Three Northumbrian Bridges
The first two bridges featured here are owned by the British National Trust and are checked from time to time by JK in his capacity as NT's bridge engineer. The first is the Allenbanks Suspension Bridge, spanning the River Allen to the west of Hayden Bridge in Northumberland. The bridge comprises a timber deck suspended on former colliery winding gear steel ropes with safety chains slung beneath. The bridge was rebuilt by JK's students in 1992, assisted by soldiers from nearby Albermarle Barracks supervised by John Knapton and Lieutenant Stuart Taylor from Albermarle. Since then, John Knapton has carried out periodic structural assessments.
Allenbanks Suspension Bridge
In 1992, the bridge was in a dilapidated condition and in particular, the suspension ropes had stretched so far that the bridge became submerged during flood conditions and National Trust had closed the bridge in 1991. The reconstruction began with the removal of the deck so as to allow access to the cables beneath. Each cable was cut and shortened and the two ends were rejoined after a turnbuckle had been inserted. The turnbuckle allows the cables to be tightened further should further stretching of the cables occur. The 1997 inspection revealed no stretching and the only maintenance required was the tightening of one nut connecting the safety rail to the deck. The turnbuckles are shown below. Note how the turnbuckle has been secured by steel clamps to prevent the general public from raising or lowering the bridge.
The new timber deck was constructed by sawing planks from trees felled in the local Allenbanks woodland as part of the National Trust Forestry management program. The cutting and rejoining of the ropes was undertaken by Tyneside engineering company, Clarke-Chapman, part of the Rolls Royce Group. The deck is shown in its 1997 condition below.
In 1992, JK undertook his initial survey of the National Trust's Cragside Bridge in Northumberland. The bridge links Cragside Hall to the estate's walled garden and has been closed to the public for a number of years because of corrosion to its iron structural members. The third diagram shows how the bridge deflects in windy conditions. Throughout the 1990's, JK undertook regular inspections of the bridge and in 2002 was appointed by National Trust to be project manager for a £250,000 refurbishment of the structure.
The next four pictures illustrate a Bailey Bridge, near to the Allenbanks suspension bridge over the River Allen in Northumberland. Bailey developed the steel bridge so it could be assembled quickly by soldiers. It comprises lightweight steel units which clip together. The bridge has a timber deck. Note the clips. Bailey and John Knapton were both pupils at Rotherham Grammar School.
The above picture shows the top of the handrail where two structural panels are pinned together. A casting is welded to the right hand panel and is pinned to the left hand panel.