Site Visit

Last week I had an opportunity to go on a site visit in East London. It was an interesting project; a school in a busy area of Aldgate that had no outdoor space and so were constructing a gymnasium on the roof of the building. The existing building is of concrete construction and the extension is a steel frame.

The visit was a brilliant insight into the obstacles and challenges faced on a construction site and how they are overcome. On this project there were a number of restrictions on space and time, for example, simply getting the steel onto the roof of the existing building without a road closure (which only would’ve been possible at the end of August, which would’ve far too late).

The gym was to be made up of two basketball courts and so of course there couldn’t be any internal columns, however the long steel beams that supported the roof were too long for the equipment used to get them on site. So they had to be cut up and reconnected on site. When I was there they were in the process of removing the temporary supports.

Another issue faced by the contractor was noise. Walking through Aldgate you can see a huge amount of construction going on so this is normally not a problem, however when working on a school project, especially when demolishing the existing roof structure (during exam season!). It required a huge amount of planning to ensure that no-one’s studies were interrupted by the works. The layout of the steel structure was generally dictated by the layout of the existing columns below and the contractor informed me that drilling in the column baseplates had caused noise and reverberations all the way down to the ground floor.

All in all it was a great chance to see how a construction site works and learn about the kind of things you can’t learn at university. From the health and safety aspects to the finer details of construction, it was an invaluable experience.

Composite Construction

Cycling through the city this week I came across a construction project near London Bridge:

The project utilises composite decking, probably one of the two most popular methods of construction for medium rise buildings (along with flat span reinforced concrete). In composite construction, steel beams and reinforced concrete floor slabs are connected, (using profiled decking and welded studs) which transfer the shear between them and allow them to act as one composite unit. Thus a higher proportion of the concrete floor slab at the top of the beam can be under compression and a shallower section can be used.

Another feature of the building which can commonly be seen is cellular beams, i.e. steel beams with openings in the web. This is mainly so services can easily be channeled around the building where required. The various advantages of this design are evident; the decking, as well as providing permanent formwork for the concrete flooring can be used as a safe platform during construction, and technical guidance is produced by the decking manufacturers, which can be a great aid at the design stage.

So as this is a pretty vital bit of structural design for an engineer to get their head around, I thought I would have a go at broadly designing one of the sections to ULS, albeit with a few caveats and assumptions:

So there’s the initial sizing of the beam. There’s still far more to be done of course, as the web openings will complicate matters. Vierendeel bending (that is, a complex hybrid of shear, axial and bending interaction at the corners of the openings) must be accounted for, as well as the usual checks of deflection and vibration to SLS.

Balcony Design

Cycling home earlier this week through Bermondsey in the sun, I found myself looking at the balconies on some of the flat blocks near the Old Kent Road. They’re interesting from a structural point of view because the structural elements are often exposed and you can get a sense of how they were designed. So, I thought I’d have a go at designing a couple of structural elements, as inspired by this balcony:

I’ve had to make a few assumptions and estimations about the dimensions of the balcony, but it’s a good exercise in structural design. Structural elements such as timber beams and cantilever steel beams are more likely to pop up on balcony than elsewhere on building projects, so they provide something of a individual challenge for the designer.

Structural Analysis Notes

I’ve recently been making little infographics for some basic structural analysis topics, partly as a bit of revision for me as these things can sometimes fall by the wayside when you focus on the more complicated topics, but also because I find it immensely satisfying to create these little aesthetically pleasing notes. They’re pretty time-consuming so I’m not sure I’m going to be able to produce them all the time but the first two are below: