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 Institution Forums > Q&A > Analysis of portal frame View modes:  View mode Threaded Flat - newest to oldest Flat - oldest to newest
 Member piotr odron - 03/06/2013 23:23:24     Analysis of portal frame Hi everyone. Can anybody help me with pitched portal frame analysis and design to eurocode please. I have to analise a portal frame plasticaly without any software, only hand calculations ( it is for my dissertation ).I am not taliking about preliminary analysis where sections are determied. Is it true that graphical method is not allowed if designed to eurocode. Can I use virtual methode? Also is the position of purlins deterimned before the analysis or after?In analysis, is the vertical imposed load treated as uniformly distributed load or point load acting on the purlin. I have tried a couple of different analysis methods and they give a different distance of the plastic hinge in the rafter from the column,also different sorces recomend different ratio of moment in the rafter to moment in the column (0.75, 0.85)  .i suppose that elastic-plastic is the best but this would mean use a software( not an option) Can any one suggest most appropriate method for this task? Thank you
 Associate-Member (AMIStructE) Christopher Achilles - 04/06/2013 13:03:32     RE:Analysis of portal frame I was shown a simple way of doing an elastic analysis by hand before PC's kicked in properly in early 80's). You lay the frame flat including the legs (plan dims for rafters) then plot the free bending moment diagram for the rafters based on a unit load of 10kN/m. You then make a little table with height to eaves, height to end of haunch and apex height. You then have a punt at what the base shears will be and plot the base shear moment over the free bending moment. A bit of iteration is need but you can quickly reach a point where the moment at the haunch end matches the apex haunch (may take 4-5 stabs at the correct base shear). It is a simple method which gives you a unit bending moment diagram to work with. If your actual gravity load is 8.5kN/m then you take 85% of the results/shears etc. I was shown how to do it plasticly as well but my tiny brain started to hurt and I fell asleep!
 Associate-Member (AMIStructE) Christopher Achilles - 04/06/2013 13:22:12     RE:Analysis of portal frame I have just found my old training notes for Plastic Design (by hand) which may be of use. I can not work out how to attach them to this post but I could e-mail them to you (6 A4 sheets).
 Site User Peter Zsemebri - 04/06/2013 15:23:26     RE:Analysis of portal frame Hi, It is Piotr Odron who needed help with portal frame design. I have had to change my account as the old one does not work(it does not accept my e-mail for some reason). You have offered the notes for plasic frame analysis. I also have to analise a frame elesticaly so if you have any notes on plastic and elestic I would realy appraciate your help. Thank you for your help and look forward to hearing from you. My email is piotrodron@live.co.uk
 Site User Peter Zsemebri - 04/06/2013 15:24:41     RE:Analysis of portal frame thank you for help ,all
 Member (MIStructE) Micheal Toner - 03/02/2015 13:29:39     RE:Analysis of portal frame Christopher, could you email me your notes for plastic portal design by hand please?  To toner776@hotmail.com Many thanks in advance.
 Associate-Member (AMIStructE) Christopher Achilles - 03/02/2015 22:40:03     RE:Analysis of portal frame No Problem will dig them out and get them over to you tomorrow.
 Technician Member (TIStructE) Richard Lytham - 17/02/2015 11:20:13     RE:Analysis of portal frame Hi Chris, I was just looking through the forums and came across this discussion about portal frame analysis. Would you be able to email me a copy of your old design notes? richardlytham@leachsteel.com Thanks in advance. Regards Richard Lytham
 Graduate Thomas Roberts - 06/03/2015 12:11:50     RE:Analysis of portal frame If this is still a valid offer, i would be interested in these notes! Im particularly stumped in hand calculating the moment at the apex / ridge for the purpose of giving this information to the steel fabricator. Im a graduate engineer and have been relying on collegues to determine this using software (which isnt available to me at the moment). it would also be useful to understand the principles of what drives the moment here for future knowledge. tom_roberts.1992@hotmail.co.uk
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