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Re: What about iron balusters and guardrails?

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Re: Guardrails and Handrails

This is a topic that is not too complicated, but is seldom well-understood
by structural engineers (at their peril).

Guardrails and handrails are two different items, which have two different
sets of structural design requirements.  Different codes vary somewhat in
the specific forces, but the concepts are all similar.

GUARDRAILS are required where there is a sudden change in elevation greater
than 30" (typical value).  Examples are balconies, decks, retaining walls
(if there is a walkway along the top), mezzanines, and the open sides of
stairs.  (The three exceptions I know of are the audience side of a stage,
trap doors in stages, and loading docks.  Try to imagine these with a
guardrail....)

There are two distinct components of the guardrail: the top rail, and the
portion between the floor and the top rail, where the balusters go (or maybe
it is solid).  The top rail of the guardrail is not the same as a handrail,
except in special circumstances (see below).  The "top rail" may not even be
a rail in the true sense.  Picture a solid glass guard with an integral rail
at the top.

There are architectural requirements with respect to the minimum height of
the top rail of the guardrail and the maximum size sphere that can fit
through the spaces in the baluster system (typical is 42" high for top rail
(36" for some residential) and a max 4" sphere through the spaces).  There
are NO requirements for grippability of the "top rail", unless it is ALSO a
handrail (see below).

There are structural design requirements for the capacity of the top rail
and the baluster portion to resist applied loads.  Typical is a concentrated
load applied in any direction to the top of the guardrail, OR a uniform
(line) load horizontally to the top of the guardrail, and a uniform (areal)
load on the entire baluster section.  Typical for UBC is EACH of the
following, considered INDEPENDENTLY: 20 plf (residential) or 50 plf (all
others) on the top of the guardrail;  200 lbs in any direction on the top
rail; and 25 psf on the balusters.

HANDRAILS are required on stairs and ramps for gripping with the hand.

There are architectural requirements with respect to location and size of
handrails:  whether one or both sides of stairway (or ramp);  height above
ramp or nosing of stair treads, distance from wall, min and max sizes of
grip, and extensions beyond the end of stair or ramp.  Typical are between
34" and 38" above nosing (to center), 1.5" min space, 1.25" min and 2" (?)
max diameter, 12" extensions (except residential stairs).  Residential only
requires handrail one side (?), commercial two sides plus intermediate
handrails where stairs are wider than 88" (?) etc.

There are structural design requirements for the capacity of the handrail to
resist applied loads.  Typical is a simultaneous horiz and vert concentrated
load at any point along the rail, 50 lbs each per Scott (?).

In some cases, the top rail of the guardrail and the handrail are the same
thing.  This occurs on some residential stairs where the architectural
requirements allow the guardrail height to be the same as the handrail
height.

My 2 cents.  I invite corrections, arguments, and criticism.

Mark Swingle

------------------

On 29 July 00 Francisco Duarte wrote:

<do we need to design the iron balusters and railing systems? If so where do
we get info in terms allowable values.
Are there any text books that have pretty much standard construction details
for different kinds of railing and guardrail systems.

<Same thing goes for stairs. 
any comments will be appreciated

<Mil Gracias,
<(thank you)

<F.D. (E.I.T)

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