It’s official: the construction management textbook Soils in Construction, Fifth Edition by W.L. Schroeder, S.E. Dickenson and D.C. Warrington is now at Waveland Press. As someone who has dealt with contractors for his entire working career, I know that an understanding of the essentials of soil mechanics and foundations is crucial for successful–and profitable–completion of […]
What a “college man” used to look like, in this case my grandfather, C.H. Warrington, who is at the right. He started out at the University of Illinois but ended up at Lehigh, where he graduated with a Civil Engineering degree in 1912. (It was another eighty-five years before a member of the family would obtain another civil engineering degree.)
Lehigh is best remembered in engineering academia as the birthplace of Tau Beta Pi, the premier engineering honour fraternity, and gave the fraternity its seal brown and white colours. However, my grandfather wasn’t the Tau Beta Pi type, let alone a member; he was more comfortable with what was referred to as the “Gentlemen’s C.” My experience teaching has informed me that the Gentlemen’s C is very much alive and well in engineering!
Tau Beta Pi
Speaking of engineering’s premier honour fraternity, below is an account of the founding of Tau Beta Pi, from the 1912 Epitome, Lehigh’s yearbook (pp. 199-200):
THERE exist in the college world three well-known societies, membership in which signifies college honor, in the manifestation of high scholarship. They are Phi Beta Kappa, Sigma Xi and Tau Beta Pi. The first of these finds its membership in the men pursuing literature and the arts. The second selects its men from those who have shown distinction in the sciences and who have performed some research work. The last, Tau Beta Pi, of which we write, enrolls the honor men in engineering courses. Of the three Phi Beta Kappa is the oldest, having been founded in 1776, while the dates of founding of the other two were separated by only one year-Tau Beta Pi, 1885, and Sigma Xi, 1886. The existence of Tau Beta Pi is owed to Prof. Edward H. Williams, Jr., an alumnus of Yale and of Lehigh where he became Professor of Mining Engineering and Geology. The motives leading to and the circumstances attending the formation of this society are interesting and worthy of record in a book of this nature.
As valedictorian of the class of 1875 at Lehigh, Prof. Williams had been elected an honorary member of the Sigma (New York) chapter of Phi Beta Kappa, and was anxious for the establishment of a chapter of that society here. There were, however, two obstacles standing in the way, first, the fact that the council, in whose hands the granting of charters lay, met only once in six years, and, second, the strong objection in Phi Beta Kappa against the admission of technical men into its membership. Owing to the highly technical character of Lehigh’s courses the likelihood of an establishment of a chapter here was very slight and even with a charter granted the membership would be confined to a very small number.
Prof. Williams was aware of the necessity for the recognition of a man’s ability other than the diploma which he received, and further that the recognition should be given while the man was still at college, and not as he was just passing out through her portals. The attitude which some men had towards a diploma can best be shown by the following incident: As the valedictorian of one of the ’80 classes came from the stage after graduation Prof. Williams congratulated him, to which he received the reply” …… ‘s got one too.” The fellow in question had flunked every examination in his four years of college. There was no limit to re-examinations in those days and he had taken enough until he had passed.
These were the motives leading to the formation of the society. The details of organization are briefly given as follows: Prof. Williams’ conception of the society was that its membership should be taken from those men whose grades showed them to be in the first quarter of the class. Their rating must be above 75% and they must have no conditions. In practice this was to work as follows: At the end of their Junior year the men standing in the first eighth of their class became eligible for election and at the beginning of the Senior year the first quarter of the class became eligible. The election of these men, however, was not to be on the basis of scholarship alone but in addition the men must possess high morals, qualities of good fellowship, and manifest a healthy interest and rational participation in college activities.
To start such a society so that election into it would be sought and so that its .establishment would be firm and give promise of vigorous growth was a matter requiring much careful work. How this was accomplished is best told in Prof. Williams’ own words, and we quote from a letter from him on the subject, giving the Editor of the EPITOME this information on request.
” …… Now, too many cooks spoil the broth of society building; so I decided to take nobody into my confidence. I knew what I wanted and I went to work alone.
“I first drew up a constitution and provided for granting new chapters, for an executive council, and for alumni advisers to act as a balance wheel to keep things going in line, and I made it hard to amend this instrument. I then drew up By-laws for Lehigh.
“Next, there must be a body of alumni behind the affair before the first undergraduate was let in. I delivered the valedictory for ’75 and so was eligible to the society. I took the old faculty records and calculated the standing of every man who graduated, during his four years; drew up a list of the men in the order of their stand. They must be in the first fourth of the class and also have a general average of 75. Having the eligible men of the past, I had Edwin G. Klose, of the Moravian Book Concern, buy a series of special fonts of type, which are now in the possession of the society, a lot of electrotypes of the society key, and some other matter and print a lot of diplomas. . ….. I signed them as secretary, to which office I elected myself. The answers I received from the boys were refreshing. One valedictorian said he would value it more than his diploma.
“Then I had my friend Newman, of John St., New York, file out a society key, to see how the thing looked. Then I was ready for the undergraduates. I went slowly, however, and it was May, 1885, before I told Irving A. Heikes, the best man in ’85, to stop after recitation, one morning, and asked him if he would like to be the first undergraduate to join a society. He wanted to think it over, and finally said ‘Yes,’ so I initiated him. He took post-graduate work, I think, and in the fall he and Professor Meaker, who helped me initiate the classes for several years, and Duncan, ’80, initiated the men from ’86 and the Wilbur man from ’87.
“For several years I was elected president of the society and directed the body till it began to have a good number of alumni and many representatives in the Faculty. It took like hot cakes and soon its elections were looked for. “I wanted to have Tau Beta Pi in full blast before Phi Beta Kappa came, as it would not then be looked upon as an imitation by a lot of men who could not get into the latter. In deference to the general tradition I limited the membership in Phi Beta Kappa to students in the liberal courses, and I had the charter given to a council of a few graduate members, Mr. Kitchel, Albert G. Rau, myself and a few others.
“This is the way Tau Beta Pi came to Lehigh. It was the culmination of a lot of work covering four years. I could not give as much time to it as I wanted, owing to the growth of my department. Breckenridge was elected an honorary member. Heck became president and a ‘member of the advisory board, and then it began to form chapters outside. While the founding is wholly my own unassisted work, the spread is due to others …….. “
In June, 1910, the society had a membership of 3680 divided among 24 flourishing chapters, located at institutions of acknowledged leadership in the instruction of engineering. The twenty-fifth anniversary was celebrated here at Lehigh last June and the attendance and enthusiasm in connection with the convention gave every evidence of the solidity and prestige of Tau Beta Pi. J. L. B.
The response to the shock has been to turn campuses into kindergarten. The University of Michigan Law School announced a ”post-election self-care” event with “food and play,” including “coloring sheets, play dough [sic], positive card-making, Legos and bubbles with your fellow law students.” (Embarrassed by the attention, UM Law scrubbed the announcement from its website, perhaps concerned that people would wonder if its graduates would require Legos and bubbles in the event of stressful litigation.)
I don’t know what they did in Knoxville, but this is the message we got in Chattanooga (both of us teach at the University of Tennessee):
The Office of the Dean of Students recognizes that individuals on all sides may be trying to process and understand this election season. A lot of anticipation has been building up for many of us over the past few months. Many of us may be experiencing a range of emotions, both positive and negative, leaving us feeling drained. While we do not have the answers or possibly even the right words, we want each member of our community to take time to acknowledge what they may be feeling and remember the importance of self-care. For each person this may look different–some need to unplug from media, engage in physical activity, eat a balanced meal, or surround themselves with a community of support.
This was followed by a long list of campus activities, most of which were already on the schedule.
I teach civil engineering. Engineers in general and civil engineers in particular are in an interesting place because, when the government spends money on infrastructure, civil engineers benefit. So our relationship with the state is a little different. OTOH, that effort makes society more productive and raises living standards.
One of my students was expressing a little disquiet about the results of the election. My response: if Trump comes through with his promises to improve infrastructure, we in the civil engineering community will be busy and paid. That thought lightened the discussion considerably.
Trump promises to “make America great again.” You can’t make the country great only by improving infrastructure, but the country won’t be great without it. We’ve been burned before on this issue; show us the money and commitment, Donald Trump, and things will move a long way forward.
On my companion site vulcanhammer.info, I have posted several articles on Soviet (and after that Russian) pile driving equipment, such as diesel hammers, concrete pile cutters, and vibratory and impact-vibration hammers. These are very specialised topics, even by construction industry standards; here I want to present some photos of more general interest to you heavy equipment fans. The Soviet Union was known for its commitment to heavy manufacturing and construction equipment like this is certainly a big part of that.
NPO VNIIstroidormash is the Soviet name for the Moscow-based institute which designed and tested the equipment shown below. The name means the All-Union Scientific Research Institute of Construction and Road-Building Machinery. It was put together in 1975, and survived past the end of the Soviet Union in 1991 as a share society, i.e., a privatised corporation. In addition to the pile driving equipment which got me involved with the organisation, it designed many other types of equipment, and the best way to show this follows, from their catalogue produced around 1986.
Our family business first connected with the Institute in 1988, and our contacts continued for the next six years. Sometimes things got strange but we discovered an organisation that put out some very good designs for construction equipment. Unfortunately the Soviet manufacturing organisation was not up to proper quality control, especially in the civilian sector, and that weakness was one of those which ultimately brought the Soviet Union down.
One of pot shots that Hillary Clinton and her operatives made at conservative Catholics is that they used terms like “subsidarity” that no one understood. Since they may be right about that, I think an illustration is in order.
Many of you know that I teach Civil Engineering. Six years ago, my department head (who is from Kenya) and his first assistant (who is from the Cameroon) sat me down and asked me to obtain my PhD so I could teach more courses. I agreed and six years later, as W.H Auden said about Tolkien, at the end of the quest, victory.
In the course of the conversation, my department head brought up the subject of why potholes don’t get fixed in Africa the way they do here. (I know we have issues here.) His explanation was this: here, the local authorities (city, county, state) maintain the roads and, since they’re closer to the problem, they have greater incentive to fix it. Back home, decisions are made in the capital, and since they’re far away from the roads, they don’t have a pressing interest, and the potholes remain. That’s probably the best illustration of the concept of subsidarity—which seeks to push decision-making down to the lowest level—that I’ve heard.
Roman Catholicism—especially in its Ultramontane form, which has been the norm since the Restoration—is not the most suitable vehicle to promote the idea of subsidarity. It’s a good theological concept, but the structure of the church works against it.
As far as Hillary Clinton is concerned, truth be told, her problem with subsidarity isn’t that she doesn’t understand it. Her problem is that she doesn’t like it. Her idea—one that has been obvious since Arkansas’ educational “reforms” in the 1980’s—is that power and decision-making be concentrated at the top. People who support subsidarity are political enemies, which is a big reason she wants a “Catholic Spring.”
As far as how two Africans got a Palm Beacher like me to pursue a PhD, it’s another sign that, in engineering, we really do have change we can believe in.
Ever since people set out to sea in ships, the issues of buoyancy and stability have been of importance. In spite of this, the treatment it receives in textbooks is often lacking. Following is an overview of the subject; basic understanding of the principles is essential in performing the experiment and interpreting the results.
Buoyancy is ultimately what makes things float, such as the buoy in Figure 1. This is true whether the material the boat is made of is lighter than water (like the balsa wood rafts Thor Heyerdahl and his crew crossed the Pacific with in 1947) or heavier than water. The latter would include objects from the buoy shown to the ships of the U.S. Navy.
The basic concept is very simple: for anything placed in a fluid medium, the upward force the medium exerts on the body is equal to the weight of the fluid the body displaces. This is not only true of bodies placed in water; it is also true of those in air. The difference is that, for those in air, the weight of the air displaced is usually not enough to “float” the aircraft. A notable exception are dirigibles such as the “Goodyear blimp,” which is filled with helium, a gas lighter than air. Another lighter-than-air gas used is hydrogen. This is very combustible, as everyone was reminded of when the Hindenburg caught fire in New Jersey in 1938.
Most buoyancy applications are marine ones, and it is those we will concentrate on in this experiment. We will also concentrate on rectangular forms and flat-bottomed vessels, which simplifies the math somewhat. However, these principles can be extended to just about any floating craft.
Using a flat-bottomed craft also makes it easier to understand why displacing a fluid works. Consider first the following: how the force of the fluid on the flat hull of a craft varies with depth1:
For a fluid at rest, the hydrostatic pressure increases linearly with depth, thus
where p is the hydrostatic pressure, γ is the unit weight of the water, and D is the depth from the water’s surface to the bottommost point of the vessel, usually called the draught. This distance from the water line to the top of the rectangle (the gunwale) is called the freeboard; the results of inadequate freeboard can be seen in Figure 3.
In any case, for a vessel of beam (width) W and a length L the volume it displaces is given by the equation
Combining and rearranging these two equations,
For the boat to float, it has to be in static equilibrium, and so the downward force of the weight of the boat Wboat must equal the upward force Fbuoyant. Therefore,
So we’ve established a relationship between the weight of the boat and the volume of water it displaces. The “far right” hand side only applies to boats with a flat bottom and straight sides.
What this means is that there are three ways we can weigh an existing boat:
We can simply weigh it on a scale. For small boats this isn’t too difficult; larger ones can be tricky. We can then estimate how far it will sink into the water.
We can measure the freeboard, then obtain D and, knowing L, W and the unit weight of water, we can compute the weight of the boat. This works easily for rectangular boats; for real boats, you have to determine the relationship between the actual waterline and the displacement, then see where the actual waterline ends up.
We can use an overflow method, which is okay for small experiments (like Archimedes used) but not so hot on a larger scale. But this illustrates our concept.
Procedure for determining volume of water displacement2:
Buoyancy is a fairly straightforward concept, although it may be a little hard to grasp up front. Stability—the ability of the ship to resist overturning—is a little more difficult, although it’s obviously important, as the following diagram of a ship with waves coming at the beam shows3.
Let’s define (or recall) a couple of terms.
Centre of Gravity: this is easy, mathematically this is the centroid of the mass or weight of the ship. An illustration of this is below.
Centre of Buoyancy: this is a little trickier, this is the centroid of the cross-sectional area of the ship under the water line, as shown below.
As you can see, for a box-shaped vessel which is not listing (i.e., leaning at an angle) or has no squat (i.e., not angled along the length of the boat) the centre of buoyancy is located halfway down the draught of the vessel, halfway across the beam, and dead amidships.
The centre of gravity and the centre of buoyancy are not necessarily at the same place; in fact, they are usually different. That difference determines both the stability of the ship and, literally, how it rolls.
We know that motor vehicles with high centres of gravity (such as off-road vehicles) are more prone to turn over in use than those with lower centres of gravity. Ships are the same; we need to have a way to decide how stable a ship is and whether there is a point that a ship becomes unconditionally stable or unconditionally unstable.
As long as a ship is upright, and both the centre of gravity and the centre of buoyancy are in the centre of the ship in all respects, it is theoretically possible for a ship never to turn over. As a practical matter this is impossible; even very large ships like cruise ships, which use their size to resist roll in most wave situations, are going to roll some. Below is a diagram which shows the centre of gravity and the centre of buoyancy for a ship which is upright and which is inclined 14º.
We need to look at this carefully and note the following:
The point G is the centre of gravity of the ship.
The point B or B’ is the centre of buoyancy of the ship. In the course of inclination the centre of buoyancy will change because the shape of the cross-section under the waterline changes; this is fairly simple to calculate for rectangular ships and more complicated for curved hull shapes.
The point M is the metastatic point of the ship. The distance GM is called the metastatic height of the ship.
If point G is below point B or B’, the ship is unconditionally stable; it will not turn over unless G and B’ is changed by taking on water, shifting cargo in the ship, etc.
If point G is below point M, the ship is conditionally stable, and if point G is above point M, the ship is unconditionally unstable.
The reason for this last point is simple: the ship above is rolling in a clockwise direction. The resisting moment of the buoyancy, calculated by (GZ)(Wbuoyant) is counter-clockwise, as the buoyant force is upward. This is true as long as G is below M. If G moves upward above M, then the now driving moment (GZ)(Wbuoyant) turns clockwise, the same direction as the rolling of the ship, and the ship will generally turn over4.
Thus the location of M, abstract as it may seem, becomes a critical part of the design of a ship. But how is it done? There are two methods we will discuss here of determining the metastatic height of a ship.
Determining Metastatic Height
This method uses the following formula to determine the location of the metacentre:
For a rectangular vessel, the moment of inertia is the same as we used in mechanics of materials, i.e., LW3/12, and is applied as follows:
The displacement volume was given earlier. We then compute the distance between the metacentre M and the centre of buoyancy B as follows:
Note carefully that this is NOT the metacentric height GM; it is then necessary to subtract the distance from the centre of buoyancy to the centre of gravity from this result to obtain GM. This is done as follows:
It’s worth noting here that the location of point M is independent of the centre of gravity and dependent upon the geometry of the ship and its volume under the water line (or total weight.)
Timing the Roll
This method is sort of an “old salt’s” rule of thumb method. First, let’s define the roll time. The roll time is the time it takes for a ship to start from rest at an angle of roll (port or starboard,) roll to the opposite side, and return to the original orientation. This can be approximated by the equation5
where tr = roll time of ship, seconds
GM = metastatic height of ship, meters or feet
W = beam of ship, meters or feet
C = constant based on units of GM and B
= 0.44 for units of feet
= 0.80 for units of meters