Tees Vertical Lift Drawbridge
The Tees Vertical Lift Bridge, or Tees Newport Bridge spans the River Tees a short distance upstream from Tees Transporter Bridge, linking Middlesbrough with Stockton-on-Tees. Completed in 1934, it was the first large vertical-lift bridge to be erected in the UK. It no longer lifts, but still acts as a road bridge in its permanently down position.
The approach road on the north side of the river is carried on an embankment of blast-furnace slag for a length of over 3,000 ft. Midway along this embankment is a five-span all-welded steel bridge, crossing the former LNER Billingham Beck branch. Owing to the peaty nature of the subsoil and to avoid disturbance to the rail tracks, these spans are supported partly on 18-in. diameter octagonal reinforced-concrete piles, and partly on 4-ft. diameter cylinders, all of which were sunk to a depth of 70 ft. The total length of the bridge is 216 ft., and it carries a 38-ft. roadway, with a 9-ft. footpath on each side.
From the welded approach bridge and embankment, the lifting span is reached over three approach spans of plate-girder construction, while on the south side there are also two spans of similar construction, followed by a 154-ft. span of double Warren-type trusses. Continuing along the south approach, there is a reinforced-concrete box abutment, a skew span of 68 ft., and finally a 500-ft. length of embankment on a falling gradient, which is built between two concrete retaining walls.
The length of the lifting span between bearings is 265 ft. 4 in. Each of the towers is 156 ft. high above the carriageway, and when the bridge is in its “up” position there is a clearance for shipping of 120 ft. above high water. The clear width of waterway is 250 ft. The two main trusses of the lifting span are spaced at 43 ft. 6 in. centres. Each end of the span is suspended by 80 wire ropes, which pass over eight sheaves at the tower tops and are connected to four steel counterweight boxes. These counterweight boxes are partly filled with burr concrete, in which the ordinary stone aggregate has been replaced by steel punchings, the balance of the weight required being made up of cast-iron blocks. The sheaves are steel castings of 15 ft. pitch diameter. They are mounted on roller bearings, and are protected against the weather by hoods.
The electrical supply was taken through vertical bare conductors, attached to the river face of the south tower, and slipper collectors, to the machinery house at midspan on the top of the trusses. The AC supply was converted to DC by a Ward Leonard set, from which two 325-h.p. motors were supplied. These motors operated a series of geared shafts, connected to driving drums placed over the top chords of the trusses. Round these drums are wound the hauling ropes, which pass along the top chords, and then up and down the towers. The up-haul ropes are attached to the tops of the towers, and the down-haul ropes are attached at the foot of the towers. As the drums rotated, one set of hauling ropes was wound in, and the other set paid out, thus causing the bridge to rise or fall. Control was from an operator’s cabin slung under the machinery house in the centre of the lifting span.
The construction of the vertical-lift bridge and its approaches was begun in March, 1931. The engineers were Mott, Hay and Anderson, and the contractors Dorman, Long and Co.
The above information is condensed and partly transcribed from Engineering 1934/03/02
Dead load 2600 tons. Unbalanced load 12 tons.
As the counterweights descend, their effective weight increases due to the increase in length of cable descending with the blocks. To compensate, lengths of pitch chain are hung from the blocks, the other end being looped back to the bridge structure, so that the portion of weight of chain carried by the blocks progressively reduces.
See also Wikipedia entry for Tees Newport Bridge.