Glossary Term

A taper is a member or a surface with a variable statical moments and warping statical moment of a cross-sections.

Application cases for variable cross-section shapes are the reinforcements in the area of frame joints, cantilevered members or slabs and towers with conical hollow sections.

Modelling in RFEM/RSTAB

A tapered member is modelled by defining different cross-sections for the member start and the member end. The cross-section type must be consistent, for example, I-shaped cross-sections at both member ends. To determine the member stiffness, the cross-section properties are interpolated using the member length. The interpolation can be adapted to the geometry of the taper: as a rule of linear distribution, the cross-section is only reduced or extended by the height. If the cross-section width is also changed, it is recommended to use the quadratic approach for the interpolation of the cross-section properties.

It is also possible to model surfaces as tapers by defining the surface thickness by three points as linearly variable. The definition points can be within the surface or even outside it as long as they rest in the plane of the surface.


You can design tapered members in the add‑on modules, such as RF‑/STEEL or RF‑/STEEL EC3, if there is a uniform number of stress points.

Under the links below, you can find the application examples for designs of a tapered member in the add‑on modules.


Taper Tapered member Variable cross-section Moment of inertia Member stiffness Stress point



RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

Price of First License
3,540.00 USD
RSTAB Main Program
RSTAB 8.xx

Main Program

The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

Price of First License
2,550.00 USD