By Spencer Erling, Education Director, SAISC
It is just three and a half years since the first article in the series was written, (see Volume 35 No. 2 2011, Some gems from Spencer’s Steel Enlightenment Course for Wits students), a whole bunch of courses later we have enough material for a follow up article. Our grateful thanks goes out to our “innovative but somewhat misguided students” usually in the form of (incorrect) answers to test papers
The courses are usually offered in the last week of the student’s vacation, either at year end or mid-year breaks. You would think that some of the students were working under extreme pressure or round the clock before attending the program (during vacation huh?) but more likely extreme partying because some of them walk in (quite often late) sit down and fall asleep even before they have to listen to one word of my, apparently to them at least, boring subject and delivery.
So it is no surprise that we do get the really garbage answers to straight forward questions from some of our not so good candidates. Of course as the lecturer you begin to question yourself and your (in) ability to get the message across… fortunately with experience you learn who these wonderful answers are coming from and can ignore their poor, sleep driven, performance.
The course is an attempt to introduce second year civil engineering students to the whole structural steel process literally from digging iron ore out of the ground to handing over the proverbial front door key. Part of the course is dedicated to field visits to tube makers, fabricators and to erection sites. Some of the questions are aimed at finding out if they have learnt something from these visits in addition to the lectures. All of the questions are straight forward multiple choice or one line answer type. There are no trick questions but we would like to know if the students can think broadly enough to “join some of the dots”
New welding theories
We spend a good two hours covering weld processes, types (fillet / groove), sizes, positions (flat, vertical up etc), defects and how to find those defects (NDT) but the emphasis is on the fact that we use either flux around or in the rod to create a gas
shield to keep the nasty’s in the air away from the molten pool (SMAW or FCAW) or we deliver a gas shield to point of welding (GMAW).
Upon being asked a question to which we would expect an answer along the lines just described some of the proposed new methods would be (sic)
• The use of Airtight welders (a pity about his need to breath…)
• Use a gun which has the ability to remove the gases from the welding pool (should we try a 45 magnum…???)
• Using a (paint) primer or other protective (paint protective to welding?) coating
• Submerging in water… and along similar lines
• Add water to the weld (to cool off the heat/ melt) (now that should keep the welder guessing just who in the process has gone crazy)
When asked to describe some common weld defects (expecting an answer like cracks, lack of fusion, shape and or size of the weld, distortion) the latest defect is…
• Ingots (yup I guess an ingot could do some real damage to a weld…)
When asked to explain how the welding up of tubes along their length in a tube mill differs from normal (SMAW, GMAW, FCAW, SAW) methods we expect an answer along the lines that induction welding using heat and pressure only and no filler wire is used in tube mills. Tube makers here is new one for you to try (sic)
• The hollow section is fed with carbon from within the tube and melted by heated arc to form the weld
Yes we all know there a lots and lots of issues around bolts, bolt grades, new bolt specifications and, and, and of course tightening of bolts correctly. The SAISC has for a long time now followed North American methods of tightening HSFG and other preloaded bolts (rather than the torqueing methods adopted by European specifications). Clearly this is an important subject and receives it fair share during the (limited) time available. The turn of the nut method is described carefully and emphasised several times. So sure, one of the questions is to describe the method.
Now pay attention all of you involved in the process of pre-loading bolts. Stop wasting your time and energy you can just (sic)
• Weld the HSFG nuts
Fire protection issues
Why we need to passively fire protect steel and how we do it is the subject of one of the talks. The reason why is ascribed to the fact that at 600°C temperatures steel has lost 70% of it’s yield strength, something that usually leads to collapse. One of my favourite questions is why we passively protect our steel expecting the above explanation as an answer.
Readers in the opinion of one of our budding geniuses we have our theory totally wrong because (sic)
• The greater / higher the temperature degree, the higher the yield strength of steel.
We have been missing out on some readily easy to apply materials for passive fire protection. The latest suggestions are…
• Using a layer of copper around the structure since copper is a bad conductor of heat
And the winner by far…
• Galvanizing and mixing it with alloy to make it more brittle (shoo! I am clearly confusing them… must remember to try not to confuse them so much in future)
Some time is spent on the fact that steel rusts and that we need to prepare the steel suitably removing rust and other not desirables (i.e. wire brush, shot blast, acid dip etc) to receive paint, the role of prime coats etc.
We have lost out on a very common building material to assist with rust removal
• Concrete encasement
Metallurgists who might read these words of wisdom, did you know that the new role for prime paint is (sic)
• To get to know the quality of the steel
Naturally any good course on the structural steel process will cover how we enclose our structures (clad) and we cover metal, fibre cement, precast elements, glass and high density polystyrene (LSFB) methods but sadly we have been missing out on two readily available products (with apologies to our recycling industry…)
• Recycled cans
• Motor cars
Steel and concrete interfacing
Finally the course covers the interface between steel structures and concrete foundations and the need to create the ability to adjust the steelwork to suit the (often) incorrect holding down bolts. I emphasise the need for our steel to be adjustable. That is the answer I expect to the question I have occasionally set.
They get full marks for the one word “adjustment”
The following treatise received no marks… but does highlight how easily the students can confuse and mix the different parts of the course (sic)
• Transferring the loads through the base plate into the foundation by a method that wont allow the bolts and the base plate to easily corrode the concrete and create spaces in these connections. Adding a flux between the plate and concrete can do a lot to spread the load uniformly (at a guess he meant grout not flux…)
Finally a serious word of warning, do not apply or use any of the above theories or methods without extensive research and testing which I think would be a whole waste of time and effort. If you do, it is at your own risk.