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  1. george69

    Von Misers criterion or Principle stress?

    Apsix- great work !! That is the "trump" card I was looking for!!!
  2. george69

    Twin beam lateral restraints at top flange

    Hi apsix Actually I I have startted the model in Strand 7 and will be adding in a imperfection. I'm going to have a re-read of Trahairs book in the morning. CHeers
  3. george69

    Unconsolidated undrained test

    Thanks GeoPaveTraffic The snapshop analogy is a very good way of thinking of the Q test! Are you saying the consolidated undrained test looks at an envelope of consolidation stresses? If I am understanding you correctly, after plotting the mohrs circle, and assuming ideal conditions for...
  4. george69

    Unconsolidated undrained test

    A further query to my question and it may be related: For a Consolidated Undrained triaxial test, the point at which the sloping tangent line intersects the vertical shear stress axis -> is this termed "cu" or "c"? If it is "cu", would this be the same magnitude for "cu" if the testing was...
  5. george69

    Unconsolidated undrained test

    Hi Can some please explain to me in basic terms why the total stress cohesion "c" measure from consolidatd undrained triaxial test is always smaller in value than if measured by the unconsolidated undrained method which gives "cu" Why are the "c" and "cu" different anyway if they are both...
  6. george69

    Twin beam lateral restraints at top flange

    Giving it some thought I think I have got a way to prove or disprove if the truss works by using an analysis program. Creating the model: 1) Create the truss(say a plan view of it). 2) Model the top flanges of the 900WB as the chords. 3) Model the web members (I have angles for bracing) 4)...
  7. george69

    Twin beam lateral restraints at top flange

    HI all Not sure if this is worth anything and I have yet to read it. Unfortunately from Googlebooks so it is not complete. May trigger some thoughts but it would appear to me that the forces could act in the same direction. Book is STeel Structures: Design and Behaviour by Salmon Johnson and...
  8. george69

    Twin beam lateral restraints at top flange

    BA retired OK - FYI In this instance there is no lateral wind. Just pure vertical point load at midspan. As you've seen from the AS4100, it specifically refers to "THE lateral restraint" which I take to mean individual elements need to restrain 2.5% of flange force taken laterally. But it does...
  9. george69

    Twin beam lateral restraints at top flange

    apsix Thanks for posting the AS4100 reference. And you are correct, if the restraints are closer, then you don't need to design them for the full load - obviously a pro-rata and easily done. The question, which I believe BA correctly answers via Canadian approach, is that the "restraining"...
  10. george69

    Twin beam lateral restraints at top flange

    Thanks for your response. BAretired is your suggestion that the global truss effect is ignored? I have attached a rough sketch to elaboratehttp://files.engineering.com/getfile.aspx?folder=4e094fe0-ffd9-437b-b511-e0b2ac095810&file=DOC050310.pdf
  11. george69

    Twin beam lateral restraints at top flange

    HI all I have 2-900WB simply supported beams spanning 18m. the beams are 1100mm apart. There is a large concentrated load in the middle. There is top flange K-bracing that tie the beams together. The nodes that for this "truss" are at 1m centres. They have the same bending moment at midspan...
  12. george69

    Bottom flange of a monorail

    The AS1418 is the most comprehensive and accurate. The bottom flange capacity "Tf" formula was determined from combining local bending stresses with longitudinal bending stresses by Von Mises criteria. The "Tf" formulas accuracy was verified in the early 70's by BHP testing a series of I beams...
  13. george69

    Von Misers criterion or Principle stress?

    Spot on apsix!! Thats the page that I was referring to. Although no code should allow designing to full yield, going to 90% in the VM criteria is close and vastly different to satisfying 0.66Fy for principle stresses. Personally I think that the code is vague and should be prescriptive on...
  14. george69

    Von Misers criterion or Principle stress?

    hi apsix Sure. AS1250 is the working stress code. I think it is clause 5 that stipulates the principle stress limit. However, the VM yield limit is referred to in the Source book for the AS1250. The Source book is a commentary on the 1250.
  15. george69

    Von Misers criterion or Principle stress?

    Hi BAretired and thanks for your comments. The issue is not so much the equations, or what the euqations reduce to. It;s really about the factors of safety. s1<0.66Fy(for Principle stresses) versus s1<Fy/1.1(for VM criteria) as a code requirement. Thanks to all who answered this query - Big...
  16. george69

    Von Misers criterion or Principle stress?

    Omairzali I see your point and yes, satisfying 0.66Fy automatically satisfies VM.. BTW, in my example, it was a simplistic case looking at midspan, where shear is 0. Just to emphasis my case with the longitudinal bending stress Thanks again for your input and help!!
  17. george69

    Von Misers criterion or Principle stress?

    omairzali. Agree with your comments. So in short are you saying that both criteria need to be checked all the time regardless of stress condition. Remember that for a simply supported beam, as per my example above, has only one stress(bending in long direction). I gather from your comments...
  18. george69

    Von Misers criterion or Principle stress?

    Actually no. The case I am referring to is a simplistic case where the shear stress is 0. An example would be a simply supported beam with UDL on it. Thus, at midspan, the only stress is the longitudinal bending stress. The question is which code provision to use and is best representative of...
  19. george69

    Von Misers criterion or Principle stress?

    Hi All My question is in relation to Von Misers Yield stress criterion vs Principle stress limits. If I have a simply supported beam with a point load in the middle, should the longitudinal bending stresses in the beam be checked to priciple stress limitations or to Von misers criteria. The...

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