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• ### Is it also possible to use nonlinear material behavior in the time history analysis?

To consider nonlinearities in Dynamics, you need the addition of a Nonlinear Time History Method in RFEM / RSTAB. This addition is different in RSTAB and RFEM by the type of nonlinearities to be applied.

RSTAB nonlinear time history method:

Nonlinear member types such as tension and compression members as well as cables

Member nonlinearities such as failure, tearing, and creeping under tension or compression

Supports nonlinearities such as failure, friction, diagram, and partial action

Nonlinearities of hinges such as friction, partial action, diagram and fast in case of positive or negative internal forces

RFEM Nonlinear Time-Course Process

in addition, you can work with nonlinear material behavior

• ### I create a picture for the time in DYNAM PRO, and paste it via the clipboard in the printout report, this picture appears very blurred. What can I do about it?

In this case, you have the option to print the image in the timeline diagram directly into the printout report. Here you proceed as described in the picture.
• ### With the additional module "RF- / DYNAM Pro" there are the parameters modal mass, participation factor and substitute mass. The manual contains the formulas, the meaning and the explanation, as well as usage would be just as helpful.

Modal mass

Each multi-mass system can usually be represented by a single-mass system. When you do this transformation, you need the modal mass of the system. This mass is needed to generate the frequency of the equivalent single-frequency oscillator.

Beiteilungsfaktor

This factor can also be negative because it is composed of the substitute mass at a node and the associated displacement due to the eigenform. If the deflection is in the negative direction, the participation factor becomes negative. The replacement mass factor is then still positive, since the participation factor is squared. (see formula)

equivalent mass

The equivalent mass of a system is a part of the total mass which is excited due to the vibration of the multi-mass oscillator. The equivalent mass of a system can be between zero and the total mass. The replacement mass factor is only the quotient of the total mass to the substitute mass. As a rule, this makes it possible to check more quickly what proportion of the excited mass of the respective eigenform is. Should it happen that the substitute mass factor is greater than 1, one should check the discretization of the system and, if necessary, refine the division of the nodes or the FE mesh.

For an earth analysis, the substitute mass factor and the substitute mass are usually decisive, since these values are used to calculate the dynamic equivalent loads on the building.
• ### Which time step should I choose for calculating the time history method in the module RF- / DYNAM Pro?

There are two options to choose from: an automatic time step selection and a manual one. Especially for a structure with nonlinearities, it is always recommended to manually select the time step and perform a time step convergence study that compares the computation time and accuracy.

The time step to choose depends on many factors, including the excitation frequency, the frequency and size of the structure, and the degree of non-linearity. So no general statement about the size of the time step can be made.

For detailed information on this and many other topics, see the <a href="https://www.dlubal.com/-media/3BEF143083FA4DC3A9463B0E4166CCF0.ashx" target="_blank"> manual </a> of the additional module RF- / DYNAM Pro.

• ### After using the DYNAM Pro module, I get the following warning during the calculation: 'Incorrect addition of load cases in the result combination!' What does it mean?

The message about the incorrect addition of load cases should be considered as an indication: It appears when a nonlinear structure (for example, including tension members) is superimposed in a RC.

Eventually, there can be a different structural system for each load case as different members are effective. In DYNAM Pro, your system is linearized when using the response spectrum analysis. Therefore, this message is always displayed when nonlinear elements exist in the model.