When you question the safety, he assures you the rope will be strong enough. “What could possibly go wrong?” he says.
As ridiculous as it sounds, this adventure experience is installed on buildings every day. It’s just that it isn’t called an adventure experience—it’s called a suspended scaffold.
Think about it: a suspended scaffold is nothing more than a platform hanging from a rope or ropes secured to something on the roof.
For those in the industry who do this every day, hanging from a rope is no big deal. And it isn’t a big deal until something goes wrong. It then becomes a big deal very quickly, particularly if you are the one hanging from the rope.
Understanding the load path
What could possibly go wrong? Nothing, if everything is working correctly and all the components are functioning as expected. Interestingly, one of the big causes of a suspended scaffold collapse is the failure of scaffold erectors and users to consider the route the load takes as it is transferred from the platform to the structure upon which the scaffold is installed. The route that the load takes from the platform to the structure is called the load path.
The load path may start with a worker who, while standing on a suspended scaffold platform, applies a load to the platform. To transfer the load to the structure, each component in the path—including the stirrups, bolts, pins, hoists, suspension ropes, shackles, beams, and counterweights—must have the strength to not only support the load, but also the ability to transfer the load as it travels from one component to the next component in the path. If any of the components fail to support and transfer the load, it will fail, and the scaffold will fail.
When a single component fails
A single component failure may or may not be catastrophic, depending on the criticality of the component. For example, loss of electrical power for the hoist would be significant but not catastrophic. However, a suspension rope that breaks would be catastrophic.
While safety factors and additional safeguards, such as personal fall arrest systems, are used to alleviate the possibility of catastrophic failure, these measures do not compensate for human error in the erection and use of suspended scaffolds.
The splice: a critical connection
As an example, take the splice that is used to join two members of a cantilever beam to each other. The splice is designed to make the beam act as one beam despite it being in two or more pieces.
As the load moves from the tip of the beam towards the back of the beam, it travels through the splice. For a splice to work, it must not only move the load, but it also must
Resist the bending that is caused by the cantilever of the beam. Consequently, bolts or pins are used to assist the movement of the load. If an errant erector leaves out a few bolts, the splice cannot function as expected, and the load path may take a detour.
That detour, with the help of gravity, will send the load on a different route, resulting in an undesirable outcome which culminates in an early demise for the scaffold user. That is not a desirable outcome, to be sure.
The danger of overloading
Overloading the platform is another example of how the load path can deviate from the desired route. While manufacturers are very explicit as to the limitations on their equipment, scaffold users constantly tickle the fickle fingers of fate.
Placing an excessive load on a platform will detrimentally deflect the platform. While the user assumes that since it isn’t broken, it must be OK, it isn’t. The deflection introduces forces for which the scaffold was not designed, thus altering the route the load takes on its journey to the structure, producing objectionable results.
The designer’s highway
The lesson here is that the scaffold designers have determined the path by which the load is to travel. Either follow the intended route or reroute the load at your own risk.
The designed path is the superhighway to success. On the other hand, the path you build may have potholes, or it may end at a cliff. Which will you choose?
