Calculation

Load-dependent rotational rigidity

In XFrame2d a geometric nonlinear analysis (GNL) is calculated as standard. The force distribution is determined iteratively. The beam-column moment connections can be entered. The rotational stiffness of all connections per iteration step is determined. On the basis of the occurring moment in the beam connection, the rotational rigidity diagram of the designed connection (see diagram below) determines a rotational stiffness or spring stiffness which is then used in the next iteration step. The iteration stops when there are no more changes in the distribution of forces.

In XFrame2d, a load-dependent rotational rigidity is therefore taken into account for all moment connections. This of course gives the most accurate result and leads to an economically optimal design.

At small moments (under 2/3 Mj, Rd), initial rotational stiffness Sj, ini is calculated. At larger moments with the rotational stiffness Sj corresponding to the bending moment Mj, Ed. The trilinear rotational rigidity diagram is used. See the diagram below.

XFrame2d