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The Power of the Beam

By | Cantilever Beam, Resources | No Comments

The Amazing Inside Story of how a Cantilever Beam Works!

Cantilever beams, also known as outrigger beams, are frequently used to support the end of a rope from which a suspended scaffold hangs.  Have you ever wondered how that beam works, especially if you are on the other end of the rope?  Well, here’s the story.

A cantilevered beam is one component of an assembly that consists of a number of parts and pieces that provide the necessary support for the loads that are hanging on the rope.  The beam is designed to use the advantage of leverage; this reduces the amount of force on the rear end of the beam (that would be the other end from where the rope is connected).  Of course, the beam cannot do the work alone.  It must have support towards the front end and the rear end.  The support at the front is called the fulcrum or front support (that’s clever engineering jargon).  The cantilever of the beam is measured from this front support to the point of rope attachment.  This is a critical dimension since the beam has to be strong enough to transfer the load from the rope back across the fulcrum and then to the rear end.  At the rear end is the other support.  Yep, you guessed it, it’s the rear support, also known as the “inboard end”.  This is where the counterweight is located or where the beam is connected directly to the supporting structure.  Now, in order for the whole system to work, the counterweight has to be big enough, if used, or if the beam is attached directly to the structure holding everything, then the connection has to be strong enough and the structure has to be strong enough.  So, how strong does it have to be, you may ask?  Well, strong enough.

Actually, this is where it gets interesting.  The fulcrum load can get rather large, depending on how much the beam sticks out.  And the counterweight can get pretty big too, particularly since you need four times what is actually required to keep the beam from going over the edge of the building.  Incidentally, don’t tell the erection crew that they are carrying 4 times the required counterweight up the stairs; you’ll have a mutiny on your hands.  Other than make the erection crew work harder, there is a very good reason for the extra counterweight.  In engineering terms it is called the safety factor.  In laymen’s terms, the extra counterweight is for typical jobsite screw-ups, such as overloading the suspended scaffold.

Where can the system go wrong?  Unfortunately, there are several places where the unqualified designer can make a fatal error.  First is in the supporting structure.  If the cantilever beam is installed on the roof, the roof has to hold the load.  I’m always surprised how casual some people can be about the strength of a roof, particularly on an older building or one where the maintenance is lax and structural damage has occurred.  While a structural analysis of the roof is typically not within the scope of the typical scaffold installation, it is also typical that the individual charged with the investigation of the roof’s strength will need an accurate submittal of load information as a result of the scaffold loads on the cantilever beam.

The second opportunity for a fatal error is with the beam itself.  The beam has limits.  Just because the beam is 16 feet long doesn’t mean you can cantilever it 8 feet, or for that matter 15 feet.  Funny things start to happen as a beam is cantilevered; the beam likes to wander sideways out there at the front end where the rope is connected.  While most people expect the beam to deflect, that is, start to droop (another one of those engineering terms) few people expect it to wander.  Unfortunately, like an unsupervised teenager, if it wanders too much it gets into big trouble.  Depending on the shape of the beam, too much sideways wandering can make the beam roll, deflect vertically and fail.  If the scaffold users are lucky, the beam will just fold over and the scaffold occupants will wind up on the evening news.  If unlucky, the beam will break and the scaffold will collapse and fall to the street below.  The good news in this scenario is that assuming the scaffold users are utilizing personal fall arrest equipment, like they are supposed to, they’ll be saved from the fall but will still wind up on the evening news.  Hopefully nobody on the street below will get hit by falling debris.

The third possible fatal error is losing the rear end support.  If counterweights are used, they must be mechanically connected to the beam; that is, the counterweights cannot be precariously stacked on top of the beam or haphazardly wired to the beam.  In fact, the counterweights must be specifically designed for the beam and the connections.  If the beam is directly connected to the supporting structure, not only does the connection hardware have to be strong enough but the roof structure components must be able to support the load.  In many cases this will require the services of a qualified Professional Engineer.

The fourth fatal error involves the lack of knowledge of the designer, erector and/or user.  If any of these participants does not have the training and expertise to correctly complete his or her obligations to the project, disaster can occur.  Qualified design is essential; correct installation, according to the design, is imperative; pre-workshift inspections of the rigging are crucial, and; correct scaffold usage, by trained workers, is critical to the safety of the project.

The fifth fatal error, which follows from the fourth fatal error, is lack of training.  All the equipment in the world won’t save you from an early demise if you do not know how to use it.  Training is the key!  And, where can you get that training?  Go to www.scaffold.org for starters.

How’s the Outlook

By | Resources, Scaffolding | No Comments

Since I was asked to offer my outlook for 2006, I can only assume I did an incredible job of predicting 2005!  That’s right, back in January 2005 I offered my opinion of “what does 2005 hold for the scaffold industry?” This year I have been asked to do the same for 2006.  So, the only conclusion that I can think of is that all my predictions came true last year.  Let’s check it out and see how I did:

 

I predicted that over one hundred fatalities would occur involving scaffolds.  I was really hoping I’d be wrong on this but it appears that we didn’t improve on this record much in 2005.

 

I predicted that training would not live up to expectations.  Based on my personal experience, and from what I’m told by others, this prediction continues to remain true.  While the industry continues to provide training, it’s amazing how much more we have to do.  Perhaps some of it has to do with the turnover rate in the construction industry.  Perhaps it has something to do with the language barriers so prevalent on many construction sites.  Whatever the cause, 2006 will continue to provide huge opportunities to improve the knowledge and expertise of the construction worker, especially as it relates to scaffolding.  What can you do to help?

 

In January 2005 I complained that individuals would continue to “refuse to accept responsibility for their actions.”  I don’t know, has this changed?

 

In January 2005 I thought life would be good in the scaffold business.  From what I read and hear, looks like I was right on this one—can’t say I can take responsibility for this growth though.  Everybody seems to be busy; why not continue this level of activity for another year. I predict that 2006 will be another good year.

 

I expressed the opinion that the federal government would not increase funding for OSHA.  I was right about this.  In fact, for 2006, I think we will continue to see a lack of commitment by the federal government to support OSHA, the OSHA Training Institute, and the various programs that are essential if we expect to see any improvement in the safety and welfare of the worker.

 

In January 2005 I predicted that certain irresponsible scaffold suppliers would continue to use workers that are not fully trained.  Can it be possible that in 2006 this can change?  I don’t think it will, by why not surprise me?

 

The fact is, back in January 2005 the outlook I saw, and the predictions I made were predictable.  None of this should surprise you if you are at all familiar with the scaffold industry. Construction work is unique.  For example, scaffold erection and dismantling work is tough.  It demands physical agility, stamina and manual dexterity.  It exposes workers to hazards that the average employee would never accept.  Scaffold users face similar situations.  Imagine if the typical office worker had to climb a ladder 30 feet or more in height to get to his or her desk.  Imagine if that desk was in an office where the temperature varied anywhere from below zero to above a hundred degrees (Fahrenheit that is). Finally, imagine that you received little or no training in the work you were expected to do.  Oh yeah, every week the office furniture gets moved around so nothing is the same!  And people think that construction work is a no brainer.

 

We struggle to find qualified workers that will work for the wages offered.   We expect these workers to follow instructions in spite of the fact that we cannot communicate in the same language.  We blame the inefficiencies on the worker, the schedule, the system, or the project.  Unfortunately we don’t seem to be focusing on the factors that can change the industry.

 

Yes, 2006 can be a good year.  In spite of the needless obstacles we find in the industry, I think that we will continue to improve the safety and the welfare of the scaffold erector and user.  Will this progress be reflected in a decrease in injuries and fatalities?  It will take all of us to make 2006 the year it should be. You need to be part of it.