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Single or continuous span?

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  1. #1
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    Default Single or continuous span?

    I hope someone can shed a bit of light on this...

    Is a joist that sits across two bearers, overhanging the bearers for about 200mm, single or continuous span (see attachment)?

    When I was doing calculations with DIY Deck Plan Calculator - Stumps, Bearers, Joists and Boards, it seems that the software would consider this arrangement a continuous span.

    For instance for a 1510mm span (that remains constant) when the joist ends flush with the bearers, the calculator requires another support (bearer) in the middle. It seems that the distance is too large for a single span for the chosen timber profile, so a continuous span is required and it adds another support in the middle. This result seem to agree with the figures in single span tables.

    Just extending the joist past the bearers (for not more then 200mm), with no changes to the span, the calculator allows for larger span and no additional support in the middle is required. The result becomes comparable with the figures in continuous span tables.

    I don't understand why extending the joist past the bearers allows for larger distance between the posts? Can someone explain the logic behind?

    Thanks.
    Attached Thumbnails Attached Thumbnails case2.jpg   case1.jpg   span.jpg  

  2. #2
    4K Club Member ringtail's Avatar
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    Default

    Its wrong. Single span is single span. I just did the exercise on the hyne program and it gives the same timber dimensions regardless

  3. #3
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    Default

    Thanks for the reply. So basically I can use the single span table and work out the details.

  4. #4
    4K Club Member ringtail's Avatar
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    Yup. Single span members should always be bigger ( or span less) than a continuous member. Are they the span tables in the forum or something else ? If you dont have access to AS1684 or Hyne use the forum tables not something dragged of the net ( if you know what I mean )

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