WHEN BRIDGES BREAK

Hokitika Guardian, 19 April 1929, Page 7

WHEN BRIDGES BREAK

HEM A RKARL E CRAS 11ES

.Broken bridges are such a rare occurrence in England (says a writer in a London newspaper) that it is difficult to realise that throughout the world there are dozens of failures every year. A well-made 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 be damaged for the whole bridge to crash.

In November, 1022, 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 ropped off its bearings at one end, badly twisted, and damaged 'beyond repair. But, strangely enough, the floor held good. The bridge was closed for rebuilding, but a few nights later a second car crashed through the barricade, swept the red light out of its path, got out of control on the tilted roadway, and plunged through the handrailing into the river on the other side. But it hardly damaged the bridge at all. The first ear hit a vital spot; the second did not.

SMASHED BY A STEAMER.

In December of tbo same year a swing-bridge in England that carried the South-Eastern and Chatham Bailwav over the river Swale met its late. The river is only 581 feet wide where the bridge spans it, and the 7(XX)-ton steamer Gyp was endeavouring tO' make the passage. The boat was 48 feet wide, and the owners were warned not to take the risk, as there was so little clearance for it to get past the bridge. But they decided to try. In the middle of the narrow stream the steamer swerved, bit one of the bridge piers, and took it on with it up the river. Many a bridge lias suffered from river traffic in this way. Four years ago the lumber schooner Maltha missed its course on a river in Oregon. There was a big steel bridge carrying the Southern Pacific railroad over the stream, with a 180-foot opening span in the middle. The steamer missed the channel and hit one of the .fixed spans of" the bridge at the side of the opening. The span weighed 300 tons but tiie Martha knocked it offi its pier and it sank in 28 lent of water.

Bridges are very rarely blown down nowadays, since engineers profited by the lessons of the Ta.v Bridge disaster but plenty of them are swept away by Hoods. One. ease occurred ’.Chore yi, whole railway bridge was washed out and only the rails remained, spanning the flood, with the sleepers clinging on here and there.

AN UNLUCKY BRIIX3B.

In January, 1923, 15 poopl(> were drowned when one of the five-strand cables of a suspension bridge snapped at Kelso, in Washington. The disaste would not have been so serious, but the. floor of the bridge sagged and was caught by tin* swift six-mile-an-hour current of the Cowlitz River. The 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. The bridge was particularly unlucky. as it was built only in 1905. was washed out next year, replaced in 1907, and then crashed again 10 years later. As it cost sonic £IO,OOO to build, and on top of tins the countv was found liable for the accident the people of Washington must have thought themselves very badly used. Among the old timber bridges of Canada and the United States hundreds have been burned own by sparks from locomotives crossing them. Tlul probably the most curious case of destruction by fire was that ol a suspension bridge at Vranlin Pennsylvania. The fire broke out in a building at one end of the. bridge. Slowly, as the heat became greater and greater, the lead securing the cables into tlmir anchorage sockets melted. At last the cables pulled out, at.d the whole bridge, tipped into the river.

AN UNACCOUNTABLE CRASH

Alan.v failures are not so easily accounted for as these. Only a few years ago a concrcto arch was being built

over the River Bigge, in Germany. It was noticed that the concrete did not seem to set very well at the centre of tlic span, but the bridge was finished and tiie temporary timber staging was removed from under it. At first Ho-

ming happened. then suddenly at noon the arch collapsed. Only by a great piece of luck were there no eas.aitics, as the crash came just after .lie workmen had knocked off for lunch Probably the most unaccountable of a,ll crashes was that of a timber bridge at Los Angeles in 1921. The day before the smash an eight-ton roller and a five-ton asphalt truck had been at vork on tin 1 bridge, with many other vehicles crossing at the same time. Tiie bridge, winch 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 motor ear and fell 40 feet to the river bed.