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 MIL-HDBK-1038
available in lengths up to 70 feet.) The splices are made with flat plates on
both sides of the upper T-section webs. The lower T-section end must be positioned
to minimize the gap on the running surface for smooth crossing by the wheels. The
splices must be located directly under the support members.
Patented track is available in curved sections with any radius of
curvature down to 48 inches. This fseature permits the patented track to be laid
out in the form of closed loop circuits. (Electric power for hoist/trolley units
can be delivered through matching rigid conductors attached directly to the
patented track.) I-beam track can be bent to a 20-inch radius.
4.1.7.1
Runway Suspension Systems. Depending on the available headroom in the
building, the runway suspension system may be rigid or flexible. The rigid
suspension system has the upper flanges of the patented track bolted directly to
the building structure or to interposed solid spacers. These joints usually
include shims to obtain the required levelness. The flexible runway suspension
systems support the patented track on vertical alloy steel rods with threaded
ends. The rods are threaded into self-aligning gimbals or ball-and-socket
fittings, which are bolted to the building structure and the patented track.
Additional lateral and longitudinal tie rod braces are usually installed to limit
the sway of the runway. Flexible suspension systems for cranes with rigid end
trucks normally have one patented track installed without lateral braces to avoid
travel truck binding due to minor gauge variations. All flexible suspension
components are standard commercial items.
Suspension of curved sections of runways requires particular attention to
minimize the introduction of lateral bending moments (twisting) of the patented
track.
4.1.7.2
Extensions and Transfer Sections. The bridge girders may extend as
cantilevers beyond the end trucks to extend hook approaches or to facilitate the
transfer of the hoist/trolley unit to an adjacent crane or spur track. With such
arrangements the girder lower flanges must be brought into close alignment and the
gap between them must be held to a minimum. Interlocks are required to engage and
lock the girders in alignment during hoist/trolley transit. In cases where the
opposite bridge girders cannot be brought into close proximity, a short transfer
section is installed to span the separating distance.
On cranes whose hoist/trolley units transfer directly to another bridge
girder, the end trucks should be located near the ends of the bridge girders to
minimize the relative deflections at the gap. Also, the adjacent runway tracks
and the transfer section should be supported from a common structural member.
This will help to maintain the alignment of the lower flanges for smooth wheel
transit.
4.1.8
Cantilevered Booms. The booms of cantilevered cranes may be of any form
or cross section box, single web, or monorail. Because of the wide variety of
boom configurations and their supports, there are no established designs or
analyses for them. Each design is unique in some aspects and must be designed in
accordance with the applicable requirements of the structural code. The same
applies to the boom support structures (pillars, wall brackets, and vertical
frames) and connections. These booms are relatively short and therefore do not
require any camber; however,
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