During these first few weeks of my placement I have been carrying out some fairly entry-level calculations on a forty-five storey tower. These follow on nicely from courses in concrete and steel design that I took during my first term at ENPC. However, while these courses were based on the new Eurocode regulations (currently being adopted in the U.K. and in France), the company I am working for is in a transition period during which it is using the new code for some projects and the old French code for others.
During the first few days I therefore had to get my head round these older regulations that I had never seen before. In particular I was getting hung up on the issue of how much a beam should bend in service. While a bending beam may not necessarily break, it may cause temporary walls to crack and finishes to become damaged: hence the limits on how far a beam can deflect in everyday use. Both codes have similar limits for this deflection; the only difference is in how you calculate the deflection. The Eurocode is a lot more flexible (read vague) on how to perform this sort calculation than the French code. I spent a long time going into the detail of how to apply the French code and got quite confused. Everyone that I asked had their own way of doing it but no one seemed to have a definitive answer (this was not helped by the fact that those who do know are rushed off their feet). In the end, I found that these technicalities accounted for minor differences and I was able to move on. I remain unsatisfied however with my methodology.
Once a methodology is established, calculations can be automated with Excel. Everyone has their own Excel sheets to speed things up. Or at least that is the idea. When the sheet is up and running, it is very easy to rattle off calculations, but getting it to work is the difficult part and I sometimes wonder whether the time taken verifying the code doesn’t add up to more than it would have taken to do the calculations by hand. It is also very difficult to follow your working in Excel, and even harder to follow someone else’s. The biggest challenge is making these automated calculations readable to others.
As well as the program for dimensioning beams, I am now on the second version of a program that will work out an approximate cost for this tower. Something that started relatively simply has spiralled out of control, hence the second version. I hope to be able to report progress tomorrow!
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