Reaching new heights in the 21st Century

Cityscapes, today, defy belief. Think, for example, of Shanghai, Dubai, Kuala Lumpur and, closer to home, London. A forest of tower cranes assembling buildings ever more fanciful, striking and vertiginous in shape, style and height. A theory, popular around this parish, is that world leading architects convene annually and, after consuming some mind altering substances, submit their latest blueprints to their peers for appraisal. The most bizarre designs being deemed the winners and promptly rushed through the planning process. There is no holding back and the only limiting factor to the scale of these creations would appear to be the flight paths of aircraft in the locality. So far, all well and good. However, this is where reality kicks in! Someone has got to make this happen, to translate a pretty picture into a viable, achievable entity. And this happy task falls to the Structural Engineer. In rugby, it would be called a Hospital Pass but in engineering terms, it is an opportunity, a challenge and a way of life.

In times gone by, and with unlimited greenfield sites, if great height was required you would increase the footprint of the structure (see Pieter Breughel the Elder's " Tower of Babel" for an example).

tower of babel2

Sadly, this is not feasible today in a modernising city where the ground space available for a new build equates to that of its recently demolished predecessor. Faced with this conundrum and the need to maximise elevation our engineer has limited available options. For the purposes of this article, the use of High Strength Steel will be the focus.

It doesn’t seem too long ago that EN10025 S275JR steel was all pervasive in structural engineering circles but almost overnight S355JR supplanted it and that remains the case for low rise buildings such as portal frames, hospitals and schools. But as the complexity of projects increases, the need for higher strength steels also increases and although steel grades as high as S1100 and beyond are available, current best practice is based on S460 fine grained low temperature steels, or EN10025:3 S460NL to give its full title. Its superior characteristics allowing for both weight-saving and/or greater strength depending on the application. Of course, designing around higher grades is one thing, obtaining them is another, and it will come as no surprise to you, dear reader, that this is where Brown McFarlane enters the equation.

Having held stocks of the grade for over 15 years Brown McFarlane was ideally positioned to answer the call when fabrication work commenced on 22 Bishopgate in the City of London towards the end of 2016. This 278 metre high mega-structure was being built on piling constructed for an earlier aborted project and to utilise this original piling, massive Transfer Beams and Nodes, incorporating machined plates up to 250 mm, were required. The months of November and December were to prove frantic and demanding as Brown McFarlane set about profiling, drilling and machining these critical components for delivery to its client in the build up to Christmas. All the deadlines were met and work was able to commence, on schedule, on site in January 2017. As the contract progressed it was recognised that some refinement of its stock range was required and soon all S460NL plate was being purchased with Z35 Through Thickness Testing as standard. The decision to increase available thicknesses was also reached and before long 200mm S460NL was to become readily available.

Steelwork on 22 Bishopgate continued for another 2 years and several hundred tonnes of machined profiles in S460NL were supplied by Brown McFarlane. During this period, it became evident that demand for the product was becoming more and more widespread. And not just for skyscrapers; there are some amazing things happening at 21 Moorfields too! In effect a bridge, over a railway, like no other but also the UK headquarters for Deutsche Bank. The use of S460NL plate, from EN14001 approved steel mills, has been essential in realising this mind-blowing concept.

Looking to the future there are already several further titanic structures looming large, the most impressive, by height, being the inappropriately named (for the present anyway) 1 Undershaft at 290 metres. It is followed by 100 Leadenhall Street at 249 metres and 6-8 Bishopgate clocking in at 203 metres although somewhat dwarfed by its near neighbour at No 22. Meanwhile, Brown McFarlane is looking forward to the day when the first of the layout drawings land on the structural engineers’ desks. With its unrivalled battery of profiling, drilling and machining equipment and its comprehensive stock range, Brown McFarlane and BMPE (Brown McFarlane Precision Engineering) are in the ideal position to provide the beleaguered structural engineer with an instant solution to and a perfect fix for his immediate and colossal challenge!”