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[Civil]Discontinuous Shear Force Diagrams in the Analysis Results of Tapered Sections

Question

I'm getting discontinuous shear forces in the analysis results of tapered sections.

 

Answer

When you offset the tapered section, if the offset of the transition section (tapered part) is applied to the upper (Center-Top) or lower (Center-Bottom) part, it causes the neutral axis to twist, resulting in discontinuous shear forces.

 

Let's examine an example

In the example, the red box represents the tapered section (transition section) offset to Center-Top, while the other parts are normal sections offset to Center-Center.

In this case, when you check the shear force distribution, you will notice discontinuities in the tapered section, as shown in your diagram.

To address this issue, you can use the [Change Local Axis of Tapered Section for Force/stress Calculation]  in midas Civil.

midas Civil provides the ability to calculate member forces considering the inclined direction of the centroid when defining tapered sections.

You can do this by checking [Change Local Axis of Tapered Section for Force/stress Calculation] in the Analysis tab > Main Control group > Main Control Data.

This function allows the user to examine the member forces and stresses by changing the element coordinate system parallel to the offset line when a cross-sectional offset is applied to the top or bottom of the section, as shown in the image below.

This option can be useful when the user wants to get the result of the vertical member force parallel to the gravity direction of the section.

 

The image below shows the result of checking [Change Local Axis of Tapered Section for Force/stress Calculation] and requesting the result of the vertical member force parallel to the gravity direction of the section. The shear force diagram of the upper slab, which was previously represented as discontinuous, has been corrected so that the normal member forces and stresses can be examined.

 

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