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Re: ANGLE IRON LOAD/DEFLECT QUESTION

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Matt,

        Excuse me if I seem to be overly candid with my comments which
follow.  I'm really not trying to be rude or condescending, only
helpful.  You seem to be very inexperienced with grating in general and
in what you are trying to do.  Let me try to enlighten you.

        There are a great variety of grating products.  The most common
is bar grating, which is available in several thicknesses, the most
commonly used being 1.25 inches.  "Grip Span" type gratings, which are
made from cold formed sheet metal are also fairly common; common depth
is in the order of 3 inches.  Other types such as fibreglass reinforced
plastic are also available but I have never seen them used.  All of the
gratings that I have had experience with span only in one direction;
their strength in the other direction is only enough to hold the grating
together.

        Bar grating is manufactured in sections in the order of 4 feet
wide by  40 feet long.  It is cut and banded as required.  Typical spans
are three to six feet.  Spanning 25 feet is completely out of the
question!!

        "Grip Span" grating segments are usually about one foot wide by
the required length.  Spans in the order of ten or twelve feet are
achievable.  Spanning 25 feet seems to me to be unreasonable but not
necessarily impossible; I just haven't seen or even heard of it being
done.

        Designing a grating floor is fairly straight forward:

1.)    Determine the appropriate design loading.  You should find these
in the design documents for your project or in the applicable building
code for the site location.  (The most likely live loads are 50 p.s.f.
or 100 p.s.f. but something else might be appropriate)

2.)    Obtain one or more manufacturer's grating catalogues.  The
load/span tables contained therein are needed to design the grating.

3.)    Layout a trial support beam arrangement.  Suggested layouts are:
six spans of 4'-2"; five spans of 5'-0"; or four spans of 6'-3".

4.)    Select the appropriate grating for your layout and size the
support beams.  Note: use the same grating for the entire job; do not
mix grating types.

5.)    Calculate the cost (or perhaps the material weight) for the
design.

6.)    Repeat from 3.).  Consider designs which involve spanning in the
other direction.  Select the most economic design, then discuss it with
your Mentor.

        You may be able to use an L to contain the grating or to secure
it to a structural member but you will not be able to use it to span and
carry the load.  In any case the L must be dimensionally compatible with
the grating.  For instance, if you have 1.25" bar grating the INSIDE
depth of the L must be 1.25", hence, the L would have to be
1.5x1.5x0.25, not 0.125" thick.

        I don't know if this is enough to help you.  If not perhaps
others may be able to add to it.

Regards,

H. Daryl Richardson

Matt Wright wrote:

> I have some questions regarding load. I have a series
> of 25-foot spans that need to support an aluminum
> bar-grating platform and light pedestrian traffic. The
> bar grating will not be welded to the frame, it needs
> to be removed for cleaning. We are trying to find the
> material which will allow us to span the length with
> the fewest number of floor-to-platform supports
> possible(none at all if it is possible). We would like
> to use a 1-1/2"x1-1/2"x1/8" angle steel. If it is
> possible to span the entire length with a single
> length of angle and no intermediate floor to platform
> vertical support, that would be best. I am also
> wondering about flexing/bouncing, which needs to be
> minimal.
>
> Please let me know what advice you can give. Great
> threads on this board, by the way.
>
> Thanks,
> Matt Wright
>
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