In chapter 6 Petroski relates that more conservative engineers will base their designs upon those that have been successful in the past, and those who are "structural artists", who are also concerned with the attractiveness of the site will try to do something new or different. (p.74) The railroad and the Maillot bridges above I think illustrate this point well. In driving through an area, I would most likely hardly take note of the railroad bridge. The Maillot bridge would probably make me want to jump out of the car and take a picture. Both bridges seem to perfectly fulfill their function, or do they?
When I tripped over the image of the Maillot bridge, it really made me stop and think, what truly is an "ideal" bridge? The physics of the problem I believe, is to create a structure that will evenly distribute the weight and pressure put upon it in such a way that there will be no stress or fatigue. Both of these structures seem to do this. Is there more to it?
There were two things that struck me in chapter 7 that made me wonder about this question of bridges. On p. 75 Petroski states, "Judging what works is always trickier than what does not..." I thought about this point for quite a while. This thought seems to apply to everything. Humans have a sense of what is generally unacceptable in most circumstances. Understanding what is, or could be considered acceptable is trickier to pinpoint.
On p.78 he goes on to say that engineers, "....decide when they have caught all of its major flaws and when it is as close to perfection as they can make it without working beyond reasonable limits." This is a tough call to make. I have seen students agonize over handing in a project, because they feel that it isn't quite complete. I myself, agonize, to a lesser degree :) about hitting the "publish" button on this blog, because I am not sure I have effectively communicated my ideas.
So, in thinking about my classroom, what is "the ideal bridge". What is it that differentiates one paper/project from another? I believe it is the difference between the project that fulfills all the requirements, and the one that shows a depth of insight and understanding beyond what is expected. How would you define "the ideal bridge"?
There is an old saying, "It's time to shoot the engineer and put the product out the door." This aptly captures a key issue in engineering (and elsewhere of course). It certainly applied when I worked as an engineer, and it works for me personally when I write books.
ReplyDeleteIn my experience of being an engineer (BSEE in 1976), I have always found it easier to judge what won't work than what does (even if I don't have sufficient expertise to know the difference).
Engineers who go against the flow are often chastised (just like being bullied in school). How much do you want to bet that the designer of the first cable stay bridge (e.g., Pennobscot Narrows bridge going across the Penobscot into Bucksport, http://www.maine.gov/mdot/pnbo/) caught a lot of grief? On the other hand, Apple (iPhone, iPod, iPad, etc.) continually goes against the flow and is largely impervious to such criticism, perhaps because they make sure that their designs are so well thought out and robust.
When I grade the work of undergraduate engineer students, I always differentiate "between the project that fulfills all the requirements, and the one that shows a depth of insight and understanding beyond what is expected," with higher grades being given to the latter group.
Realistic engineers would say that "the ideal bridge" exists only on paper. Students struggle with this all the time. They use 10 digits of accuracy in calculations when 3 is more than sufficient because of uncertainties that are inherent in the real world. Then they get upset when points are taken away for using such unrealistic high accuracy. Back in slide rule days, this was not an issue--everyone understood limited accuracy!
I love your comment about "shoot the engineer"! I have a friend who is an author and I would bet that editors want to "shoot the author" quite frequently as well. I also thought of the Penobscot Narrows Bridge while reading these chapters, however I did not know that it was the first cable stay bridge. I find that design truly beautiful and am thrilled that the designer "went against the flow" and took the risk to build it.
DeleteAs far as the classroom is concerned, we are truly on the same page. It is a challenge to get students to realize that more is not necessarily better. I'm going to go get my slide rule and show my daughter how to use it! Thanks for reminding me that although technology allows us to do things more efficiently, in many ways, it does not usually change the quality of the product.
And technology does not always help us really understand what something means. It may just show that we know how to push buttons correctly, as with a calculator. But ask the student what that number, their answer, means and they may have no clue. My thinking is teach the basics, the foundation, for true understanding. Then introduce the "quicker" way to calculate. Don't introduce the calculator first.
DeleteI have never used a slide rule but I am going to learn now!
I am sorry, I did not mean to say the the Penobscot Narrows Bridge is the first cable stay bridge. It was not, but as a whole cable stay bridges are a recent creation compared to suspension bridges and others that have been built for at least a century.
DeleteWhen I took Physics in high school (1975), we used slide rules and had to keep track of the decimal place. We had to learn about orders of magnitude, and three digits was usually sufficient without an in-depth study of significant figures. An interesting experiment would be to have one class use sliderules (antique stores??) and one use calculators and see if there is any difference in depth of understanding of results.
DeleteMy grading (and therefore my value system) has moved toward the "C" meets the requirements, but analysis and critique are required for better grading, and an "A" requires depth of understanding.
Students and teachers all struggle with deciding when something is ready to be passed in; a huge problem for perfectionists! Establishing due dates helps, but I have to keep them a bit flexible for the project that goes beyond the scope but has great depth and requires a little more time. As my friend Mary once said "Life is a F#@%ing Compromise".
Here is a link to the most astonishing bridge EVER! (In my middle schoolers' collective opinion)
ReplyDeletehttp://www.teachersdomain.org/asset/eng06_vid_incabridge/
Kelly, I just watched the Inca Bridge video...amazing and they can build them in 3 days!!!!
DeleteI agree with your middle schoolers and will also share this with 4th and 5th grade teachers in my school. Thanks for posting that.
That was an amazing video.
DeleteI just sent the link to our staff. Students regularly build bridges and this would be super footage for them to watch. Thank you!
DeleteGreat video, Kelly! And you can really see how these bridge builders had to work within the "specifications and constraints" of the environment!
DeleteThe "ideal bridge" would be one that meets all the standards. It would meet the needs of all who would need to cross it and yet challenge some too. Tne bridge would take into account that some travelers may need assistance moving across and others may zoom right across. I think the "ideal bridge" would have to be reconstructed periodically to accommodate changes in the environment.
ReplyDeleteI love your perspective. So as the teacher, our "ideal bridge" is the lesson/project/rubric that allows all children to learn and be successful. I know you're right. My bridges need constant maintenance to be adapted to the ever changing needs of my learners.
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