ANEWtransporter bridge, which has been under construction for the past three years over the River Tees, one of the great industrial waterways of North-Eastern England, was formally opened for traffic by H. R. H. Prince Arthur of Connaught on October 17th. Hitherto communication between the thriving town of Middlesbrough and the industrial area on the north side of the river has been maintained by means of a municipal ferryboat service, but, during recent years, this method of transport has proved both inadequate and inconvenient. Consideration has been given at various times to projects for a tunnel under 'the river, a suspension bridge, an ordinary swing bridge and also a rolling lift bridge. In the case of a busy river like the Tees, it is essential that any means adopted for accommodating the cross traffic should interfere as little as possible with the conduct of the up-and-down stream traffic, and if no other objections existed there would be no doubt but that a tunnel or high-level bridge would have afforded the best means for attaining this end. But both the tunnel and the high-level bridge, independently of high cost, would have involved the difficulties of approaches and in the case of a high-level bridge, this would, in a fiat district like that of Middlesbrough, form a practically insurmountable obstacle, so long as the bridge was utilized by the traffic passing over it in the ordinary way. Accordingly, in 1906, the Middlesbrough Corporation decided to replace the ferries by a transporter bridge. The Tees transporter bridge consists of two groups of piers erected on either bank of the river on masonry foundations and connected by a pair of lattice-type girders of 570 feet span with depths varying from 65 feet over the towers to 21 feet at the centers. The underside of these girders is 160 feet above high-water mark. The girders on the lower fiange each carry two lines of rails and are placed at a distance of 35 feet from center to center. On the four lines of rails there is supported a traveling platform from which a traveling car, 44 feet by 39 feet, is suspended. This car is provided with passenger cabins on each side, and its floor is level with the roadway on each side Passenger car approaching the Middlesbrough side. of the river. Accommodation will be found for about 600 passengers and six road vehicles. As the upper platform travels across the high-level girders the car is carried across the river between the landing places, the hauling to and fro of the traveling platform being effected by an endless ropeway. The ends of this rope are fixed on a winch placed on the south side of the river and driven by two 60 H. P. Westinghouse motors. The journey from shore to shore will be accomplished in less than two minutes. The working of the car will, generally be controlled from the pilot house placed on the top of the passenger cabin on the suspended platform, but in case of emergency it can also be worked from the winch house, distant about 150 feet from the main tower of the bridge on the Middlesbrough side of the river. One motor will, it is anticipated, be more than sufficient to propel the car, even in the most severe gale. The main girders are of the braced cantilever type and the extremities of the main span are anchored and secured to concrete anchorage blocks on each bank of the river by lii wire ropes embedded in concrete, each rope being capable of withstanding a breaking strain of 300 tons. Owing to the unfavorable strata the main towers on the Port Clarence side have been distanced 130 feet from the shore and approach is therefore made by a lattice girder bridge. On the Port Clarence side the foundations were carried down to 90 feet below high water of spring tide, and on the Middlesbrough side to a depth of 70 feet. The caisson foundations are filled up s o lid 1 y with concrete, and 10,000 cubic yards of concrete were used in these foundations and in the retaining walls supporting the same. After the caissons had been sunk and the steel towers sunk, the erection of the main girders proceeded simultaneously toward the land arm and over the river on the cantilever system. As the steel arms from each side of the river approached one another careful measurements as to levels and line had to be taken from time to time so as to insure an exact meeting in the center. As soon as they were within 100 feet of one another, exact dimensions were taken and after due allowance had been made for the proper measurements the closing lengths of the steel work that were required to fill in the gap were completed at the . contractors' works and forwarded to the site. Aided by favorable weather conditions, the 100 feet of closing lengths was erected in position in sixteen hours, the work coming together perfectly as to line and level. The temperature at the time of closing was 53 deg. Fahr. The height of the towers above high water is about 250 feet, so that the bulk of this work was carried out at a height of about 200 feet. Spiral stairways on one of the two towers of each abutment afford access to the main platform of the bridge and this passageway is specially illustrated in one of the photographs. The total length of the bridge and approach span is 850 feet, the length of each cantilever g i r de r overhanging on the landward side of the towers is 140 feet, and the extreme height of the bridge above -high water to the top of the center of the towers (i. e., to the top of the main posts of the cantilever girders) is 225 feet. The ba.se girders, on which the towers are built, have a length of 98 feet, a depth of 16 feet, and a weight of 163 tons. The total amount of steelwork in the bridge is 2,600 tons and there are 600 tons of steelwork in the caisson foundations. The total cost of the works and approaches, including buildings and all auxiliary work in connection with the structure, is estimated to be about $408,660. The Rabbit Problem in Australia RABBITS are well known to be the curse of Australia; notwithstanding the fact that, according to the view of the commonwealth meterorolo-gist, Mr. H. A. Hunt, the burrows of these animals, by keeping the ground broken up, make it more retentive of rainfall—a philosophical consideration that strongly suggests Mark Tapley. Latterly, the Australians have been trying with considerable success to turn their curse into a blessing by marketing their surplus rabbits (dressed) in European countries.
This article was originally published with the title "Novel Transportation Bridge in Great Britain" in Scientific American 105, 25, 556-557 (December 1911)