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Monthly Archives

February 2013

Scaffold Legs Under Duress

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An Introduction to Panel Points and Why They are Important

After reviewing many user manuals for scaffold, it is clear that scaffold manufacturers understand the strong and weak locations of each of their respective systems.  However, I have not seen any scaffold user or technical manual attempt to explain to their users why they always show scaffold tie placements at the intersection of horizontal and vertical diagonal members (typical for system scaffold).  In this brief article, I’ll attempt to demonstrate some reasoning behind tie location placement.  We will be introducing the concept of “panel points” and their importance in scaffold construction.

The typical definition of a panel point is “the point of intersection where a web (or webs) meets a chord”.

Okay, that probably doesn’t help you much.  See Figures 1 & 2 for a better graphical representation of what we’re talking about here (note the deflected shape of the scaffold for effect).  As the above definition is generally used for structural trusses, a better way to define panel points for scaffolding would be as follows: “the intersection where horizontal bearers, runners, or vertical diagonals meet a vertical leg”.

Now that you know what a panel point is, let’s dig into why it is important.  The magic (physics) of a panel point is straightforward.  If a load is applied directly to the panel point, the supporting members are loaded primarily in tension or compression with little or no member bending forces.  Members have larger capacities when they are only required to transfer tension/compression forces compared to bending and tension/compression forces.

As a simple illustrative example, pretend you are a scaffold leg.  Now pretend you need to hold Dave Glabe’s prized “D. Victor Saleeby Bronze Eagle Award” over your head, say 150 lbs (Dave feeds his award three solid meals a day and it has reached an impressive girth).  In this instance, you would be a compressive member transferring weight of the bronze Eagle through your body and into the ground.  If you wanted to mimic a combination compression and bending member, have someone tie a rope around your waist and pull on you.  Not so easy to hold that 150 lbs. eagle over your head now, is it?  With this image in your head, you are now one with the scaffold leg and a step closer to scaffold enlightenment!

So remember, panel points keep scaffold members in tension/compression, not bending plus tension/compression.  Therefore, slapping a significant load bearing tie in the middle of a 10 foot scaffold tube would probably not be the best idea!  Attaching or directing a load to a panel point is better than attaching or directing a load at any other spot.  Of course, we are talking aboutscaffold in general terms and there are always exceptions.  Don’t think this article gives you the knowledge to do anything in violation of the OSHA standards or the manufacturer’s recommendations.  When in doubt, always consult with a Qualified Person.

 

dlm-figure-1

 

dlm-figure-2

Tricks of the Shoring Trade

By | Resources, Shoring | No Comments

How to Ensure Safety While Shoring an Existing Structure

Shoring existing structures can be a tricky business.  Typically, the older the building is the more complicated the shoring of it can become.  Many older structures do not have drawings of the existing construction and if they do, they are not always reliable.  Many buildings go through generations of remodel with additions, renovations and improvisations that are not always documented or constructed properly.  Without proper documentation, it is sometimes tough to determine the load bearing members in an existing building which makes it challenging to shore it properly.  Difficult access to these documents does not give you a free pass on when and where to shore.  If you can’t figure out where the loads are concentrated, you can’t figure out how to safely support anything.

When undertaking the task of shoring an existing structure, you should consider consulting a Professional Engineer – and I don’t just say that because I happen to be one!  The peace of mind that you get from entrusting this work to an engineer far outweighs the risk of liability if something were to go wrong during the shoring operation.  An experienced professional can help you determine not only how to safely shore the structure, but how to do it in the most economical way possible.

Pertinent information that you will need to know before starting a shoring plan includes but is not limited to: the type of work being performed, the boundaries of work, distance to any excavation, dimensions of the building and location of load bearing members.  Other relevant information includes the dead load of the supported area and any anticipated live loads.  Examples of live loading conditions that need to be evaluated include determining whether the office building or parking garage will remain operational during construction.  You also need to consider if there are any special circumstances such as required access openings in the shoring plan or work sequencing that would affect the standing shores.  Do snow and wind loads need to be taken into account?  Be certain to consider all of these circumstances when developing the conceptual shoring design.  Drawings, schematics and photographs can be provided to convey most of this information.  However, in some cases it is easier and more cost-effective for the engineer designing the shoring plan to visit the site.

If you do not follow the correct protocol and improperly shore an existing structure, there is increased likelihood of damaging the building or of a complete collapse during construction.  Choosing to retain the services of a Professional Engineer and providing them with as much accurate information as possible will help minimize risks and ensure the most accurate and economical design possible.  Don’t take chances; if in doubt regarding the stability of a structure, always err on the side of safety.  Get a Professional Engineer involved and maximize your chances of shoring success!

Trust the Math for Your Eyes May be Deceived

By | Fall Protection, Resources | No Comments

 An inside look at why fall protection anchors must be tested

Fall protection!  When you put on your harness, tie off to a fall protection system, and step to the edge of the roof on a 20 foot tall building, do you know that you are truly safe?  Or is this maybe just a false sense of security that you have been lulled into?  Would you feel different if this were a 200 foot tall building?

As we all know, the components of a complete fall protection system are the user’s personal fall protection equipment and a suitable anchor or lifeline to connect it to.  If the system is properly designed, constructed and used, it will ensure that you will walk off the jobsite at the end of the day safe and sound.  As a user, you can only control the “use” aspect of the system so a great deal of responsibility is on you to ensure your own safety.  If you are a gambler, you can take your safety on faith.  However, those who do not want to rely on dumb luck need to know their fall protection system.

First, the simple stuff: your body harness and lanyard.  They should be purchased from a reputable source with readily available design and testing data from the manufacturer.  Utilizing your Fall Protection User Training, you should be able to perform a visual inspection of the equipment to check for damage or excessive wear.  If all looks good, you should feel comfortable that your personal fall protection equipment will do its job.

On the other hand we have the anchor portion of the system – this is not so easy.  You can look for visible signs of damage or corrosion, but the truth of the matter is that in most cases you have no idea what is behind or underneath the anchor itself.  It is in these areas where corrosion hides and maintenance tends to neglect.  The truth of the matter is that if the anchor was not designed and installed properly, no amount of maintenance can make it safe to use!  You may be thinking the anchor is fine and dandy because that steel beam over there is “big”, or that wall looks “solid” . . . there is no way that it won’t hold 5,000 pounds!  This may be true, but as you stand there looking at the “big” steel beam ask yourself this: what is holding the beam in place?  Okay there is a steel column at both ends, but what are they attached to?  If you don’t know, how can you really be sure that “big” steel beam isn’t going to follow you over the edge of the roof if you fall?

OSHA requires that all permanent fall protection anchors must be tested upon installation and be visually observed annually if they are to remain active.  The fact of the matter is that many property owners simply do not know about these requirements as many building anchors are used daily which have never been tested or inspected.  This puts you at risk of injury, and the property owner and your employer at risk of a hefty lawsuit if something were to go wrong.

We were recently involved in a project which involved the load testing of existing fall protection anchors around the perimeter of the mechanical penthouse.  The anchors were installed on the outside face of the brick veneer and consisted of a steel eye welded to the center of an 18”x6”x 1/8” thick steel plate.  The plate was bolted to the wall with two ½” diameter threaded rods and nuts at both ends.  On this particular structure, we could observe that the other end of the connection inside of the penthouse was identical to the connection on the outside.

Existing anchors outside of mechanical penthouse.

Existing anchors outside of mechanical penthouse.

 

Existing anchors inside of mechanical penthouse

Existing anchors inside of mechanical penthouse.

 

From the pictures above, you may be thinking it looks like someone clearly put some thought and effort into installing these anchors so they must have been designed and installed properly.  No rust is apparent and the wall appears “solid” . . . why do they need to be tested???  The reason we were asked to test the anchors is because someone didn’t feel like gambling as they prepared to hang off the side of the building and asked the correct question “can I get a copy of the latest testing and inspection reports?”  As it turns out there was no record that the anchors had ever been tested or inspected, and more disturbing that they may have never been designed either.  Fortunately in this case, the property owner and contractor were well aware of the OSHA requirements and requested the anchors be tested before use.

Armed only with a single architectural section of the penthouse wall, we felt it would be prudent to perform a structural investigation prior to performing any testing.  During this investigation we discovered that the two threaded rods were installed adjacent to the light gauge steel studs at most locations.  Running a computer modeled analysis of this configuration yielded results which confirmed that not only were the anchors not suitable for their intended use, but that testing them could potentially damage the building!

Since the existing anchors were determined to be inadequate, new anchors were designed and installed and the old anchors removed and/or taken out of service.  During the testing of the new anchors, we were asked to test one of the existing anchors in a location that a new anchor could not be installed due to equipment conflicts inside the building.  The test was halted at only 1400 pounds as the outside plate had already deflected ½ inch with this minimal load applied to it!

 

Picture during testing of existing anchor

Picture during testing of existing anchor.

 

The topic of fall protection anchors is cussed and discussed all the time, but we still have individuals who are either uninformed regarding the OSHA standards or they simply don’t care.  The anchor may look “big”, and that wall may appear “solid”, but the only way to know with certainty that it is safe is through proper testing and annual observation.  As a user, you need to be cognizant of your own safety and simply ask for the latest fall protection anchor testing or inspection report before you go trusting your life to it.  This will provide you with peace of mind, and you may educate someone else about the OSHA standards in the process which may save another life down the road.

General Industry or Construction?

By | Resources, Scaffolding, Uncategorized | No Comments

Should the scaffold you just erected in the local oil refinery comply with the US federal Occupational Safety & Health Administration (OSHA) General Industry Standards or the Construction Industry Standards?  While you might think this is a question with an easy and simple answer, it isn’t.  Does it matter which standards apply?  That question has two answers: from a compliance standpoint, yes.  From a safety standpoint, not so much.

Erecting a scaffold in an existing oil refinery would suggest that the General Industry standards would apply since the refinery is completed and not being constructed.  This would be an incorrect conclusion: Determining which set of standards apply to a specific situation is much more complex.  While OSHA has a definition for “construction,” there is no definitive regulatory description of “maintenance” or “general industry” where it would be clear to the employer as to which standards to utilize for ensuring compliance but more importantly, that the workplace is safe for his/her employees.

OSHA defines “construction work” as:  “work for construction, alteration, and/or repair, including painting and decorating.” [29 CFR 1910.12(b)]  Additionally, OSHA points out in one of its Letters of Interpretation (LOI): “Also relevant to the distinction between construction and maintenance are the Davis-Bacon Act regulations.  In essence, 29 CFR 5.2(i) defines construction work as ‘generally includ[ing] construction activity as distinguished from manufacturing, furnishing of materials, or servicing and maintenance work.’”  [LOI-Knobbs, Nov. 18, 2003]  A dictionary definition of “construction” is: “The act or process of putting together parts.” [Webster, 2000]

In the Knobbs LOI, OSHA refers to a definition for “maintenance” that was in one of its directives by stating: “In OSHA’s directive on the general industry confined space standard, the Agency stated that maintenance involves ‘keeping equipment working in its existing state, i.e., preventing its failure or decline.’” (emphasis added)  [LOI-Knobbs, Nov. 18, 2003]  In a LOI dated February 1, 1999, OSHA describes maintenance:  “Maintenance means keeping equipment or a structure in proper condition through routine, scheduled or anticipated measures without having to significantly alter the structure or equipment in the process.”  While this may clarify the difference between “construction” and “maintenance” in OSHA’s mind, it does little to clarify it for the typical scaffold erector or his/her employer.  Research indicates that OSHA has wrestled with the issue for some time since there is more than one Letter of Interpretation addressing the topic.

Before discussing what might describe a work activity as “construction” or maintenance,” it would be instructional to describe which factors do not determine whether the work activity is “construction” or not.  First the name of the company has nothing to do with the matter.  For example, just because your company is called Dave’s Construction does not mean that all your work is construction.  Second, who the employees are has nothing to do with determining the applicability of the standards.  Third, whether it is “in-house” employees or an outside contractor has nothing to do with the type of work being performed.

“Construction is not limited to new construction, but can include the repair of existing facilities or the replacement of structures and their components,” declares OSHA [ibid]  The project’s scale and complexity must be considered in making a determination.  The physical size of the object that is being worked on can be a factor.  It can be considered construction “because it is a complex task in view of the steps involved…” [ibid]  Probably the most clarifying statement is OSHA’s declaration in the Knobb LOI that “it is not the personnel which will determine whether work will be considered maintenance or construction, but the work itself.” In the same LOI, OSHA points out that while the work may be done during a scheduled “maintenance outage,” that alone will not qualify it as maintenance.”

Finally, in a LOI dated August 11, 1994, OSHA tells its Regional Administrators “where an activity cannot be easily classified as construction or maintenance even when measured against all of the above factors, the activity should be classified so as to allow application of the more protective 1910 or 1926 standard, depending on the hazard.  In such cases the situation should be issued in the alternative with the emphasis on the more protective standard.”   Wow!  That appears to say that if you are not sure, find a standard that fits the situation, no matter where it comes from.  How bizarre can it get?  Here’s how.

In a Letter of Interpretation dated April 17, 2006, OSHA was asked if permanent guardrails that were 36 inches high would suffice during construction in a “General Industry facility.”  The existing facility apparently had guardrails on its platforms that were an acceptable 36 inches high, in compliance with the General Industry requirements for guardrails.  However, construction was going to occur at this same facility. Subpart M of the Construction Standards requires that guardrails shall be installed between 39 and 45 inches.  Consequently, in this instance, OSHA stated that a temporary guardrail would have to be installed adjacent to the lower existing permanent 36 inch high guardrail to protect employees during the construction activities.  Justification for this requirement was that “construction activities often include carrying tools and materials that are heavy, awkward to handle, and, in the case of large materials, can sometimes block the employees’ view.”  In other words, if the employee is blindly stumbling along dragging heavy tools, he better have a higher guardrail.  Otherwise, it’s okay to have a lower guardrail for the permanent employees of the facility.  Amazing.

Keep in mind that the OSHA standards are minimum requirements and they are promulgated to address safety hazards in the workplace.    Since it is OSHA’s standards, it can manipulate and interpret them in any way it chooses.   However, for your protection, do what is right to protect yourself and your fellow employees, not only from hazards that may cause serious injury or death, but also from ridiculous interpretations, and ultimately, ineffectual citations.