Presentation on theme: "Load monitoring: 'It's only supposed to weigh a tonne!'"— Presentation transcript:
Load monitoring: 'It's only supposed to weigh a tonne!'
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.
Look at this picture. Do the lines seem parallel? Well, check with a ruler- because they are!
Which of the yellow lines is longer? They're both the same length!
Does this load seem to be equally distributed? It’s not, although the truss is completely horizontal!
What about this truss? Hard to believe, but the load is distributed completely equally!
There is absolutely no connection between a truss being horizontal and equal load distribution!
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.
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.
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.
Tons of equipment hung above a large group of performers …
Tons of equipment hung above a very crowded audience …
How many unnecessary accidents happened, causing many millions of $ in damages and more importantly injuries and casualties?
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?
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.
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.
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.
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.
There is a growing number of productions & venues that continuously monitor their loads. Here are some examples: