Construction processes as part of the design phase

Understanding and considering the construction processes during the design phase leads to more successful outcomes, said Steve McKechnie from Arup at GIRI’s members’ meeting. He illustrated this point with two examples of where design and construction went together with modern methods of construction to make light work of complex builds.

The first project was Terminal 5 at Heathrow. Steve took members through the design and construction of the roof and facades of the main terminal building, where the construction team used DfMA (design for manufacture and assembly) principles and focused on production delivery to complete the building on time and to budget.

He focused in particular on the 150m-long central rafter and explained how everything from the construction system to the temporary works were designed to optimise the build process to enable the rafter to be assembled in place.

“It worked brilliantly, because all the construction processes were built into the design. We worked as a team to think about how we would build it and how people would get access to do the work, and this approach was very effective.”

On the second project, a construction team had a rethink the build process on a church tower in Barcelona because the traditional methods and materials they were using were too heavy for the existing supports. The team approached Arup about using a steel diagrid as a structural system, which could then be clad in precast concrete panels and a layer of stone.

“However, the stone was itself a competent structural material. We suggested pre-stressing it with steel tendons to clamp the stones together and create a structurally integral panel. The construction department loved it because the masonry could be built off site and then lifted into place. And it turned out that the panel system was useful not just for cladding, but that it was also strong enough to carry the structural loads required by the tower.”

Steve shared three lessons learned from these successful projects. “Firstly, it’s so important to educate our designers, of which I am one. Designers must go to site and see the construction process so they understand how things will be built and the important factors to take into account in the design.”

And preparation is key. “By this I mean that we need to think through all the processes of construction required to finish a project. You will end up with a more successful product and you won’t throw lots of materials away.”

Finally, Steve echoed one of the key themes in the GIRI Design Guide – time spent on the design process is time invested not wasted. “This can be very powerful in proving the construction process. In both the projects I mentioned, we had very particular clients with very particular requirements. This meant we had to work in a different way to how we normally work in the construction industry, but it also gave us the opportunity to try something different and effective.”

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