The discussion revolves around identifying whether members of a simple truss are in tension or compression without performing calculations. Participants explore methods of visual inspection and practical examples to illustrate their points, focusing on both simple and more complex truss structures.
Participants generally agree that visual inspection can be useful for simple truss problems, but there is no consensus on the effectiveness of this method for more complex structures. Multiple views on the necessity of calculations for complicated trusses remain present.
Limitations include the dependence on the simplicity of the truss structure for visual identification of forces and the unresolved nature of how to approach more complex configurations without calculations.
I'm sorry I can't get what you mean. How does the compressive member come?PhanthomJay said:You can't always tell by inspection, but in this simple case, does the leg on the right get pushed down or pulled up when the load is applied as shown? How about what happens to the other leg?
Compressive forces are 'pushing' forces and tensile forces are 'pulling' forces. Take 2 popsicle sticks and fasten them at one end in the shape of the upside down V as in your problem ( ^ ). Set the legs on a table and apply the rightward horizontal force at the top. One of the legs will pull off the table, while the other leg will push on the table. Which is which? The one that pulls would be in tension if anchored to the table, and the one that pushes will be in compression.Dave1357 said:I'm sorry I can't get what you mean. How does the compressive member come?
Oh, I understand. Thanks a lot !PhanthomJay said:Compressive forces are 'pushing' forces and tensile forces are 'pulling' forces. Take 2 popsicle sticks and fasten them at one end in the shape of the upside down V as in your problem ( ^ ). Set the legs on a table and apply the rightward horizontal force at the top. One of the legs will pull off the table, while the other leg will push on the table. Which is which? The one that pulls would be in tension if anchored to the table, and the one that pushes will be in compression.
They can be a bit more complex, but, yes, that is best. Try to visualize when you can, then run the numbers.Dave1357 said:Oh, I understand. Thanks a lot !
So, this kind of checking can only be applied on simple case like the above, right?
If there are complicated trusses, we must use method of joint/section to calculate.