Answer:
RFEM and RSTAB interpolate the variable stiffnesses along the member by higher-order polynomials. The internal determination of tapered cross-sections is done using the taper shape (see Image 01). If different cross-sections are defined for the member start and end, you can select the "linear" or "quadratic" taper shape. This way, it is possible to represent the taper geometry for the determination of the interpolated cross-section properties.
In most cases, the layout of the taper is linear; that is, the member only tapers and extends regularly over the depth of the start to the end section. However, if the cross-section width and depth change, the quadratic shape is recommended for the interpolation of the cross-section properties.
For more precise results, it can also be reasonable to divide the tapered member and create additional cross-sections.
The calculation of tapered members is also influenced by the division for tapered and foundation members, which is managed in the calculation parameters (see Image 02).
