SDC has been inspecting crane girder runways since 1988. Some runways could have several hundred structural deficiencies if the low priority items are included.
Structural repairs are normally made to the very high priority items only. The highest priority items are crane girder weld and base metal cracks.
Crane girder failures almost never lead to total collapse. However, some of these cracks could lead to collapse if not immediately repaired. SDC finds severely deficient crane girders on a regular basis in all steel mills.
At AISC’s request, SDC performed an analysis of Example girder 14.1.3 as shown in AISC Design Guide 7.
The purpose of this analysis was to compare the results given in the example problem with the results generated by SDC’s CRANE GIRDER PRO computer program.
CRANE GIRDER PRO performs a full blown flexure-plus-torsion stress analysis followed by a complete evaluation of structural strength against material yielding and metal fatigue. The girder analysis is accomplished without the use of Flexure Analogy to perform the torsion analysis.
Notably CRANE GIRDER PRO is capable of treating flexural and torsional responses to any load vector pointing along any orientation, regardless if it passes through the shear center. Load responses were enveloped from a classic moving load analysis that can track behaviors owing to multiple wheels marching on any intervals along the girder span as crane bridges down the runway.
Derived from user supplied section geometry (whether symmetrical or unsymmetrical, uniform sectioned or variable sectioned) CRANE GIRDER PRO establishes a definitive path of shear flow, locates the elastic centroid, plastic centroid and shear center through numerical integration. It then completes the section properties that includes cross sectional area, flexure static moment, flexure moment of inertia, warping constant (Cw), unit warping and warping static moment etc. CRANE GIRDER PRO provides two sets of section properties. One for the fully effective section and the other for post-buckled section.
Once the static section properties and the dynamic structure responses to loads were complete, CRANE GIRDER PRO calculates various categories of flexural and torsional stresses at every nodal incidence for every element. The domains of stress were mined further at each node seeking the peaks and valleys of values associated with tensile stress fluctuation and shear stress reversal conditions to perform the required fatigue strength assessment.
Click on the links below to view or download the forensic analysis of a crane girder similar to the AISC Design Guide 7 example girder 14.1.3 that has catastrophically failed.
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