SDC Torsion Design

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Crane Rail Alignment Survey

SDC has successfully performed crane rail alignment surveys in steel mill buildings for over 20 years.  Our survey procedure is briefly described below:

Field Measurements

  • EOT Crane Survey
    SDC performs surveys to determine the end truck alignment, wheel alignment, and wheel gauge. A 90 degree angle can turned to determine if the crane is square.  The crane surveys will be referenced off the base lines used to perform the crane rail survey.
  • Crane Rail/Girder Survey
    SDC will establish survey baselines that will be used to measure the offsets to the crane rails, crane girders, and column flanges. SDC will take the measurements off the baseline at the ends and center of each crane girder. Crane rail measurements will be taken off the baseline to the crane rail at each building column location. The relative elevations of the crane girders will be shot at each building column.

CMMA Requirements

  • Crane Span
    The nominal crane span can vary (+/-) 3/16" for a 50 foot long crane.  The variance is increased to (+/-) 1/4" for a 50-100 foot long crane and (+/-) 3/8" for a crane longer than 100 feet.
  • Crane Rail Straightness
    The nominal crane rail span can vary (+/-) 3/8" with a maximum rate of change of 1/4" in 20'-0".
  • Crane Rail Elevation
    The nominal crane rail elevation can vary (+/-) 3/8" with a maximum rate of change of 1/4" in 20'-0" along a column line.
  • Rail-To-Rail Elevation
    The nominal crane rail elevation across the bay can vary (+/-) 3/16" with a maximum rate of change of 1/4" in 20'-0" along a column line for a 50 foot long crane. The variance is increased to (+/-) 1/4" for a 50-100 foot long crane and (+/-) 3/8" for a crane longer than 100 feet.

Crane Rail Alignment Drawings

SDC will generate Autocad drawings showing the results of the crane/rail survey along with a recommended crane rail realignment or girder shimming as required.  It is our experience that it is nearly impossible to maintain the CMMS Requirements due to various, permanent building movements.

SDC will recommend a best fit alignment with the crane girder centerline.  There are currently no guidelines to help Engineering or Maintenance Departments deal with over/under gauge of the crane girders.  SDC performs a full crane girder torsional analysis (including warping normal and shear stresses) to determine the girder stress state when the rails must be offset from the girder centerlines. 

Wheel/Rail Interference Study

SDC can use the crane and crane runway survey data to perform an interference study between the crane wheels and over/under gauged crane rails.  This study is used to determine if crane rails need to be relocated off the crane girder centerlines.

Crane Rail Shims

SDC does not recommend use of shims to level a crane rail.  We normally shim the column base plate or column cap plate.  We may recommend a small shim to eliminate a knife edge where two crane girders meet at a cap plate.  Any knife edge could cause the crane rail to break.