MIL-HDBK-1005/6
Section 4.
PORTAL CRANE TRACK REPLACEMENT CURVE ALIGNMENT
Guidance. NAVFACENGCOM Headquarters has a computer program system
4.1
and the accompanying documentation and application manuals, entitled TRACKS,
available for use on the NAVFAC Computer Network for replacement track curve
alignment. Although it is not mandatory to use this program for replacement
design, its use is highly recommended due to its speed, accuracy and cost
effectiveness. Since this program will play an important role in most track
rehabilitation, the criteria of this section will be guided by the information
needs of the computer procedure. For information and assistance in the use of
the TRACKS program, contact NAVFACENGCOM Headquarters.
Survey Requirements. For all replacement track design, where the
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existing foundation is to be reused, the following survey tolerances are
required.
a) Transit and Distance Measurement Tolerance. Transit and
distance measurement survey to locate the centerline of the existing track
should be made to the closest .005 foot for distances and 20 seconds for
angles. The centerline of rail for a four-rail system shall be the centerline
of standard gage, while the centerline of rail for the two-rail system shall
be the centerline of each rail. If it is the intent to utilize the TRACKS
program, the survey data should include for inner and outer rail: delta
angle, deflection angles to, and chord lengths between points about 5 feet
apart along the existing track. Control points should be made permanent to
last at least 2 years.
b) Dig-Up Survey Measurement Tolerance. Dig-up survey, to locate
the centerline of the existing track in relation to the centerline of the
existing foundations, should be made at locations spaced at 15-to 25-foot
intervals along the curve. The actual number of dig-up locations is
determined by the type of curve and by the matching relationship of the rail
and foundation centerlines.
Foundation Structural Analysis Requirements. A structural analysis
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shall be made of the track foundation, for eccentricity, by the responsible
structural authority. This analysis shall produce maximum allowable distances
that the track centerline may be offset from the foundation centerline. These
allowable eccentricities shall not be exceeded by the replacement track design
without express approval of the cognizant NAVFACENGCOM Engineering Field
Division.
Replacement Track Design Requirements. A replacement alignment
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design shall be made of inner and outer rails in accordance with the pertinent
criteria of this chapter and, if the TRACKS computer program is used, with the
Application Manual for Portal Crane Track Design and the TRACKS Users Manual.
This design shall include proper mathematical steps and adequate checks to
insure that the following criteria are satisfied:
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