Minimum Radius - PT Systems

Hi There,

I have a question about RAM Concepts usage of minimum radius parameter when it comes to post tension cable curvatures (dealing mostly with flat ducts containing 12.7mm/15.8mm strand tendons here in Aus).

We have noticed that for same radius we get error in RAM Concept but we do not get that error in RAPT. For example, RAPT recommends minimum reverse curve radius of 2500mm with default being 5000mm. I have set the curve radius to match that of RAPT i.e. 2500mm but tendon radius errors is still persistent. Could you please explain why for the same radius the profile is acceptable to RAPT but not to RAM Concept. See below (note RAPT is allowing this profile on 5000mm radius):

Quick run of 1m deep beam with 9m span

 

Room for improvement: Sean Smith mentioned this before but could you guys make it so that we can at least see the radius of tendons on top of them like we can see other properties of tendon. The other thing is can you add a function that with click of a button gives you the lowest allowable low point based on minimum radius. 

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  • Thanks Seth for the prompt response.

    Assuming 2500mm radius with 10% inflection point ratio, now the results should match, as in no "radius error" from RAM Concept should occur right?



    I just want to understand if both software are using 2500mm minimum radius why one is giving error and the other is not?

    Thanks Mate

  • I can't be totally sure how RAPT calculates this, but your last image looks like a parabola with a flattened top which differs from our assumption. Here are the calculations for your 9 m example. 

    Variable Value Units Comment
    L 4500 mm, in from A to B (half-span)
    x 0 mm, in from A
    i 0.2 inflection point ratio
    iL 900 mm, in
    a 0.000218272 1 parabola coefficient (x before IP)
    b 5.45679E-05 0 parabola coefficient (x after IP)
    Ya 942 mm, in
    Yb 58 mm, in
    P 884 mm, in
    y' 0 parabola slope
    y" -0.00043654 parabola curvature
    r -2290.72398 mm, in parabola radius of curvature

    And here's the output from the CalcLog confirming the same value: