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Re: Residential construction-hip beams

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Another consideration in "rafter" type framing is the location of the structure and
the superimposed loading.  I work in an area of high snow loading.  The rafter system
is somewhat like a truss if it were to be designed.  the collar tie or the ceiling
joists must me capable of transferring the tension from the rafters like the bottom
chord of a truss.  With heavier loads the connections at the rafters to the collar
tie or ceiling joists/top plate can be very difficult if not impossible to make. with
another problem of connecting to the ceiling joist system  when the ceiling joists
are perpendicular the the rafter span.  Another thing to consider is the height of
the collar tie.  The higher the collar tie the more moment that is induced into the
rafter which may over stress the rafters.  In either condition the rafters (like the
top chord of a truss) are in a combined loading situation.

Joseph R. Grill, PE

"Barry H. Welliver" wrote:

> I think we simplify the hip and ridge beam design in residential engineering
> because we don't have much else to base design on. If there were sufficient
> evidence (other than hearsay) that actual loading to ridge and hips were a some
> smaller percentage than full tributary area, I think we'd listen. Trouble is, we
> don't have much else than our commonsense and practical experience to make a case
> otherwise.
>
> Other factors, in my opinion, which would lead to justification of lesser loading
> to hip beams would be:
> 1.    plywood roof sheathing (and its ability to form deep beam segments).
> 2.    ceiling ties (at least partial)
> 3.    diaphragm size and top plate continuity.
>
> Now valley beams..... that's the exact opposite problem and I tend to be
> extremely conservative in loading there.
>
> Barry H. Welliver
>
> Roger Turk wrote:
>
> > Ridge boards are non-structural because they simply provide a bearing surface
> > for rafters on *each* side of the ridge board.  The rafters are tied together
> > either with collar ties or by ceiling joists.  The ridge board is incapable
> > of providing vertical support to rafters and only provides a bearing surface
> > so that slight misalignment of rafters on each side can be tolerated.
> >
> > On the other hand, rafters connecting to hip beams are not tied together,
> > either by collar ties or ceiling joists, and, IMO, must be supported by hip
> > beams and the hip beams must be capable of supporting the vertical loads.
> >
> > Hope this helps.
> >
> > A. Roger Turk, P.E.(Structural)
> > Tucson, Arizona
> >
> > Domenic DeAngelo wrote:
> >
> > >>I would like to know how engineers address hip beams in residential
> > construction. Are they carrying members or similar in nature to ridge
> > boards?
> > I am of the opinion that they are non-structural and do not require to be
> > designed.<<
> >
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