- #1
rmrramani
- 17
- 0
can u explain what is kinematic indeterminancy?
What is kinematic indeterminancy?
- Thread starter rmrramani
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- Kinematic
In summary, kinematic indeterminacy is a structural engineering term that refers to a situation where the forces in a structure cannot be determined solely from the equations of equilibrium. This is different from static indeterminacy, where the forces can still be calculated. Kinematic indeterminacy occurs when there are not enough equilibrium equations to uniquely determine the forces, and the structure can change shape in response to a load.
- #2
Cyrus
- 3,238
- 16
I have never even heard this term, but I would be interested to know the context in which you heard it.
- #3
rmrramani
- 17
- 0
its similar to static indeterminancy,i red in (that word only i got)TH.megson(structural and stress analysis)
- #4
Studiot
- 5,440
- 9
It's a structural engineering term.
Look at the attached sketches.
(1) This situation is called Statically Determinate.
Shows a simple pin jointed truss with 5 members.
It is supported at A and B and loaded in some way at D
It is also restrained from sideways movement at A, or load L would just push it sideways.
This is a structure because it does not change shape in response to load L. It remains a rectangle with one diagonal.
Since there are just enough equilibrium equations (horizontal, vertical and moments) we can completely determined the forces in the members, given L and the dimensions.
(2) This situation is called Statically Indeterminate.
Shows the same thing with one extra diagonal member added.
A little calculation will show that we no longer have enough equations to uniquely determine the member forces, although the reactions will not have changed.
(3) This situation is called Kinematically Indeterminate.
The same rectangle, but we have taken away both diagonals. This is no longer a structure it is now a mechanism because it can (and will) change shape to a parallelogram in response to load L.
Although it remains fixed at A and B, it is not possible to determine how far the rectangle collapse from the equations of equilibrium alone. So the situation is indeterminate and the member forces cannot be calculated from equilibrium.
Look at the attached sketches.
(1) This situation is called Statically Determinate.
Shows a simple pin jointed truss with 5 members.
It is supported at A and B and loaded in some way at D
It is also restrained from sideways movement at A, or load L would just push it sideways.
This is a structure because it does not change shape in response to load L. It remains a rectangle with one diagonal.
Since there are just enough equilibrium equations (horizontal, vertical and moments) we can completely determined the forces in the members, given L and the dimensions.
(2) This situation is called Statically Indeterminate.
Shows the same thing with one extra diagonal member added.
A little calculation will show that we no longer have enough equations to uniquely determine the member forces, although the reactions will not have changed.
(3) This situation is called Kinematically Indeterminate.
The same rectangle, but we have taken away both diagonals. This is no longer a structure it is now a mechanism because it can (and will) change shape to a parallelogram in response to load L.
Although it remains fixed at A and B, it is not possible to determine how far the rectangle collapse from the equations of equilibrium alone. So the situation is indeterminate and the member forces cannot be calculated from equilibrium.
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- #5
Cyrus
- 3,238
- 16
Studiot, thank you for this reply. It is both concise and precise.
Related to What is kinematic indeterminancy?
What is kinematic indeterminacy?
Kinematic indeterminacy refers to a structural system where the number of unknown displacements exceeds the number of available equations of equilibrium. This means that the system cannot be solved using basic structural analysis methods and requires additional techniques.
Why is kinematic indeterminacy important?
Kinematic indeterminacy is important because it affects the stability and safety of a structure. If a structure is kinematically indeterminate, it is more susceptible to failure and collapse due to the inability to accurately predict its behavior under different loading conditions.
How do you determine the degree of kinematic indeterminacy in a structure?
The degree of kinematic indeterminacy can be determined by using the equation i = 3m - r, where i is the degree of indeterminacy, m is the number of members, and r is the number of support reactions. This equation is based on the principles of statics and is applicable to both 2D and 3D structures.
What are some methods for solving kinematically indeterminate structures?
There are several methods for solving kinematically indeterminate structures, including the force method, the displacement method, and the stiffness method. These methods use different approaches to solve the additional unknowns in the structure and determine the internal forces and deformations of the structure.
What are some real-life examples of kinematically indeterminate structures?
Some real-life examples of kinematically indeterminate structures include bridges, high-rise buildings, and large industrial structures. These structures are designed to withstand various loading conditions and require advanced analysis techniques to accurately predict their behavior and ensure their safety and stability.
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