RF-LOAD-HISTORY | Input of Load Steps

This article describes and explains the influence of bending stiffness of cables on their internal forces. Furthermore, the text provides information on how this influence can be reduced.

The ASCE 7-22 Standard [1], Sect. 12.9.1.6 specifies when P-delta effects should be considered when running a modal response spectrum analysis for seismic design. In the NBC 2020 [2], Sent. 4.1.8.3.8.c gives only a short requirement that sway effects due to the interaction of gravity loads with the deformed structure should be considered. Therefore, there may be situations where second-order effects, also known as P-delta, must be considered when carrying out a seismic analysis.

This article presents the basic concepts in structural dynamics and their role in the seismic design of structures. Great emphasis is given to explaining the technical aspects in an understandable way, so that readers without deep technical knowledge can gain an insight into the subject.

The calculation is performed successively for each load step. Permanent (plastic) deformations of previous load steps are considered when calculating further load steps. This way, it is also possible to perform a calculation with a structure relief.

The loads of the individual steps are added up (depending on the signs) throughout the calculation process. You can freely select the method of analysis (linear static, second-order, large deformation, and postcritical analysis). Furthermore, the module manages the global calculation settings.

After defining the entire model and loading in RFEM, it is possible to enter load steps and descriptions in the 1.1 General Data window.

In Window 1.2 Loads, you can assign the load cases or load combinations to the different load increments. It is possible to multiply them by a load factor.

• Simple definition of load increments
• Simple assignment of load cases and load combinations to load increments
• Consideration of plastic deformations (isotropic hardening behavior) of previous load increments
• Numerical and graphical display of results (deformations, support forces, internal forces, stresses, strains, and so on) for individual load increments
• Detailed printout report including result documentation for all load increments