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Steel Framing for Elevator Shaft

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Fellow engineers,

        I would like your comments regarding the re-use of steel
elevator framing for an elevator shaft in a 1912 vintage building.

        The structure is a reinforced concrete structure four stories
plus a full basement.  The building footprint is 60' facing the street,
by 100' deep  The construction consists of one way concrete slabs
(spanning about 12') with beams (spanning from 12' to 20'); columns are
about 18" plus in dimension.  The perimeter wall is solid brick 11" plus
in thickness with a substantial amount of window openings on three
sides; the back end wall has only one man door opening, no windows.  The
storey heights (floor to ceiling) are basement, second, and third floor,
11'; main and fourth floor, 14'.  The building was originally designed
for six storeys and two elevators but the last two floors and the second
elevator were never constructed.  There are no signs whatever of any
structural distress in the building.

        The elevator (just removed this past week) was a cable supported
manual operated contraption in working order (but only barely) that
occupied only one half of the elevator shaft.  The support structure for
the elevator shaft consists of four L6x6x0.375 secured at every floor
with horizontal channels in between floors.  There are also two vertical
L5x5x0.375, one back and one front, which would provide a demarcation
between the two elevators.  There is no diagonal bracing.  All of the
connections are bolted and we would continue to use bolted connections
rather than try welding to that old steel.

        There are three objections to installing a masonry shaft for the
new elevator: schedule; cost; and available dimensions of the slab
opening.  To use a masonry shaft we would either have to stop and
restart the masonry at every floor, find a way to reduce the wall
thickness to 4" (at least at the floor openings), or cut the floor
openings larger (which would involve cutting away the side of some
beams).  Reusing the existing steel addresses all of the above concerns.

        The new elevator will be hydraulically operated and will
transmit all of the vertical loading to the elevator pit floor, whereas
the existing elevator transmitted the vertical loads to the four L6x6.
The rail loading will be horizontal only, of magnitude 301 pounds, with
a deflection limit of 1/32".  I can accommodate this 1/32" deflection
limit and take care of the fire protection requirements required by the
building upgrade (with only a little squirming).

        Calgary design conditions are: wind about 85 miles per hour for
open exposure (this building is in the centre of the city); earthquake
used to be 0 increased to 1 a few years ago (compared to California this
is trivial).

        My question: do you know of any problems with reusing this
elevator supporting steel that I may not have foreseen?  I haven't seen
anyone use this type of elevator support structure on new buildings and
there may be good reasons why not.

        Thanks for any comments you may choose to make.

Regards,

H. Daryl Richardson


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