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Recent content by Ilight

  1. Ilight

    Plastic hinge in reinforced concrete

    I thought plastic hinge is the point when the member doesn't take anymore moment however it can still undergo rotation with excessive moment being applied. When the steel reinforcement yields (strain at 0.0025), it is in a plastic state, but it can still take an increased moment. Which leads me...
  2. Ilight

    Plastic hinge in reinforced concrete

    Hey everyone: So for typical reinforced concrete member, is there a way to calculate the moment at which plastic hinge will form? I've heard that it is similar to flexural moment, with strain in extreme fibre being 0.003. Thank you!
  3. Ilight

    Rafter design in portal frame

    Hmm upon further research, I found out that if the bottom flange doesn't have any restraint, then the buckling length for the analysis would be the rafter length. If I had Fly brace for twist and lateral rotation restraint, would the buckling length become shorter? I know that the axial force...
  4. Ilight

    Rafter design in portal frame

    Hey everyone: How do you consider the buckling length of rafter under axial compression? Would it just be the distance between purlins multiplied by a factor of 0.7 ~ 1? I'm trying to work out the combined action of axial force and bending moment on rafter, however, somehow SpaceGass decides...
  5. Ilight

    AS4100 Beam design confusion

    Hi Agent666 By adjacent segment, do you mean for example in F-P-L segment, if F-P has full lateral restraint, I can take P section as rotationally restrained? Cheers
  6. Ilight

    AS4100 Beam design confusion

    Hey everyone: So I've always been told to assume the rotational restraint factor kr as 1 for the effective length calculation. Then I had a look in AS4100, apparently it is associated with lateral rotation of the member. My question is how are these restraints provided? In C5.4.2.3, it seems...
  7. Ilight

    Transfer length for pre-tensioned

    Hey everyone: Let's take 12.7mm low relaxation strand for example, in the PCI code, for effective prestress at transfer, they have adopted 170ksi which roughly equates to (0.75*270)*0.85, assuming the total losses are 15%. However on the second graph, the effective prestress they've taken is...
  8. Ilight

    Long term and short term shear strength from CU test

    Hi LRJ So for the undrained shearing stage in CU test, it would mean that the pore pressure at failure actually equals to U=U0 + U(from applied vertical load)? But that counts as short term effect right? I don't quite understand how it suppose to resemble long term effect (if you could refer...
  9. Ilight

    Long term and short term shear strength from CU test

    Thankyou for the reply GeoEnvGuy So by undrained failure, you're referring to the short term state when the overburden pressure is taken by the pore pressure right? Which is what CU test resembles, since in the shearing stage the drains are closed. But I don't quite understand where the long...
  10. Ilight

    Long term and short term shear strength from CU test

    Hey everyone: For a typical CU triaxial test, I can't seem to get my head around why the effective failure envelope corresponds to the long-term drained effect for a clay sample. Let's say the confining stress is Sigma 3 and the deviatoric stress is DeltaSigma, hence total stress sigma1 =...
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