SDC Torsion Design

office (847) 816-3816
fax (847) 816-3971
toll-free (888) 425-2475

Welcome to SDC

SDC is an engineering firm that excels in the inspection, upgrade, alignment, and rehabilitation of EOT Cranes and Crane Runways.  The principals of SDC have over 100 years of industry experience in solving crane and crane runway maintenance problems.

Do you have any of the following problems?

  • Worn Crane Wheels or Rails
  • Torn Girder Tie-Backs
  • Sheared Thrust Plate or Bracing Bolts
  • Cracked Crane Girder Welds
  • Crane or Trolley Drift
  • Cracked End Trucks
  • Overloaded Crane Runways

Check out our website and see if we can help you!  It is full of information that you will not find elsewhere. 

Our goal is to help you sort out and solve your difficult crane/runway problems.  We are still under construction and plan to continually upgrade our site to help both Plant Engineering and Crane Maintenance understand the interaction between EOT Cranes and Crane Runways. 

Please contact us if you would like to discuss a particular problem.

CRANE GIRDER PRO is Now Available 

In 2005, the 13th edition of the AISC Code was published. The new AISC Code contains significant updates that affect the design of crane girders including the fatigue analysis. Specifically, the new code has additional requirements for the consideration of lateral-torsional buckling in the design of members for flexure. For standard structural sections, this new requirement is not a difficult task. However, for crane girders constructed from built-up sections, this task is extremely challenging. The design engineer needs to determine the shear flow in the girder that conforms to zero warping shear stress at the terminal ends of the girder cross section. The design engineer then needs to calculate the torsional warping constant (Cw) with respect to the principal axis of the section to solve the code equations.

The new code provides minimum guidance regarding the lateral-torsional buckling stress of unsymmetrical shapes. Professor Ted Galambos has provided SDC with guidance regarding the combination of stresses and determining the lateral-torsional buckling stress noted in Section F12 of the AISC Code. 

SDC has revised its crane girder design program to meet the requirements of the 13th edition of the AISC Code. Our crane girder design program is written in Microsoft Access to perform the difficult task of performing a full torsional and fatigue analysis of the crane girders that meets the new code criteria.

Attached are the results of our crane girder analysis used to upgrade the load capacity of a crane runway from 110T to 120T.

SDC Torsion Design/W40x324+THPModel Plot.pdf

The girder was subdivided into 3 zones. The girder stresses were calculated for each zone since the maximum fiber stresses are not located in the area of the maximum torsional and shear stresses. Enveloping the maximum stresses using a single zone leads to a conservatively designed girder for a new crane runway. However, this simplified process does not aid in the requalification of an existing crane girder for heavier loading.

The most cost effective means to upgrade the crane runway load capacity or crane runway load rating is to add additional steel to the bottom flange of the girder.  By changing the cross section of the girder in Zone 2, SDC can design a "step girder".  The step girder design will not change the crane girder cross section at the column connection making it a cost effective solution.  The additional steel is added to the girder between the columns with a "step up" at the ends.  The resulting crane girder cross section will be variable.   SDC has developed a new methodology to perform a full torsional analysis on a variable section crane girder that will also meet AISC Section F12 requirements.

WAARP is Now Available 

SDC announces a our new WARPP computer program geared for calculating the both the flexural and torsion-related section properties of any arbitrarily shaped open section for structural members having either a constant or variable profile geometry. WARPP calculates the following mechanical properties to facilitate steel design per the AISC Manual of Steel Construction 13th Edition:

  • Elastic Centroid Location (Cx, Cy)
  • Plastic Centroid Location (ex, ey)
  • Plastic Modulus (Zx, Zy)
  • Principal-axis Moments of Inertia (Ixp, Iyp)
  • Pure Torsion Constants (J)
  • Shear Center location
  • Warping Constant (Cw)
  • Torsion characteristic parameter (β)
  • Statical Moments (Qx, Qy)
  • Warping Static Moment (Sw)

Attached is a sample output for an arbitrary open shape Detailed Open Section Properties.pdf We chose this unusual shape to help validate a number of logical and numerical procedures/subroutines that:

  1. automate the shear flow scheme
  2. calculate the shear center-based properties of the section, for which the shear flow pattern is not obvious.

The shear flow application is correct only when the resulting warping static moment (Sw) vanishes at the end of all branch terminals. Otherwise the warping constant (Cw) would definitely be in error due to a flawed shear flow pattern.

SDC will provide services to calculate the shear center along with the torsional warping constant for structural engineers designing complex girders or manufacturers of cold formed steel products.