What’s the big idea?

In 1930s New York, steelworkers balanced on beams even during the lunch hour.
At One Churchill Place in the 21st century, they used the far safer cherry-picker access platforms

If practice makes perfect, Canary Wharf Contractors must be getting close to perfecting the art and science of high-rise construction. Since the start

of the second phase of development at Canary Wharf in late 1996, it has erected six high-rise buildings, more than any other UK-based contractor.

This experience comes across in the attention lavished on seemingly inconsequential details such as the carbon and silicon contents of the structural steelwork. Charlie Paul, CWC’s structural construction manager, explains: “We check the carbon content so we don’t have to preheat the steel prior to site welding. We will also talk to Corus about the silicon content if we have to galvanise the steel.”

Paul had more than 30 years’ experience of steelwork contracting before joining CWC in 1999. Like most of its staff, he was hired for his specialist knowledge.

At Canary Wharf, says Paul, “you could make an early policy on how to construct the building from the conceptual design. If the architect and designers haven’t got it quite right as far as building it is concerned, you have an opportunity to change that.”

Senior construction manager Richard Lines adds: “On day one, the team gets together to start talking about what it’s all about and the details come out of that.”

From these discussions come ideas on which method of construction best suits the building, where to locate the cores and plant rooms, and where to site the tower cranes (see plan, right).

Don’t fence us in

On day one, the team gets together to talk about what it's all about. the details come out of that

Paul notes: “We may ask the designers to change some details so it gives us the option at tender stage to go for a slip-form or jump-form for the concrete cores.”

Lines says it is critical not to tie concrete contractors down to either method. “To get the economic benefits, you have to have a market where trade contractors will come forward and give their options.”

A huge amount of time is spent developing ideas: 19 crane layouts were contemplated for One Churchill Place, with detailed drawings indicating the operational capability of each crane and the designated positions for vehicles delivering materials. An internal review of the 19 schemes ended with seven options being made available to bidders.

Paul comments: “It meant contractor A could say my price is based on crane scheme X, while contractor B could say mine’s based on scheme Y. Nobody was disadvantaged and it was all about selecting the bidder based on programme, technique and money.”

He reckons solving the crane conundrum, which involved relocating cranes on top of the cores once slip-forming had finished, probably saved about £1m.

If the 210 m high cranes had been located elsewhere, the foundation works needed to support them would have been hugely expensive.

Paul adds: “To climb a crane externally from the lowest to highest levels would have cost £100,000. With five cranes that’s £500,000. So once you’ve added money spent putting the foundations in and taking them out, we must be talking about £1m.”

A couple of years earlier, while constructing 10 Upper Bank Street for law firm Clifford Chance, CWC came up with a novel tool to cut the time taken (sometimes up to four days) to raise tower cranes that were sited inside the building cores.

We’ve worked with the best trade contractors and pinched every idea they’ve got, added our own and developed it so we’ve overtaken the industry

The solution was the “Starship Enterprise” – so named because it consisted of two long steel beams at one end and counterweights at the other that looked similar to the spacecraft in Star Trek.

A crane would lift and position the Enterprise within its own mast. Next, beams were added to the two protruding legs to create a jacking platform off which the crane could be raised 30 m. This more than halved lifting time. Lines says: “We have only used the method once, but it is stored in our minds so we can use it again if it suits a particular building.”

Lightening the load

The attention to detail also goes into making sure the steelwork components in the structural design aren’t too heavy for the cranes. Paul says: “We have found instances where the cranes couldn’t do it. So we introduce a splice. For example, the column base plates on Barclays were 150 mm thick solid steel billet and 2 m square.

“Therefore, we put the base plate in, placed the column on top and welded the two together. That had already been decided before we went to the steel contractor. The average construction manager would not have gone into that level of detail and would have relied on the steelwork contractor to tell him that.” 

 For each works package, CWC’s specialists will examine every detail of the tender. Paul explains: “You can’t expect the surveyor preparing the tender to know about things such as the carbon content of steel.”

At the end of each project, all the parties involved are invited to comment on the lessons learned. A file nearly 25 mm thick was accumulated just for the steelwork package on One Churchill Place. Similar appraisals were undertaken for all the other trades.

Paul says: “We have worked with the best trade contractors and pinched every idea they’ve got, added our own and developed it to a stage where we’ve overtaken the industry.

“They still have unique products to offer us, but we hone them down to exactly what we want and what we need.”