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Thread: Scaffold stability check

  1. #1
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    Default Scaffold stability check

    Good afternoon gents,

    a quick question; when doing stability check especially for temporary roofs is there a simplified way to do a sway brace check apart from Structural Engineering Software?

    What other stability checks would be required apart from overturning?

    Regards!

  2. #2
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    For temporary roofs (and most other external scaffolds) you first need to calculate the wind load using EN 1991 or TG9:12. You then need to ascertain the most onerous load condition for each direction. Once you have established the wind loads,along with snow, live and dead loads, you would then check (as a minimum)
    1. Overturning as a unit (if the support scaffold to roof connection is strong enough and the scaffold is free-standing).
    2. Ledger or transverse brace loadings
    3. Tension and compression in the supporting standards - anchors or kentledge may be required if free-standing.
    4. Tie loading (if any)
    5. Uplift at roof to scaffold connection
    6. Gable end plan bracing (if any)
    7. Longitudinal bracing loadings
    8. Tension/compression in the standards and/or overturning in the longitudinal direction
    9. Roof beam check against uplift (wind) and against downward forces (snow, live load, dead load)
    10. Roof connection check
    11. If using a duopitch roof in particular, you also need to check the horizontal forces induced by the roof angle which add to the tie or overturning loads.
    TG9:12 recommends structural analysis software and it is by far the most accurate and safest way to design roofs and temporary buildings, especially duopitch roofs. For simple monopitch roofs a hand calculation may be sufficient but would still need to include all of the above.

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    pride2iceman (10th November 2017)

  4. #3
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    No.

    You can do simple analysis if it is statically determinate but still not worth the effort. Stick it in a wireframe model (something like Cads / Robot) and it will do it all for you - you just need to be sure you know what you're modelling and how to model it as **** in = **** out and few people recognise when they get an absurd output.

  5. #4
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    I agree with ID that structural analysis is the best method for long span duopitch roofs or more complex type temporary buildings but some experience in using the software is vital to ensure you get the correct results. One of the main pitfalls when designing scaffold using software is the anchorage (or lack of) for the standards connecting to the ground; the simplest way to model is to pin all the standards to the base to represent anchors to the foundations but this is often not the case with scaffolding. The software should allow you to create compression only members which is one way of dealing with this if you are using kentledge for example. For smaller less complex monopitch roofs, temporary buildings and other sheeted scaffolds, hand calculations are far quicker and just as accurate if performed by an experienced engineer.

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    Nick-CDS (1st February 2018)

  7. #5
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    I like Robot for this kind of thing, personally. I find it quite user friendly compared to some of the other FEA software out there. Even though I like the program, I'll do a few hand calcs just to make sure we're both in the same ballpark.

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    biffo0911 (3rd February 2018)

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