Many times lately, I hear that the recent increase in construction is causing a shortage of skilled workers resulting in an increased rate of workforce injuries and accidents. I don’t know the validity of the claim, but more than the typical number of prefabricated metal building structural failures have come to my attention within just the last few months. Two of these incidents involve complete collapse of structures very much identical to my own typical project. I am acutely obsessed with these circumstances.
Far from morbid curiosity, I have always made it a practice to follow construction accident occurrences and look for lessons that may apply to my own procedures. In particular, I consider prefabricated metal building erection related failures a valuable opportunity to evaluate if I may be exposing my crews to unanticipated risks. Complacency is a deadly state when it comes to any inherently risky process. Experience can work against you. When you have gotten away with something time after time, you may be led to believe a less than certain method is perfectly safe. It may well be, until it isn’t.
Two such incidents I am currently following are the SL Aviation Hangar collapse at Morristown Municipal Airport in New Jersey and the Argyle High School practice facility collapse in Texas. Both of these projects represent, precisely, the typical CMBSC project. We complete dozens of very similar projects every year. My take away at this juncture:
- Metal building erection is a risky endeavor not to be entered into without the appropriate training, experience and oversight.
- There is no amount of bracing and redundancy that is unwarranted. If there is a next level of preparedness, you should be there already.
- Near misses and incident reviews are learning opportunities. Don’t waste them.
Note: Several workers were injured in the course of the incidents discussed below. At the Argyle collapse, Julio Ledesman (36) was deceased as a result of his injuries. Mr. Ledesman was a father of 3 young girls, you may contribute help to the family at this link.
Admittedly, I have no first hand knowledge of either of these incidents and I welcome comments to correct any misconceptions presented here. I do have thirty years of direct involvement in the operations related to all manner of prefabricated metal building construction. I am regularly responsible to see that complex erection processes of significant scale and risk are planned and executed safely and efficiently.
SL Aviation Hangar
It seems they were in the initial stages of the old school “stick building” technique on considerably wide clearspan frames. There is very little detailed information that I can find and no video. It is apparent from the photos that both sidewalls were framed complete with mezzanines and all the secondary in place. I would expect that the lean-to frames, plenty of bracing and the mezzanines contributed quite a bit of added stability. A very good start and this surely gave them additional confidence as they assembled the rigid frames across from side to side.
At this stage of erection, the secondary framing and bracing are incomplete. The integrity of the structure throughout this risky process is at all times completely dependent on the judgement of the erector. There is no overstating the critical nature of the choices made with regards to hoisting sequence, temp bracing placement and the sequence of installation of each of the permanent struts, bracing and secondary components.
Without more information, I have to assume the erector neglected to provide for adequate temporary bracing or to install the appropriate critical members to ensure the stability of these frames in the race to complete the system. At this point in this operation, regardless of the conditions or the circumstance, it is clearly on the erector to have and to implement any and all necessary measures to ensure the integrity of the structure and the safety of the crew.
Not a lot to learn here, aside from a reminder of the importance of a well thought out plan for this type of process. In practice, at CMBSC we avoid this method almost entirely. We prioritize pre-assembly of fully braced bays on the ground greatly minimizing the duration of potential instability. On the rare occasion that site conditions or design prohibit our preferred grid build option, this incident will now serve as reminder to approach the operation with thorough planning, appropriate equipment and the greatest caution.
Argyle High School Practice Facility
Wake Up Call
This one scares me. To see a structure at this stage completely collapse, the realization that this is even possible, makes me highly uneasy. At this point in the erection process, I would expect risk of failure to be negligible and diminishing further with each day that additional components are installed.
Initially, limited photos and news stories left me with the impression that the erector had rushed to set too much structure in place with very little bracing. This is truly unfathomable for even a marginally competent operation and I wouldn’t by any means consider this as a conclusion without more information. Some weeks later now, there are many more photos, additional news publications and the school has released security video which shows the entire progression of the collapse from several angles.
I say again, that is really scary. I picture myself having been on that jobsite, completely confident that all is well, and then watching the catastrophic failure from the parking lot as I get in my truck. Nightmares ensue.
Reviewing the photos and video, I have some observations of note.
- They have what appears to be temporary pipe bracing to the inside flange of each column about half the distance to the eave. This is unusual and extraordinary indicating that the erector is not without consideration for safety. In fact, some may consider this going the extra mile to ensure stability of the side walls prior to setting the rigid frames. This leads me to doubt that they would not have x-bracing installed. I can’t see any x-braces in the photos but none of those photos have any decent resolution so there is no way for me to know for sure.
- The way the three forklifts are lined up across the bay at the center of the building caught my attention immediately. I am thinking that they may have been using them either as anchorage for temporary guy wires or to pull the frames and straighten the rafters. I am certain that there are cables running to those machines as I can see all three forklifts shift as the building falls. The center forklift front tires lift off the ground and then abruptly drop in the video footage between 15 and 18 seconds. The forklift on the right shifts just a bit at the same moment. In the next view, between 20-23 seconds, I see the left forklift rise above the hedge then drop.
- Something had to be pushing or pulling the structure over. There is a bit of wind, my guess is maybe 15-20mph based on the flag and the trees. In any case, at that stage of construction, even tropical force winds should be no real threat to an adequately braced structure. It almost looks like the farther boom lift may have run into a cable, causing it to pull on the rafter. I am guessing either this or perhaps they were intentionally pulling to straighten a racked frame.
- You can see a brace cable snap in the third bay on the video at 10-12 seconds. This is evidently the only cable on that left side wall, or the last to go. Once that goes, it’s all over. If that is the only bay they had braced, shame. Standard procedure is to install all the bracing possible at each stage of erection. This should be absolute first priority once having set each of the rafters or grids.
- Again the photos are grainy and details difficult to see but I can’t see any flange bracing installed at all. There may be some there, but I can’t find it. Flange braces are just one small component that greatly improves the overall stability and it is prudent to get them in place wherever possible at every stage of erection.
A wake up call indeed. Just the thought that a structure that far along, seemingly beyond the point of concern, can come crashing down on my crew. This thought will remain with me for some time and will undoubtedly be cause for some additional caution and consideration in my operation going forward.
When I am asked if I find it difficult to find good help, I count my blessings. I am fortunate to have, in my own opinion, the very best crew in the industry. The core of my team have stuck with me through thick and thin over many years. My crew is more than just a workforce. They are my extended family. I can’t imagine how it would feel to be responsible for a tragic loss or serious injury such as happened in these incidents.
Hopefully we can all take a moment to remember those that suffer and be reminded of our responsibility to ensure that each day our teams are working safely with a well considered plan and all the required training, equipment and oversight not only to get the job done but to get it done safely and to return home to their families same as they left.