Neglecting axial deformation is slope deflection method

[Sadeq]

Hello,

When we use slope deflection method in frames we neglect axial deformation in order to get the same delta when the frame is sway,(that what i understood)

So i have two questions
1. Neglecting axial deformation means ignoring axial force??Or what??
2. How to neglect axial deformation in frame matrix like picture?if we use ,matrix not slope deflection

 

[pongo38]

A general assumption made in most structural analyses is that there is no significant change of geometry from before loading to after loading. In many situations, if flexural displacements are small, then axial displacements can be regarded as vanishingly small. Exceptions that come to mind include triangulated frames with loads at the nodes only, and cable-supported structures where cable extension can be significant. It could be instructive for you to use your matrix with all the 'AE/L' terms included, and compare the result with when they are all excluded.

 

[Sadeq]

Thank you very much brother.
I understand what you said
but regarding to first question. does Neglecting axial deformation means ignoring axial force??Or what??
and you say if i exlcuded EA/L from the above matrix, i should get result as slope deflection for the same problem.right

 

[Sadeq]

UP

some help please

 

[rezeew]

method

Thank you for your questions. Neglecting axial deformation in the slope deflection method means that we are assuming that the axial force in the frame members is negligible compared to the bending moments. This assumption is made in order to simplify the analysis and to get a reasonable approximation of the actual behavior of the frame. However, it should be noted that this assumption is not always accurate and can lead to errors in the analysis results.

To neglect axial deformation in the frame matrix, we can use a similar approach as in the slope deflection method. We can assume that the axial forces in the frame members are negligible and only consider the bending moments. This can be represented in the frame matrix by setting the axial force terms to zero and only solving for the bending moment terms. Again, this approach may not always be accurate and should be used with caution.

In conclusion, neglecting axial deformation in the slope deflection method and in the frame matrix is a simplification that is made in order to make the analysis more manageable. However, it is important to keep in mind that this assumption may not always be accurate and can lead to errors in the analysis results. It is always recommended to consider the effects of axial deformation in more complex and accurate analyses.