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Handbook: 22 of 287
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CANOPY PLATES AND FRAMES.
1. For all dimensions, calculate each prism
light an even four (4) inches, adding one-half (½) inch all around
for iron border of prism plate.
2. All canopy prism plates containing over five
(5) square feet should have intermediate supports, so that no area of
more than five (5) square feet of plate will be unsupported.
Bars may be glazed into prism plates at intervals
to receive supports from above or beneath. (See detail sheets of
canopies.)
Even when stiffening bars are used no single prism
plate should exceed fifteen (15) square feet in area.
3. The iron border is one-half (½) inch
wide by one-quarter (¼) inch thick.
4. The sight opening of frames to which the
prism plate border is secured should clear prisms one-sixteenth
(1/16) inch all around. See detail sheets of canopies.
5. Provision should be made in designing canopy
supports for allowing an adjustment, at the building, of at least ten
degrees in the slope or pitch of frame carrying the prism plates. This
is allowed for in examples shown, either by shifting the point of support
at wall line or on canopy frames, or by increasing or diminishing the
length of supporting members.
6. The following schedule of structural iron
should be used for canopy frames:
| For |
spans |
up to |
36 |
inches, |
1×1×1/8 |
Angles |
and |
Tees. |
| " |
" |
" |
48 |
" |
1¼×1¼×¼ |
" |
" |
" |
| " |
" |
" |
60 |
" |
1½×1½×¼ |
" |
" |
" |
| " |
" |
" |
72 |
" |
1¾×1¾×¼ |
" |
" |
" |
| " |
" |
" |
84 |
" |
2×2×¼ |
" |
" |
" |
| " |
" |
" |
96 |
" |
2½×1½×5/16 |
" |
" |
" |
All the above dimensions are in inches.
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