spans it, and tho 7000 ton steamer Gyp was endeavouring to make tho passage. Tho boat was 48ft. wide, and tho owners were warned not to take tho risk, as there was so little clearance for it to get past (ho bridge. But they decided to try. In the middle of tho narrow stream tho steamer swerved, hit one of tho bridge piers, and took it on with it up the river. Many a bridge has suffered from river traffic in this way. Four years ago tho lumber schooner Martha missed its courso on a river in Oregon. There was a big steel bridge carrying the Southern Pacific Railroad over the stream, with a 180 ft. opening span in tho middle. The steamer missed tlie channel and hit one of the fixed spans of the bridge at the side of tho opening. Tho span weighed 300 tons, but tiio Martha knocked it off its piers, and it sank in 28ft. of water. Bridges aro very rarely blown down nowadays, since engineers profited by the lessons of the Tay Bridgo disaster, but plenty of them are swept away by floods. One case occurred where a wTiole railway bridge was washed out, and only tho rails remained, spanning tho flood, with the sleepers clinging on here and there. An Unlucky Bridge. In January, 1923, fiftepn people were drowned when one of the five-strand cables of a suspension bridge snapped at Ivelso, in Washington. Tho disaster would not have been so serious, but the floor of the bridge sagged and was caught by the swift six-mile-an-hour current of tho Cowlitz River. Tho remaining cables parted like pistol shots; the timber towers at the ends of the bridge were overturned, and in less than a minute the wreckage was complete. This bridge was particularly unlucky, as it was only built in 1905. was washed out next year, replaced in 1907, and then crashed again sixteen years later. As it cost some £IO,OOO to build, and on top of this tho county was found liable for the accident, tho people of Washington must have thought themselves very badly used. Among the old timber bridges of Canada and tho United States hundreds have been burned down by sparks from locomotives crossing them. But probably the most curious case of destruction by fire was that of a suspension bridgo at Franklin, in Pennsylvania. The fire broke out in a building at one end of the bridge. Slowly, as tho heat became greater and greater, the lead securing the cables into their anchorage sockets melted. At last the cables pulled out, and the whole bridgo tipped into the river. An Unaccountable Crash. Many failures aro not so easily accounted for as these. Only a few years ago a concrete arch was being built over tho River Bigge, in Germany. It was noticed that the concrete did not seem to liavo set very well at the centre of tho span, but the bridge was finished and the temporary timber staging was removed from under it. At first nothing happened, then suddenly at noon the arch collapsed. Only by a great piece of link were there no casualties, as tho crasli came just after the workmen had knocked off for lunch. Probably the most unaccountable of all crashes was that of a timber bridge at Los Angeles in 1924. The day beforo the smash an eight-ton roller and a fiveton asphalt truck had been at work on (he bridge, with many other vehicles crossing at the same time. The bridge, which was inspected annually, stood the loads perfectly. Next day. when the roller and truck bad left, it broke under the weight of one pedestrian and a motorcar and foil 40ft. to the river-bed.