ETL 1110-2-534
30 Sep 94
basically the same for all mounting arrangements
w
= railing load per unit length
and is calculated as:
K
= 8 for one or two spans
P
h
fapplied
K
= 9.5 for three or more spans
d
For all loadings, the applied bending stress fapplied is
for the mounting arrangement depicted in Fig-
calculated as:
ure A-3a, and as:
Mapplied
fapplied
P
(h
a
d)
S
fapplied
d
and compared to the allowable bending stress fallow
as discussed in paragraph A-2c above. The applied
stress should always be less than the allowable
stress.
h.
Anchorage analysis.
(1) While all of the above calculations may
show a guardrail system to be structurally safe, the
system will still be only as strong as the anchorage
to its supporting structure. Whatever the supporting
structure -- metal, masonry, or wood -- attachment
procedures are much the same; only the type of
fastener will vary. A railing can be mounted on the
fascia or stringer of a platform or stair, can be set
into the floor or stair tread, or can be mounted on
the floor or tread surface with a mounting fixture.
Figure A-3. Guardrail mounting methods
(2) When railings are set into concrete or
masonry floors or treads, the post receiving holes
for the mounting arrangement depicted in Fig-
should generally be at least 13 cm (5 in.) deep in
ure A-3b. A safety factor of 1.65 should be applied
order to provide ample post support. The edges of
to these values. The applied pullout force is then
the holes should be located at least 9 cm (3-1/2 in.)
compared to the allowable pullout force (supplied
from the edge of concrete or masonry. The ends of
by the manufacturer), which is calculated as:
the aluminum posts should be coated with bitumi-
nous paint, methacrylate lacquer, zinc chromate
primer, or other suitable coating to protect against
fallow
F
n
accelerated corrosion caused by contact with con-
crete, grout, or dissimilar metals. For railings
where n = number of fasteners in line. Because of
mounted on the surface of the floor or stair tread,
the uneven quality of concrete, it is recommended
either lateral bracing is required or a heavy-duty
that a safety factor of 4 be applied to the allowable
floor flange, designed to withstand the required
pullout force. However, many manufacturers have
loading and to support and reinforce the post, must
already applied appropriate safety factors to their
be used.
recommended pullout values, and additional safety
factors may not be necessary. The manufacturers'
(3) Required fastener capacity can be deter-
recommendations for anchor embedment length and
mined by computing the moment about a fastening
hole edge distance should also be carefully checked.
or support and comparing to the allowable bolt
pullout force, which is listed by the manufacturers
of the fasteners. The applied bolt pullout force is
A-7
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