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FrankLloydWrong
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Posted: Thu Aug 7th, 2008 05:07 am |
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Wondering if someone can concisely explain rollers as opposed to pins insofar as how it impacts structural concepts and/or calcs.
I have gotten so used to those little triangles and circles in the beam diagrams I've forgotten what they represent, and can't seem to find it in Kaplan or Ballast at first glance/ index search.
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StrongWilled
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Posted: Fri Aug 8th, 2008 02:06 am |
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FrankLloydWrong wrote: Wondering if someone can concisely explain rollers as opposed to pins insofar as how it impacts structural concepts and/or calcs.
I have gotten so used to those little triangles and circles in the beam diagrams I've forgotten what they represent, and can't seem to find it in Kaplan or Ballast at first glance/ index search.
Good Evening FLW,
Maybe not so concise  . . .but here's a word or two about pins vs. rollers 
Short story: The difference between pin and roller is in what types of reactions you can expect at the connections between a beam and its support. . .
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PINS
Simple supports produce an end condition we refer to as a "pinned end" ~ also known as hinged or unrestrained.
Simply put: this is a situation where the end of the supported member is free to rotate when a load is applied to it.
As it relates to the forces acting at that joint, reactions at simple supports would be as follows: H > 0, V > 0, & M = 0 (You can expect to deal with the horizontally and vertically acting forces, but you can't develop moments)
True pins are found in bridge construction (literally a 4" to 6" diamater pin supported in a steel saddle at a bridge abutment) they are rare in building construction.
Even so, we refer to several common situations as pinned connections. Two examples: (1) a simply supported beam bearing on a masonry wall. (2) a steel beam connected by clip angle to a steel column.
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ROLLERS
Roller supports are similar to simple supports, but in this case the supported member can roll / is allowed to move in the horizontal direction.
Again, these connections work like champions in bridge construction, where thermal expansion is a very real and very big design concern.
As it relates to the forces acting at that joint, reactions at roller supports would be as follows: H = 0, V > 0, & M = 0 (A roller offers no resistance in the horizontal direction & can't develop moments, but it can provide a vertical reaction)
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FrankLloydWrong
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| Joined: | Mon Jun 30th, 2008 |
| Location: | Chicago |
| Posts: | 8 |
| Exams Taken: | PD, GS, LF, ME, BD/MM, CD, SP, BP, BT | | Exams Passed: | PD, GS, LF, ME, BD/MM, CD, BP | | Describes Me: | one dimensional |
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Posted: Fri Aug 8th, 2008 05:25 am |
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| Thanks, dude. Much obliged.
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Current time is 12:54 pm | |
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