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Re: chevron bracing frames

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Dave Anderson wrote:

> hi
>   Is anyone knows  if the beam column connections hase to be
>   moment connection or not
> the UBC section 2211.8.4.1 for chevron bracing
> #2 -states that the beam intersected by chevron braces shall be
> conttinuous between column.
> plus if there is no moment connection when you eleminate the braces
> the structure become unstable because you have no moment connection at
> the column base
>
> thanks for replay in advance
>
> D.A.  P.E.

I'm assuming that your are dealing with an ordinary concentrically braced
frame and not a special concentrically braced frame or an eccentrically
braced frame.

The short answer is no, you don't have to design as moment connection.
However; I believe that the blue book advises that you try to provide some
sort of moment frame backup system, even if it is does not have the
strength to be fully redundant to your braced frame.  We have found that
drag forces to the frame can be very high, and we often create a pseudo
moment connection to give us our drag capacity.

The bit about the beam being continuous between columns is because they
want the beam to be able to carry gravity loads with the braces removed
(special concentrically braced frames have even stricter requirements).
What they don't want you to do is something like cutting you beam in half
at the center of the span and relying on the braces to take the vertical
loads for you.



Stan Johnson, PE.

1.  Where the braces intersect the beam from below, the beam must designed
to be able to take gravity loads without the braces being present