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  1. Yesterday
  2. Agree about the tensile stresses... some of my first work as an engineer was related to failure of amalgams secured to teeth with steel pins. I met a dentist in the student union building at the University and after a little chat asked what he was studying. He was investigating the failure of amalgam fillings. I asked him what the material was like and he said it had a high compressive strength and a low tensile strength, very much like concrete. I asked him if it could be a tensile fatigue failure generated by the tensile stresses at the bearing of the amalgam and the steel pin. Did some FEM models using a 3D FEM program I had written and then we did additional studies using plastic and polarised light. Was fun... Reinforcing is another issue for bearing. The ACI and CSA codes allow the increase in bearing stress just due to the confining nature of the loaded concrete with a small area loading a large area of concrete. Dik
  3. I'm not sure about ACI and CSA guidelines, although it seems obvious that if there is compression stress spread there is tension which should be carried by reinforcement. Anyway, EC2 allows increase of up to 3 times of the design strength of concrete for crushing and spalling resistance (first potential failure mechanism) of the "partially" loaded area but the designer also needs to check the area for bursting (second potential failure mechanism), which should generally be done by strut-and-tie design of adequate reinforcement. If this reinforcement is provided and bursting is not the governing failure mechanism, then one can take advantage of the increased crushing/spalling resistance. Not particularly allowed by EC, but "FIB Model Code 1990" (which is basically the basis of EC) allowed potentially increased bursting capacity for bulging compressive struts (which basically is this "partially" loaded area case where compression stresses spread out in a larger area) which are not adequately reinforced and the capacity (allowable bearing pressure) was influenced by the geometry of the bulging strut and the design tensile strength of the concrete. Of course this method could only be used for regions which where not expected to crack in the life of the structure because of any other influences/actions like shrinkage, etc. If cracking was expected and no bursting reinforcement provided then the bearing pressures allowed would be (by EC) around 53% of concrete compressive design strength.
  4. Hi engineers, There are tabulated data in "EC 1992-1-2 General rules. Structural fire design" for columns, but only for braced ones. What about unbraced ones? Any suggestions?
  5. Can you kindly give a download link? Many thanks
  6. Excuse me but, how do you save a calculation in Gala Reinforcement? Don't know how to do that... :/
  7. Yes, it's available in English.
  8. Unless you really need the compression steel for either flexural capacity or for limiting long/short term deflection it is not common to include its contribution (with the exception of forensic work, where it may be an issue). There are numerous engineering texts that provide an analysis of a doubly reinforced section. Dik
  9. I'm way past the limit and don't know how I got there; I cannot remove uploads to free up some space. Dik
  10. Can you find more recent publications? Unless these papers are exemplary, they are in excess of 30 years old. Dik
  11. Last week
  12. Can't find it in Research Gate. I think these will be available on some good academic institution's library. so, if someone find, please scan & upload it .
  13. Try searching them at Research Gate. You might find them there.
  14. Hi . I need following two papers for my research on bridge design . If anyone have the papers please help. i) The buckling of slender bridge piers and the effective height provisions of BS 5400, Part 4" by P. A Jackson, Cement and Concrete Association, London, June, 1985. ii) Morice, P. B. and Little, G., "Load-Distribution in Prestressed Concrete Bridge Systems," The Structural Engineer, London, March 1954, Vol. 32, pp. 83- ill.
  15. Reinis: ACI and CSA codes allow for an increase in bearing capacity based on the overall concrete area and the area loaded; this is independent of the steel reinforcing. Dik
  16. Eurocode allows for up to three times the design compressive strength of concrete if you provide adequate reinforcement. Cheers
  17. It's a good idea and common to many jurisdictions. Spacing can be closer, but, should only be undertaken if agreed to by the geotechnical consultant on the project. Dik
  18. As Reinis noted... need more info. Are you referring to bearing capacity, either limit states or working stress? There should be an increase in the compressive strength for concrete if the concrete bearing is confined. Don't know if Eurocodes allows for this increase, but, it is common in many jurisdictions. Dik
  19. Can the beam be post-tensioned with conduit as a single continuous beam? Precasting with straight strands can be done with different strand patterns for different loads/spans. Some spans can even have the strand depressed towards the bottom fibre. Precasting gives the advantage of quality finishes and minimal member sizes. Quantity is a lesser issue, the Montreal Olympic Stadium was precast, and I don't think there were two pieces that were the same (this was a mistake IMHO) and it was a terrible detail design project. Composite design of HSS, concrete filled, columns is a good solution for some applications. Check with CIDECT for information including improved fire resistance rating. There are some applications where a fire resistant coating/enclosure is not required. Dik
  20. No - you need to report them!
  21. Are these kind of posts legal?
  22. You need the longitudinal bars to create the three dimensional truss system that will resist the torsional moment.
  23. Hello! Is there any way to increase the limit of image upload? What is the best way to make an image smaller? How do you do it? Thank you all!
  24. That would be very complicated. I think I would keep the column reinforcing and lap it inside the foundation. I belive that any additional capacity of the foundation (any additional capacity of resisting bending moments) would be an extra contribution to the lateral resisting system of the structure. It would rather be a conservative approach. Do you agree?
  25. One way would be to make a steel connection with a pin (big diameter bolt). You can attach a steel base via welding to the reinforcing steel...
  26. Well, I totally agree with you if we are talking about steel structures (to make a pinned base I put 4 bolts inside the flanges of a H section). What about concrete structures? How do you materialize, or at least try to, the pinned connection in a monolithic concrete structure? How do you lap your reinforcement if you want a "connection" with no moments?
  27. Normally I try to avoid fixed foundations as it makes them much bigger (and costly). However, it depends greatly on the level of static equilibrium you need and the configuration of your structure. You can have pinned bases but this will largely increase the bending moments in your nodes and/or the efforts in your bracing system. If you use pinned bases pay attention to the bracing in both directions, specially if you don't have specific horizontal loads.
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