KELBURN VIADUCT

Evening Post, Volume CV, Issue 118, 21 May 1928, Page 10

KELBURN VIADUCT

IS IT SAFE TO-DAY? SHAKEN BY TRAFFIC HEAVY LOAD RULE For some years past many residents of Kelbum and Northland who live near or pass over the Kelburn viaduct have frequently expressed doubt about the adequacy of that structure, designed in pre-motor days, for the carrying of such traffic loads as it has new to bear. . . ' ; Though the viaduct is getting older every day, the fact is that it is ' in better order now than a couple of years ago, for a complete overhaul was given the iron bolts and stays* which bind the piers and decking, and, at th,e Karori end, form the peculiar suspension,- or, rather, supporting, system. Each bolt and stay was looked to, cleaned up, and coated with a rust-prevent-ing paint. Eeplaccmcnts were made '■where necessary, and the bolts and stays were then so adjusted that each did its share of tho work. Generally the timber appears to be sound, but there is no question about the extreme vibration which takes place wheu heavy loads are travelling across the viaduct. A bicycle creates sufficient vibration at the Karori end to be felt, a light car definitely shakes tho whole structure, and when a loaded lorry or a bus crosses, the vibration■ is very pronounced. LOAD NOT TO EXCEED 10 TONS. At either end of the viaduct are notices, "Maximum loading 10 tons," which indicate the opinion of the officers of the City Council as to the tarrying capacity, allowing of course, for a safety margin. Whether oi not the placing of such notices would absolve the council from liability should a vehicle loaded to, sa,y 11 tons, try the pass and come to grief is a question open to much legal argument. If those notices can be" read to mean that the maximum loading on the viaduct at any .one time shall not exceed ten tons, that prohibition is broken several times every day; a bus, loaded with a good many more passengers than .the regulations allow, a lorry 'with the last brick packed in, and three cars may be on the.viaduct at the same time—just that combination did occur on Saturday, in fact. ' LONGITUDINAL DECKING. SUGGESTED. ■ When such loading occtlrs the vibration is'very marked, the whole thing ' shakes, largely because the "nice-king, running across the traffic line, has worn unevenly. . It has been suggested that much of the vibration —which is the chief danger, because in the long run ties and stays will be seriously weakened —would be removed if an additional hardwood decking -was laid d-qwn longitudinally. Decking running along, instead of across, tho traffic line was recently put on top of the old on the Pipe Bridge at Petone to ease the vibration strain on the water mains to the ■city. Longitudinal decking has also been laid over the stream crossing the Ilutt road at Kaiwarra to make the way smoother for the motorist. As a result of the paving of Upland road tho viaduct decking at the Kelburn end is several inches below tho pavement, and cars, buses, and lorries travelling from Kelburn drop and hit the planking ■with heavy, shaking blows. The additional decking, it is claimed, would bring the bridge surface level with the pavement, and do away with this pounding. The nest point is: Would the undcrstructure, particularly at the Karori end, carry the weight of an additional decking, plus traffic weight, and still give the safety margin that is essential? THE PICKET FENCING. It has beeil argued more than once that a very bad accident will sooner or later tako place when 'a car or a bus, for some reason or other, swerves or skids on the decking -and crashes through the picket fence on the southern side, and in support of that gloomy prophesy the spectacular escape ot a motorist who went through the fence at the Karori approach and tore down the impossible bank almost to the road below is mentioned. Actually the circumstances are quite different. That remarkably lucky driver hit the approach fence almost at right angles, but it would be almost impossible for a. vehicle to hit the main, fencing except at an angle. Heavy vehicles moving fast do peculiar things, and there is, of course, no guarantee that a lorry, a bus,-or even a car, would be stopped by the fencing, even though the palings are backed by fairly heavy timbers. The .case of tho driver who went down the bank brings out another point in regard to the picket fencing: that a driver crossing the viaduct, from Kelburn and another running up the main road to Karori are almost as completely hidden from each other as they Would be by a close-boarded or iron fencing, with a result that there is a constant danger of collision where tho viaduct meets the main road. If the'pickets were replaced by a heavy netting or by expanded steel this danger would be removed, and the fwicing at the same time might be considerably strengthened, at no very great cost.