Climbing high

Its four great chimneys still stand and, while the site has been through the hands of various speculators and yielded vast profits as it has changed ownership, nobody has yet managed to gain permission to demolish it. So far, successive governments and local authorities have insisted that the shell of the building and chimneys must remain in whatever development scheme is finally adopted. Provided, of course, the remains of the building do not collapse in on themselves in the meantime. And that's where the problems lie. For the chimneys are not the mighty brick structures many might think, but are made of concrete that is a mere 150mm thick, reinforced with steel that is becoming ever more corroded. Since they cannot be demolished with explosives, because of the proximity of other constructions, someone is going to have to go up those chimneys, either to repair or take them down, piece by piece, before rebuilding can begin. They were originally constructed with the assistance of massive amounts of scaffolding, in an era where health and safety was less of an issue than it is today. The cost of repeating such an exercise is likely to be prohibitive. The Challenge Our challenge this month is to come up with a way of getting workers and machinery up the chimneys -- so that the necessary work can be done -- then safely down again. We are advised that attaching anything heavy to the outside with anchor bolts is out of the question, and would almost certainly bring the structure down. One company that specialises in tall structure inspection has developed a modern technology-based piece of equipment that could do the job. While it has not been taken up at Battersea after the last change of ownership, it is being applied to the repair of another large chimney not a million miles away. The basis of the equipment is described below. Once you read it, you will probably agree that it is the only sensible way to approach the problem. For those without access to the web, the solution will be described fully in our January 2008 edition. See if you can come up with a better way to rescue what has become something of a national, if rather cheerless, treasure. Solution A working platform designed to enable the demolition or repair of Battersea Power Station's chimneys was one of several solutions devised by Nigel Matthews of Delta International, which is based in Oldham. "The material condition is so poor that it cannot take the weight of anchors, so we needed a platform that would keep the chimney in compression and ensure a uniform axial loading," he said. Adhesion is provided by two circumferential bands, secured by bolts and tightened by electric torque wrenches. After clamping one ring, the work platform is pulled up by 12 electric actuators. After this, the work platform ring is clamped and the upper ring pushed up again. Each push-and-pull cycle raises the platform by 1m. The actuators would use controllers made by Control Techniques. "We had to incorporate so many interlocks and fail safes into the design, and an audible alarm when the platform was about to move, so Control Techniques was the company to go to," adds Matthews. While this particular platform has not been constructed, a very similar one is being used to reinforce a 140m high refinery chimney in Southend. The reinforcement consists of adding an additional 150mm of reinforced concrete to the outside.TS