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What Would You Like to Know?

DrD

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What Would You Like  to Know?

If you could ask me any question you want, what would you like to know that you think I might know? I certainly do not know everything, but through the years I have accumulated a certan amount of knowledge that I'd like to pass on to you. Therefore, I ask, what would you like to know?

Many readers are still in college, and no doubt they would like to know what is going to be on the next exam. I'm sorry, but I have no way to know that. What I might be able to tell you is some examples of where your present studies might be useful in the future. I recall my own student days, and I often wondered, "Where am I going to need to know xxxx?" I simply could not imagine where xxxx might arise in the future.

Other readers are out of college and in the industrial workplace. Some are doing fine with the knowledge they acquired in school, but others are discovering that they need knowledge and skills that were not taught in college. I know that this certainly happened to me. When I went out into industry, there were all sorts of problems that had never been mentioned in my college days and presented me with new learning challenges. That is a part of being an engineer; your whole career is a learning experience. At the same time, there are many situations where you might like to ask someone with more experience about a particular topic.

So, I repeat, "What would you like to know?" Please comment on this blog post and give me your thoughts.

DrD



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I have analyzed trusses for class work, but never in professional practice. In homework I am given the geometry and the applied loads, and asked to find the loads or stresses in members, not too difficult. But coming from a blank paper where do you start to design a truss or bridge, with so many types to pick from? For a simple beam I know what to do. For a complex truss, vs suspension bridge how is this decided before all the detail analysis starts? In the attached photo the bridge over the RR tracks (right side) is a truss. Over the road way a different type. I assume the RR  needs more clearance and puttinging the "depth of the beam" above the road way, provides the clearance. But why not a truss across the entire span, or the other type raised higher and extended. I assume there must be a significant cost difference but I have no practical experience to support this. Also I have seen bridges with a truss as show then other with the truss under the road bed or tracks for RR bridge. What drives the design?

Bridges.png

Bridges truss under.png

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Well, I got one good comment from JAG. I presume that means that he and I are the only folks left who don't know everything. I suppose that stands to reason; we are both old men! I had no idea the rest of you were so brilliant and over-informed!

To answer JAG's question, "What drives the design?" let me respond by saying "many factors." We might consider --

* cost and availability of materials (steel, concrete, stone, etc);

* cost and availability of a work force familiar with construction in various materials;

* cost and availability of machines to fabricate and erect the various bridge types;

* local and national laws and ordinances regarding height of structures, visibility blockage ("must not interfere with airport approach," "don't block the view of the mountain or the lake");

* past experience of each designer/erector (some have never worked in steel but have lots of experience in concrete and vice versa);

* opinions on aesthetics of various bridge types (suspension bridges look graceful, etc),

There are probably some more factors, but this is a start.

DrD

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