telling old stories - part III

This is a story told by a colleague and it is a good one for the instruction of a professional attitude for new students.

On a summer job the engineering student was working as an instrument man for a consultant who was designing a water pipeline which had to go over many miles - from A to B. His summer job was to do a profile survey of the line for the pipe, which had been cut through the woods. The surveying was done by two crews with independent notes so that there would be a check of the results at the end of the line. I don't know if one crew began at end A and the other at end B, or if they went along together.

In any case, after spending several days in the woods (fighting black flies and mosquitos) the two crews emerged from the woods and as it was a little early to be picked up by the truck, they sat down and began to work over the levelling notes. It was discovered that there was a ten foot difference between the two sets of notes. What to do? It was too late to go back since they had been in the woods for several days, and there appeared to be no obvious indication where the error lay.

So, with the obvious spirit of probabilities before them, they flipped a coin. Lady luck did not favour their choice for the line was vertically ten feet in error!

I really can't remember what the final solution was but it is a good indication of what can happen on the simplest job. Students should be told this story and some discussion of the consequences of such decisions can be elaborated.

Another surveying story.

While a student I worked with F.D. Cow Company one summer on the construction of a large grain elevator in Quebec City. I was an assistant to the resident engineer, and when he went on his two week holidays, I became the resident engineer and the Montreal office sent down some other engineering student to be my assistant! At the time when the resident went on holidays we were in the middle of a slip forming job for the bins. There were 24 bins being built at one time and as the construction was continuous day and night, I was able to move from the night shift to the day shift and let the other student take the night shift.

One of the tasks that had to be done was to make a level loop around the structure to check on the settlements as the slip forming was taking place. A number of brass pins were cast into the foundation walls and it was only a matter of doing a level loop around the structure - from A to pin to pin to pin and back to A again. No real problem.

The elevator was being built on an old pier at Bassin Louise, where an Immigration shed was located. It was a busy place with box cars being moved back and forth, six ready mix concrete trucks going back and forth day and night,  deliveries of steel, and carpenters, saws, the usual chaos of a construction site.

I decided one hot day that this was the time to do a level loop around the structure. So, I hired a rodman and tone hot afternoon t ook the transit out to take the readings. It was hectic for the heat of the day was such that it was difficult to read the rod numbers in the telescope, then the concrete trucks left a cloud of dust in the air as well as obstructing the view. At one point I set the transit up beside the railway track and lo and behold a train with a couple of box cars came along. I remember looking at the slowly approaching train, then the transit, and tried to gauge whether the step on the side of the boxcar would hit the transit. It was close, but at the last minute, I hauled the transit out of the way, just in case. That meant another set-up.  Basically with the heat, the dust, the noise, it was not possible to complete the loop and so it remained for the resident engineer to do that job.

The resident was my friend the  Hungarian mining engineer who had a fine technique for surveying. After he returned from his vacation, and I told him about my troubles in trying to get some readings, he said that we would do it later.

About 19:00 or 20:00 in the evening when there were no trains, no heat waves to make the numbers dance in the transit, no carpenters around, no delivery trucks,and little dust from the concrete trucks, we made the level loop in about half an hour. This fellow had hands that were big enough that he could grab the tripod with both hands and after setting the legs could adjust the three levelling screws simultaneously with both hands.

I don't think that I ever did any survey work since that time. It is wise to know when one is outclassed.

Relations with contractors.

I think that every civil engineering student should work for a contractor to have an appreciation of what people are like. While everyone on a construction job has a role to play, some are a bit more agressive than others and it is useful to know this.

A grain elevator had a foundation that involved driving thousands ofwood piles into the ground under the location of the elevator. I think the piles were on 3 ft centres and it seemed that the gound was so compressed by all these piles that some popped up when new ones went down.

On top of this forest of piles there was a five foot thick concrete mattress. In the grain gallerys above the mat, there were 24 inch deep sumps to collect any water that leaked into the galleries. By some oversight, two of these were left out and a solid slab put in. I used to remind the contractor often that he needed to get a jack hammer to get the concrete out before it hardened too  much. But I don't think he ever did.

The head house is where the bucket elevators lift the grain to the top of the system. There it flows into a hopper, then a weigh scale, then to another hopper and then to spouts that take it to conveyors that direct it to the appropriate bin. This makes the head house very high = I think on the order of 200ft.  In this case the detailer of the reinforcement had used bars that were 40 ft long. For the basement walls, however, the forms were just 10 ft. high so that meant that there was 30 ft of rebar waving in the wind above the forms. It was difficult for the steel setters to handle  the steel as it was always moving back and forth.

So, the superintendent asked me if he could cut the bars above the top of the forms and use extra bars for splices. Looked OK to me so I said yes. The structure was 96 ft wide and had verical bars at 12 inches on centres. It the splice length was 36 inches that meant there would be an extra 576 ft of #6 rebar needed.

After two months an extra was submitted for 576 ft of #6 rebar which, I was told, "You told us to cut the bars and splice them. This is the cost of the splice bars." Of course as Sam Goldwyn one said, "A verbal contract is not worth the paper it is written on", I had no paperwork to back up what had been said. I was quite perturbed, however, the Resident engineer, who was more experienced in these matters said not to worry about it.

Every construction job requires extras which have not been thought of in advance by the engineers, or the contractor makes a mistake so at the end of the job there is often a balancing act that is done to redress the costs. My feeling is that the cost of two missing sumps in the basement of the galleries was equated to the 576 ft of #6 splice bars.

GIGO = garbage in, garbage out

Your comment about a certain amount of conservatism in engineering as being a good thing brought back to me the thoughts associated with the projects course I am assisting an architect with. He wants students to design new, daring structures and has one fellow working on a car park structure which has a rood consisting on 300mm of earth supported on a fibre reinforced film which is supported in turn on cables. Grass on the roof is not obligatory. My thoughts turn to practical matters: how to deal with the rain that will collect in the trough of the cable structure; how to keep the earth from sliding into the centre of the trough; on the side slope where the cables come to earth, how to keep that earth from sliding; how to ventilate the structure?

To an architect this is not a reality. His comment was that, "They can replace the earth every ten or fifteen years, or do maintenance on the structure every five years or so." This from a person who is living in a city where the structures are all masonry and have been standing for over 600 years and are still in use. I pointed out that this kind of design would involve a very heavy liability insurance on the part of the engineer/architect and builder, but such mundane matters do not seem to enter the equation. We are, after all dealing with student projects. This seems strange for the students in their projects have to have two structural systems in place for the project and they have to agree with all the current norms for design and construction. If a professor looks at this cable supported roof with grass growing on it I imagine the mark will be close to zero.

My wife has just sent me an e-mail with the comment that the multi-million roof on the Olympic stadium in Montreal (Canada) has (again) self-destructed. It is a cable supported thin film structure - need I say more?

As you say, in our business conservatism is necessary.

Failed Research

As a graduate student I was given the task of completing a survey of the literature on "Limit States Design of Concrete Structures". This was done during the summer, and my companion in the library was a professor from the University of Ottawa who had embarked on the subject of composite steel beams as a potential research area. Earlier, while at the University of Manitoba, he had conducted some laboratory tests on this subject for the Manitoba Department of Highways, using large-scale specimens - concrete slabs 6 ft wide on steel beams 30 ft. long. I don't know what aspect of the problem he was studying, but he came to UNIWAT with some idea of what he would do and where he would go with it.

His approach to library research was interesting. We would both pull books from the shelves and search through the indexes for likely papers. Where I would list the titles and a few comments on index cards, he, having transferred some research money from the University of Ottawa, passed in 10 or 20 journals marked with slips to have the relevant articles xeroxed. Every day, he got 10 to 20 xeroxed papers, which he took back to his room in residence at the end of the day. Of course it was not very long before every horizontal surface in his room was covered with xeroxed papers. He read them all, and prepared a summary of the contents. At the end of the week, he prepared a summary of the summaries so that in time, he had on just a few sheets of paper the results of his library research, but backed up with the copies. By the middle of the summer, I don't think there was anyone more knowledgeable than he on that topic.

That summer there appeared at UNIWAT, an academic from Cambridge University who, we were told, was an expert on composite steel beams. My colleague's supervisor suggested that this visitor could give him a lot of excellent advice.  I remember the talk the expert gave. He described in detail the research work that had been done at Cambridge (England, not Massachussets). His specimens were all tabletop size. Miniature models scaled down to beams that were 12 to 18 inches long with micro concrete slabs. After having dealt with 30 foot steel beams and 6 foot wide concrete slabs, this was laughable to my colleague, and he got into a rather heated discussion period with the visitor over that aspect of the research.

The upshot was, and my colleage was a rather earthy fellow, "F*** them, they don't have a clue about the real world here." and left for home at the University of Ottawa at the end of the week. I have no idea if he ever followed up that line of research.

Unit conversion

Ratio of an igloo's circumference to its diameter: Eskimo Pi

2000 pounds of Chinese soup: Won ton

1 millionth of a mouthwash: 1 microscope

Time between slipping on a peel and smacking the pavement: 1bananosecond

Weight an evangelist carries with God: 1 billigram

Time it takes to sail 220 yards at 1 nautical mile per hour: Knot-furlong

365.25 days of drinking low-calorie beer because it's less filling:1 lite year

16.5 feet in the Twilight Zone: 1 Rod Serling

Half of a large intestine: 1 semicolon

1000 aches: 1 kilohurtz

Basic unit of laryngitis: 1 hoarsepower

Shortest distance between two jokes: A straight line. (think about it for a moment)

453.6 graham crackers: 1 pound cake

1 million microphones: 1 megaphone

1 million bicycles: 2 megacycles

2000 mockingbirds: two kilomockingbirds (work on it....)

10 cards: 1 decacards

1 kilogram of falling figs: 1 Fig Newton

1000 cubic centimeters of wet socks: 1 literhosen

1 millionth of a fish: 1 microfiche

1 trillion pins: 1 terrapin

10 rations: 1 decoration

100 rations: 1 C-ration

2 monograms: 1 diagram

8 nickels: 2 paradigms

3 statute miles of intravenous surgical tubing at Yale University Hospital: 1 I.V. League

100 Senators: Not 1 decision

Never look back, they might be gaining on you ...

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