Chapter 6 – Crane Rail Alignment and Load Specification
Table of Contents
6.1 Is There Anything beyond Primary and Ordinary6.2 Defining Rail Offset (Rail Float, Rail Misalignment, etc.)
6.3 Torsional Effect Once More
6.4 Nonlinear Effect from Rail Offset – A Warm-up
6.5 Rail Offset Reality Factor – The Definition
6.6 Rail Offset Reality Factor – The Reality
6.7 Rail Offset Reality Factor – The Implication
6.8 Runway Structural Design Information Process – Planning
6.9 Runway Support Loading Input – Specifying
6.10 Rail Offset – The Referential Issue
6.11 Rail Offset – The Uncertainty
6.12 Rail Offset – Design Consideration
6.13 Runway Design Rail Float (Rail Misalignment) Specification
6.14 Applied Torsional Moment Mz (Mt)
John Fong (馮永康) . Bill Vanni
Structural Design Corporation
1133 Claridge Dr., Libertyville, IL 60048
©July 2018 – 2019, 2022, 2025
By choice, many of us set higher priority tending to problems that we “think” are more preeminent or more important, or to certain issues we feel more comfortable to deal with, etc. than paying needed attention to (1) salient topics “misidentified” as less significant or (2) those serious matters being “mistaken” as unimportant.
Some of us often rely on Basic Structural Engineering Instincts getting by with barely good-enough proficiency to resolve difficult issues, “thinking” it should not lead to any negative side effects.
One of the approaches or practices making pseudo logical sense that often plays into our favoritism is;
To pick and choose for professional and/or personal convenience doing what “seemed” totally fair and reasonable, like engaging exclusively with those well-understood primary-ordinary structural behaviors, which mainly were the results linking to well-recognized primary-ordinary loadings and effects
Sort of infallibly taking it easy there and enjoying an easier time. And so it goes by and large, it fosters a well-accepted engineering way of life by default
Barring no question asked, so long as our eye sight is focusing at nothing else but those easily-comprehended structural behaviors, then a blurry mix of wrong-could-be-right against right-could-be-wrong styled norm can take charge, ended up affecting everything we do
On the downside,
Some of our more modest behaviors such as avoiding difficult situations or carelessly making false engineering judgment, etc. can cause undesirable consequences. But, should any disarray emerges as a result, if not restored promptly enough and in the event coupled with untimely mischance, could lead to catastrophic failures
The worst part is many of us caught up in it but don’t know what had struck
One of the most formidable rationales ‒ took hold for far too long already ‒ was rooted from an unconditional “fancy” in that every variation of structural behavior and response to loads, regardless to the unique nature of each, would fall consistently into the sanctuary of simple bending, even when the implication is absolutely untrue on special occasions.
Once the firmly established habit of (1) dealing exclusively with well-understood structural behaviors and well-popularized stress categories and (2) observing design mandates based solely on “simple bending supposition” has dominated the academia and mainstream design practice then, it should be of no bigger surprise why qualifying structures against the well-recognized loadings and effects singularly has become such an important share of our primary engineering objective, or in many cases the only objective.
On the surface, it seemed nothing seriously wrong when pinning an undivided emphasis on well-recognized primary-ordinary loadings-effects and those well-comprehended primary-ordinary structural behaviors, because to certain structures serving certain functions, it usually works out perfectly with no major side effect, but, hopefully it never does
Clearly that, such an overpitched favoritism and unwavering blind trust into simple bending or overplayed design tradition could congeal unawareness − if not ignorance − of the existence of certain ostensible secondary effects being falsely categorized as subordinate-counterpart of those primary-ordinary loadings-effects
In essence, those secondary effects, unless demonstrated by calculation or blessed by solid R&D, should not be pre-recognized as less important or as secondary by nature without solid proof
Whether to agree or disagree with the foregoing notion isn’t a compelling issue here; but all in all, talk is cheap. Trouble or no trouble came out of any event, primary or secondary, must have solid numbers as backup. The concern as to what level of detail is needed to make the point across would depend on what type of structural function is anticipated to provide for what type of industry serving under what type of on-site environment, etc.
The reality is; many secondary occurrences, like many not so well-recognized (or well-respected) effects can subsist well below our radar screen doing their magic, often quietly and seemingly harmless, especially when no one looks closely.
Nonetheless, for certain type of structure serving certain type of industry experiencing certain chronic distress, it is extremely important to verify should a certain “secondary” incidents be suspicious of any threat or not; otherwise we may never come to recognize the seriousness of their potential destruction imparted on our structures, if it does in particular to structural members having unusual geometric configuration exhibiting extraordinary behaviors when subjected to loadings and effects of extraordinary nature then, what should we do?