Over-designing Steel Beams

What’s wrong with over-designing beams?

If you’ve ever used this website, you’ll probably notice that we design you the smallest beam size that will be considered acceptable by Building Control.

It’s possible that you’ve felt uncomfortable choosing the smallest beam; maybe you thought: Surely the bigger the beam the better and safer it is? That’s an understandable assumption but it’s simply not true. And here’s why…

A waste of resources and energy

Over-designing beams is not cost-effective and it’s a waste of resources and energy. Waste in the construction industry is a huge issue, as renowned academic and engineer Chris Wise explains in his video: ‘Enough is Enough’. Amongst other high-profile projects, Chris worked on the building of the 2012 London Olympic velodrome.

In that video, Chris highlights the lack of progress that’s been made in the area of efficient building design and construction:

“You’d hope that as we moved through time, we would get better at designing. But…if you just look at the amount of energy that was required to make the steelwork in the Sydney Olympic Stadium, it’s equivalent to the energy you need to drive about 80 million miles…

“If you move forward to the Bird’s Nest in Beijing 8 years later, that has got enough energy to drive 725 million miles, so nearly 10 times as much energy as there was in Sydney 8 years earlier, which to me is not a great sign of progress.”

Poorly designed steel beams

Over-designed steel beams make a significant contribution to this huge waste of energy.

Build Calcs founder Kevin Taylor used to work as a Senior Technician for a local authority and was responsible for checking calculations submitted for building regulations approval. In that role he saw projects with over-designed beams time and time again. It was the norm.

Kevin felt so frustrated that he decided to set up this website and other steel beam calculation websites, in a bid to provide more environmentally-conscious beam calculation reports, faster, and at a fraction of the cost.

Archaic load requirements

Chris Wise has also highlighted the role that over-designed steel beams play in energy wastage. In the ‘Enough is Enough’ video, he says:

“As an engineer, you have to resist every natural phenomenon acting on a building. And some of that is written down in the legislation, and it hasn’t changed much over the last 100 years.

“So this is the London Building Act from 1930, and in here it talks about the sort of loading you have to use…so it says, for an office or a counting house, you have to take a load of 100 pounds per square foot of floor area. Now that’s equivalent to something like 5 or 6 big blokes standing on every square metre of an entire floor of office, which is just ridiculous.

“Now we are still asked to design our buildings for that intensity of loading, which is simply nuts….By overdesigning and overspecifying every single office building, we are just throwing material off into the ether…we’re just wasting it.”

We’d have to agree. It does seem ridiculous that in over 100 years, our industry hasn’t updated and improved its knowledge of loads and how to accommodate them. Chris thinks the long-term answer to this problem could be more efficiently designed steel beams with tapered ends:

“[A steel beam has] been designed to be easy to make…the basic problem with having a beam which is the same all the way along is that the natural forces that act on it are not the same all the way along and so the perfect beam would be one which is shallow at the end and deep in the middle. And we’ve recently been talking to a very large international company who are keen to develop this technology…If that comes off and if it becomes in common use around the world we are going to save 120 billion car miles worth of energy every single year.”

To our knowledge his perfect steel beam hasn’t yet materialised. Probably because it involves persuading the steel industry to invest £25–£30 million to set up rolling mills that could produce these perfect beams*. On top of that it would mean a whole culture change within the construction industry, which won’t happen overnight.

We remain optimistic that Chris will see his ‘perfect steel beam’ concept realised, but in the meantime we’re trying to do our bit by not over-designing your steel beams.

*Source: Ingenia magazine, Issue 56, p.47