Popular Content

Showing most liked content since 01/23/17 in all areas

  1. 1 like
    Hello, I have posted some spreadsheets for the design of bolted beam to column connections according to EN1993-1-8. I would be glad if you will use them and inform me of any errors. And also if you have some suggestions please tell me. The spreadsheets are now in moderation queue, but I hope they will be available soon.
  2. 1 like
    These equations must be satisfied if you don't want to make an explicit check of the rotational capacity of a particular section (or rather a region of a structure). In general there indeed is no direct restrictions on x/d if one doesn't assume any redistribution of elastic moments in the structure. In any case it would be good practice to design section with ductile behavior, which in general can be accomplished by limit x/d to that given of the equations 5.10 (thus implicitly taking care of rotational capacity of section), because the limit in equations 5.10 will still depend on the amount of moments redistributed. ISE manual also suggests limiting x/d to 0.45 to achieve ductile behavior. Here are my two cents... The thing is that you could design section to be balanced x/d=0,617, though I always remind myself that I'm just a human and human errors do happen in design offices - seen them, made them. So in any case if you design ductile sections there is added safety to the structure, for examples, because if you underestimated settlements of some foundations there may be a situation where hogging bending moments in the support region in a slab are higher in real life than those you've assumed during design, and if that region won't be ductile enough it could lead to failure of the structure. By that I want to say that I always design liming x/d<=0,45 or smaller, if appropriate. Cheers
  3. 1 like
    Apologies if someone has already mentioned it, but I could not see any reference to the RCC spread sheets available from the Concrete Centre (UK). These are moderately priced, I think, and very useful.
  4. 1 like
    48m cantilevered buildings are a little out of the ordinary and I don't think it's a question that you can realistically ask in a forum like this and hope to get a comprehensive answer. The only thing that springs to mind for me is something like a cable stayed solution (which takes away the cantilever, or part of it, of course) or some kind of arched or inclined support under the cantilever part. It sounds like a job for a specialist company, especially if it has any chance of being dynamically loaded.
  5. 1 like
    Think of the picture. Column - slab system. Where could the plastic joint be created? Only is columns. That's why for such cases capacity design is officially dead . That's what I thought too.
  6. 1 like
    I have been involved in a lot of flat slab construction. It is economic and practical for many reasons. Ion has already mentioned some but there are more: fit-out of partitions etc. is easy as it does not need to cut around beams etc, services can go anywhere and do not have to align with or penetrate beams, it is fast and form-work is saved (labour and material) especially if you use filligree systems. Room layout is easily changed as there are no beams to follow. Dubai is actually in a moderate seismic zone and they are conscious of it. When I did some work there, they required significant beam strips in flat slab construction. Flat slab construction in its pure form, is not allowed in some places (I think California is another example) but you can put in beam strips or incorporate things like 'Deltabeams'. Disadvantages of flat slab are its sensitivity to progressive collapse and you have to be careful with the design, especially punching shear. A punching failure would cause the load at the column to shed to surrounding columns and, because the load application could be sudden, a dynamic magnification may be applied and this could be up to around 2 (but is likely to be less). In seismic areas, there is also a danger of degradation of the slab/column junction due to repeated reversals of large sway deflections in an earthquake - this rotates the column back and forth where it goes through the slab and soon breaks down the concrete, which then becomes weakened in shear. A good deal of flat slab construction is made even more efficient by using post tensioning. Bubbledeck is also a good system that achieves some advantages of PT without the PT.
  7. 1 like
    That's right. That's right. That's also right but this influence doesn't appear in calculations. Two are the basic differences between B500a and B500c: 1st is that B500a has not a discernible yield limit point in the stress-strain diagram like B500c has. 2nd is that B500a has not a clear fracture limit like B500c does. This is a major issue in capacity design and this is the answer why in seismic regions B500c is used (not only for its ductility but also for its upper fracture limit). Because of ductility, the total elongation in maximum load for B500c is 7,5% and for B500a is 2,5%. These ductility differences have also some other impacts e.g. in choosing mandrel diameter.