Load monitoring: 'It's only supposed to weigh a tonne!'
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Transcript of Load monitoring: 'It's only supposed to weigh a tonne!'
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Load monitoring: 'It's only supposed to weigh a
tonne!'
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Who We Are:
• More than 3 decades of experience in load monitoring and rigging, including accident investigation.
• Involvement in international load monitoring & rigging projects (including projects with NASA and Boeing).
• Design and manufacture of load monitoring and overload prevention systems.
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Look at this picture. Do the lines seem parallel?
Well, check with a ruler- because they are!
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Which of the yellow lines is longer?
They're both the same length!
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Does this load seem to be equally distributed?
It’s not, although the truss is completely horizontal!
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What about this truss?
Hard to believe, but the load is distributed completely equally!
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There is absolutely no connection between a truss being horizontal and equal load distribution!
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The reason behind this visual deception is the phenomenon in physics known as:
Statically Indeterminate Structures:
Each time there are more than two supports on a truss or more than three supports on a structure, the state of Statically Indeterminate Structure occurs, which results in an unpredictable load distribution.
Consequently, some of the motors may become dangerously overloaded -- while other motors may bear only a small part of the load.
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This phenomenon is very tricky:
• It misleads us into concluding that a horizontal truss means that the load is equally distributed.
• It might happen even if we know the weight of each item and the total weight of the structure .
• It has absolutely nothing to do with experience.
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Day to day reality is complicated due to this phenomenon:
• Production loads are becoming heavier and more dynamic.
• Multiple motor lifts are commonplace.
• Regardless of how experienced we are, and even if we know the load, load distribution is unpredictable.
• Tons of equipment are hung above performers and the audience.
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Tons of equipment hung above a large group of performers …
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Tons of equipment hung above a very crowded audience …
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How many unnecessary accidents happened, causing many millions of $ in damages and more importantly injuries and casualties?
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The influence of statically indeterminate structures on everyday rigging activities:
How many times has a situation been potentially close to failure and nobody knew?
How many times has a little bit of good luck averted an accident?
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There is no practical way to know real load distribution unless loads are monitored.
We must monitor loads and make sure they are distributed as intended.
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Principles of load monitoring:
Loads should be monitored continuously
• because load distribution easily changes (for example, every time the rigger touches the controller).
• from installation to de-rig, not only at the first show.
Immediate warning of the shifting load
• when overload starts to develop the system notifies the rigger with the exact location of the overload, enabling prompt preventive action.
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The benefits of load monitoring:
• Continuous protection against overload, preventing injury and costly accidents.
• Saves resources customarily used to increase the safety factor when loads are unmonitored.
• Enables the use of venues previously ruled out because of doubts over load bearing capacity.
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To conclude, there are two options:
The first is to do nothing, ignoring the danger and hoping for the best…
Or:
We can face up to the challenge and to our responsibility. How? By monitoring all loads rigged above people, ensuring their safety.
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There is a growing number of productions & venues that continuously monitor their loads .
Here are some examples:
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Sydney Opera
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Esplanande Opera on the bay - Singapore
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Munich Olympia Park
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Boston Symphony Orchestra
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Casa da Musica - Porto
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Orange County Convention Center - Orlando
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AC/DC Black AC/DC Black Ice World Tour
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Human Castle Barcelona
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and thanks to the German company, Dart , the European shows of Metallica…
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Elton John…
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Cirque du Soleil…
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Lionel Richie, and many others.