We are assigned homework in Structural Analysis I (CEE 159) twice a week since we have lecture on Tuesdays and Thursdays. The longer homework is assigned over the weekend and usually is around 10 problems which take about 5 hours total. The “shorter” assignment is assigned Tuesday and due Thursday. This week’s short assignment was only 2 problems, easy right? We have been solving for deflection equations in beams using the double integration method. This basically means finding a mathematical equation for the shape of a beam after it has deformed under a certain loading. First, you have to find the equation for the internal moment along the length of the beam. Then you integrate it twice and pretty much get the answer. However, for the one problem on this homework, the beam given had five different sections with a different moment equation for each. When you integrate one of these equations twice, you get two integration constants. So that gives you a total of 10 unknown constants that you have to solve for using some boundary conditions you recognize. So this becomes a system of ten polynomial equations that you have to solve! What happened to me is that I finished solving the system for the constants only to realize I had written one of the moment equations wrongly. I decided to ignore it and continue onto the next part of the problem, solving for the maximum deflections, but then discovered that the answers I had found would not even give me a wrong answer. So I really had no choice but to go back and fix my earlier mistake. The time I spent redoing all the work added up quickly but I finally finished. I’m not even sure I have the right answer because with a problem of this length and complexity there are so many places to make one small error. It’s crazy to think that before there were computer programs that could do problems like this one for us in seconds professional civil engineers had to hand calculate the stresses, deformations, etc. of the complex structures they were designing. A small mistake anywhere could have resulted in a failed bridge or building, costing a lot of money and possibly even killing people.
October 30, 2013
Yes, I Spent 5+ Hours on a Single Problem
By lukarl15
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About lukarl15
Hey! I'm Karl, a civil engineer in my senior year at Lehigh University. I am from the Buffalo/Western New York area and am the president of the American Society of Civil Engineers on campus. I am also on the Running Club team, practice electric and classical guitar, and study music theory on my own. I enjoy playing and watching sports with my friends in my free time (or the times when I probably should be studying).
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This entry was posted on Wednesday, October 30th, 2013 at 11:16 am and posted in Civil Engineering, Structural Engineering. You can follow any responses to this entry through the RSS 2.0 feed.
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