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The Johnson Street Bridge is a bascule bridge that spans the harbour of Victoria, British Columbia. It is commonly referred to as the "Blue Bridge" because of its distinctive blue colour. The bascule spans were designed by the Strauss Bascule Company Limited and were fabricated in Ontario. The sub-structure was built by the City of Victoria Engineering Department and required of concrete. The bridge was completed in January 1924 at a cost of C$918,000. The bridge originally had street car rails running down the center of the road span, but they were never used, and were removed a few years later. The original wood deck was replaced by a steel grid in 1966 and the steel structure was repainted in 1979 as part of an extensive renovation. The bridge had two opening spans of that operate independently, a three-lane highway span of 350 tonnes and a railway span of 150 tons. The approaches are fixed girders, the east is and the west is . The counterweights are made of hollow concrete and total 780 tonnes. Daily traffic in 2010 is 30,000 trips a day at peak usage, of which 4000 are pedestrians, 3000 cyclists, and 23,000 vehicles. Until 2011, the rail span for the E&N was used twice a day by the Via Rail Dayliner, for trips up the island towards Duncan, Nanaimo and Courtenay. The rail span and counterweight have now been removed. ==History== The Johnson Street Bridge was designed under the direction of Mr. F. M. Preston, City Engineer in 1920. This is a Bascule-type bridge in which one end rises while a counter weight lowers on the opposite end. When it was built, the Johnson Street Bridge had two separate Bascules, the Railway section and the Highway section. The Railway span was removed in 2012 after it was deemed to be in such a poor state of repair that it posed a danger to the pedestrians and cyclists who were using it and any marine traffic passing below it. The railway had not been used by a train since the E & N passenger service was suspended in 2010. The Strauss Bascule Company Limited, which held the patents on the design, prepared the design for the bascule spans and the operating machinery. Joseph Strauss later went on to design the Golden Gate Bridge in San Francisco. The superstructure of the bridge was fabricated in Walkerville, Ontario and contains 100 tons of steel. The City of Victoria Engineering Department built the sub-structure of the bridge. It required of concrete. The main opening span is in length and when in the open position is balanced over a fixed span. The eastern approach is spanned by a fixed girder while the western approach has a fixed girder. The counterweight block on the highway span is a hollow concrete structure and contains a number of smaller concrete weights and tips the scale at over 780-tons. It balances the 350-ton opening span. The linkage is moved by two large racks which are driven by two electric motors. The Johnson Street Bridge was completed at a cost of $918,000 and opened in January 1924. The original deck of the bridge was constructed of wood timbers. Besides being slippery in wet weather, the timber absorbed water and became heavier which affected the balance and placed excessive loads on the opening machinery. The timbers were replaced by an open steel grid decking of constant weight in 1966. In 1979, extensive repairs were made to the superstructure, which had become severely corroded. The blue paint now on the bridge was selected because the oxides of its pigment are the same colour as the paint so that little fading of the colour occurs. In 1995, abnormally high temperatures caused the steel decking to expand to the point the bridge would not open or close properly. This necessitated the removal of about of the decking. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Johnson Street Bridge」の詳細全文を読む スポンサード リンク
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