Related to today’s column about inferior or counterfeit bolts, the new San Francisco-Oakland Bay Bridge had a batch of nearly 300 bolts that snapped after in situ testing due to something called hydrogen embrittlement. Some of these fasteners are 3 inches in diameter and up to 24 feet long, so perhaps calling them “bolts” as if you could buy some at the hardware store is a misnomer, but they are threaded fasteners. Must have been a hell of a bang when those monsters snapped.
Since this thread is about today’s column, I will add this comment here, instead of creating a new thread just to get it merged later.
I just wanted to expand on Cecil’s explanation of the “Jesus Nut” in military parlance. The Jesus Nut on a helicopter is the colloquial name for the nut, or system of nuts, that hold the Main Rotor onto the drive shaft. Failure of the Jesus nut means departure of said rotor from said helicopter, and yes, you will be seeing Jesus real soon.
The term is in civilian use, too.
As a youth, I was told that the term came about because you pray to Jesus that the nut doesn’t come off.
Checking the ‘Jesus nut’ is part of the preflight inspection. Make sure it’s on, that the safety wire is intact, and that the paint markers are not broken. This is what always went through my mind: ‘If that bolt breaks, the rotor will come off. Best not to think about it…’
I believe the title on this one should be “Big Dig,” not Big dog" based on the linked article.
MODERATOR NOTE: I have changed the title from “dog” to “dig.” And I’ve merged this into the other thread on faulty bolts.
There was also a building collapse in Kansa City in 1981, the Hyatt Regency Walkway, caused by:
which is partially bolt failure, mainly because they decided to have one walkway not only support itself, but another below.
It seems a horrible story.
The bolts (actually suspension rods) did not fail. The problem was that the rod was supposed to be one piece, supporting cross-beams at intervals down its length, and the contractor built it so that there was an upper rod and a lower rod. The connection of the upper rod to the highest walkway was not strong enough to hold the weight of both the top walkway and the lower one, so it pulled through the supporting beam and triggered the collapse.
I spent a week at the KC Hyatt (which no longer has any “skywalks,” but you can see where they used to cross the lobby) and could never walk through the lobby without a shiver. How many other places can you stand where, at one time and in a small area, 114 people were killed? Most get torn down or blocked off. When I mentioned this to a KC friend who was at the same conference, she stared at me for a moment, pointed to a corner of the room and said, “I know. My aunt died right over there.”
I still shiver a little when my swing collection gets to “Satin Doll,” which was the tune they were dancing to (some on the skywalks) when the collapse happened.
During its construction, the David L. Lawrence Convention Center, designed by New York architect Rafael Vinoly, was touted as an “unconventional” building whose cable-stayed roof allows column-free exhibition halls.
Feb. 12, 2002 – Ten days before the first phase of the center is to open for the first time for a recreational vehicle show, a 90-foot-tall steel truss crashes to the floor, killing ironworker Paul Corsi and injuring two others. The collapsed truss is the 13th in the series of 15 steel support trusses.
June 5, 2002 – At a coroner’s inquest into the death of Mr. Corsi, metallurgist Robert Elmendorf testifies that he thinks construction workers used the wrong type of nuts to secure the truss in place. Mr. Elmendorf of Modern Industries Co. was hired after the collapse by the general contractor, Turner-P.J. Dick-ATS.
July 22, 2002 – At the coroner’s inquest, Mr. Elmendorf raises new questions about the quality of structural materials used to build the convention center. He says his testing showed that 30 anchor bolts used in the collapsed section were not adequately strengthened. Asked if he thought the bolts used in setting other trusses in the building were substandard, Mr. Elmendorf says there is no way to get an answer because those bolts are encased in concrete.
The column in question: http://www.straightdope.com/columns/read/3143/are-some-new-york-skyscrapers-held-together-with-fake-bolts It helps to include a link; a lot of us don’t bother reading Cecil’s column because we know everything already.
Chicago has had inclement weather lately, and the winds blew apart the sheets of Visqueen protecting a building under construction. My daughter expressed sympathy for the company whose new warehouse it will be. I said, “Not their problem. It’s the contractor’s problem.”
“Then I feel sorry for the contractor.”
I nearly had an accident but eventually recovered enough composure to both steer and say, “Don’t let me hear you say that again. You never, EVER feel sorry for a contractor. They are hellspawn and the bane of my existence.”
Contractors and engineers don’t mix. That quote shows why.
Titanic was built with substandard rivets, I believe. The solution was to decrease their spacing.
I mean, what could go wrong?
If you are involved at all in the construction industry, you are aware that counterfeit products exist; everyone knows that counterfeit products exist. Guess which country is at the forefront of shipping counterfeit products?
I know in the nuclear industry a metallurgical CMTR (Certified Material Test Report) from an independent laboratory is required before acceptance of structural or pressure boundary components.
The construction industry should be similarly regulated, however it requires diligence on behalf of the purchasing department, the incoming inspection department, and also the provincial (or state) regulator.
If everyone does his job it should be very difficult to introduce fake components, but I can see how mistakes in oversight can be made.
…and somebody who won’t blow it off when somebody else asks, “Who specced this shit?”
I’ve done purchasing, too. I’m a man of many talents, all of them half-assed.
Here’s how it should go:
The engineering drawing, independently verified by another qualified engineer, states the material and regulatory and quality requirements.
The engineering drawing is stamped by a professional engineer.
A purchase requisition is raised to the requirements of the engineering drawing.
A quality assurance representative ensures all the QA requirements are specified correctly in the purchasing req.
Procurement reviews the requirements, selects an appropriate supplier, and creates a purchase order.
The supplier responds with PO terms.
The PO is independently verified by another qualified buyer.
The PO is forwarded to PO Quality Assurance who reviews the file and the supplier qualifications and approves the PO.
The supplier ships the parts and paperwork.
At receiving inspection the parts are verified, and the Certificate of Conformance and independent Certified Material Test Report are reviewed for accuracy.
The parts are received into a secured location and marked physically, or tagged, with the PO number and batch/heat number.
The parts are signed out to a work order.
The work order and/or inspection and test plan are authorized by management and also by the provincial regulator, who places his own hold/witness points on the Inspection and Test Plan (ITP).
Operations Quality Control places their own inspection and or hold/witness points in the ITP.
The work proceeds with applicable signatories at required places, including independent peer verification.
Once completed, Work Management and Work Assessment management, along with Operations QA signs the completed work package, and in some cases a Project Engineering QA rep signature too.
The completed work package is reviewed for accuracy by the close-out rep.
Internal QA auditors audit the process on an ongoing basis to ensure compliance.
The provincial regulator audits the process on an ongoing basis to ensure compliance.
The federal regulator audits the process on an ongoing basis to ensure compliance.
This is how things like pipelines are built too. Which is why I have every confidence in newly-constructed pipelines.
ETA: Not to mention education and proficiency of everyone in the process are also audited on an on-going basis.
So how expensive is an independent CMTR? If legislation was passed to require it for extraordinary designs (and who defines what is extraordinary?) how much extra time and cost would it add to construction?
And when is it done? When the hardware is delivered or when it is about to be installed? This isn’t as trivial as it may sound - the Bay Bridge bolts sat somewhere for four or five years between being made and/or delivered and being actually used. Were they good when made, but deteriorated in storage?
If we’re talking “shoulds,” you missed:
a. The architect creates a rendering of his vision and rough sketches of how he thinks it will go together.
b. The architect and the engineer go over it in the absolutely vital “Do you think this is going to work?” meeting.
c. If necessary, the architect makes the subtle changes needed.
d. The architect presents the design to the client, gently explaining why the client’s suggestions will cause the building to collapse or cost twice as much to build.
e. The architect shows the changes to the engineer, who, after much shouting, hands it off to the drafters.
f. After much muttering, the drafters finally make the damn thing work.
g. The architect and engineer sign off on the drawings, taking full credit for the building’s beauty and majesty, and give the drawings to the contractor.
h. The contractor then does whatever worked the last time, or is simply easiest, or is just what he feels like doing while making the building look roughly like it did in the drawings.
i. With the building nearly completed, somebody outside the above group of experts realizes there are no washrooms.
The CMTR is performed not on the finished parts, but on the raw metal used to forge the parts.
It is possible to request a CMTR on a finished part, but that’s not the typical flow.
I don’t know how much it costs. It’s the cost of doing business. Structural components all require this, just as all structural welds require a plethora of inspection and regulation. I could type another paragraph on how welds are controlled; it’s very well regulated.
A lot of this goes back many decades, but standards are always being revised. I don’t know the history of the Bay Bridge bolts. The storage requirements are very well understood, and storage, traceability and material condition must be assessed annually.
MODERATOR COMMENT: There have been several threads on same topic. I’ve joined them together under a title that best represents Cecil’s Column (although I loved “Bad Bolts Bollix Bay Bridge” but it wasn’t noticed as comments on the bolt/skyscraper column.)
They say Roebling overspecified the Brooklyn Bridge by 900%. On the assumption that the suppliers would deliver crap.
Jesus joint - a single piece, the failure of which is fatal - thus “the only Savior”. This can be a nut, bolt, cable, screw, any fastener or item used as a fastener. You don’t want a design which uses these.
Think about the difference between the single spin-on nut used to hold wheels on Indy cars - having the ability to knock the spinner once and have the wheel off, replaced, and the nut back on in 8 seconds is handy in a pit stop. I like having 5 lugs on my wheels - those spinners are Jesus joints.
I think it was on these boards where an architect and an HVAC contractor got into the natural enemy mode.
It seems a convention center (IIRC) was found to be falling down rather soon. Inspection revealed that the HVAC people, needing somewhere to route the huge ducts required to ventilate the place, had cut massive holes in the 7’ transfer beams supporting the tower above the huge open space.
The KC catwalks was not a strength-of-the-suspenders issue. It was the more subtle issue that, as built, the walkway beam was required to carry the load. As designed, it was only required to support the pedestrians
| | | | | ---- vs. ------ | | | |
In the first one, there is no load on the horizontal member - as designed.
In the second one, the horizontal member is carrying the weight of the lower catwalk - as built.
Why the substitution?
The design required the rods to be threaded in the center - it was to be a single rod, passing through the upper catwalk (with a nut to hold the horizontal beam) and terminating at the lower.
2 small rods with threads only on the ends were MUCH cheaper and easier…