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Useful Program Features
The Knowledge Base includes technical articles on a wide array of structural analysis and design topics.
These articles are intended to help you navigate through the Dlubal programs, learn efficient tips and tricks, and provide further insight to the program features.
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DIN EN 1998-1 with the National Annex DIN EN 1998-1/NA specifies how to determine seismic loads. The standard applies to structural engineering in seismic areas.
There can be numerous nonlinearities in a structural system. In order to model them realistically in a dynamic analysis, the RF-DYNAM Pro - Nonlinear Time Histoey add-on module was developed. To explain how the add-on module works, the procedure is described below with an example.
The story drift of a building provides valuable information about its structural behavior under seismic loads.
Consideration of P-Delta Effects (Second-Order Analysis) in the Response Spectrum Analysis According to ASCE 7-16RFEM offers the option to perform a response spectrum analysis according to ASCE 7-16. This standard describes the determination of seismic loads for the US-American market. It might happen that the so-called P-Delta effect has to be considered due to the stiffness of the entire structure to be able to calculate the internal forces and carry out the design.
In RF-/DYNAM Pro - Equivalent Loads, the equivalent seismic loads can be calculated according to different standards. By calculating the equivalent loads for each eigenvalue, it is not directly possible to obtain the transversal shear for each story to perform an analysis afterwards. The following example describes the option to calculate the transversal shear quickly and efficiently.
In a multi-modal response spectrum analysis, it is important to determine a sufficient number of eigenvalues of the structure and to consider their dynamic responses. Regulations such as EN 1998-1  and other international standards require to activate 90 % of the structural mass. This means: to determine as many eigenvalues that the sum of the effective modal mass factor is greater 0.9.
The Time Course Monitor displays results of a time history analysis from RF‑/DYNAM Pro - Forced Vibrations. The graphic can be adjusted in the settings. This can be reached via the right click in the context menu. For example you can activate or deactivate the grid in the graphic. Those changes are overtaken into the printout report when you print the graphic.
In RF-/DYNAM Pro - Equivalent Loads, a signed result option in accordance to the dominant eigenmode is available since version X.06.3039. For the modal combination of results corresponding to the single eigenvalues a quadratic combination rule has to be used, in RFEM and RSTAB the SRSS and the CQC rule are available. It is only allowed to combine results not loads directly. The reason are the mode shapes which are arbitrarily scaled and signed.
For the ultimate limit state design, EN 1998‑1 , Section 2.2.2 and 22.214.171.124, require the calculation considering the second‑order theory (P‑Δ effect). This effect need not be taken into account only if the interstorey drift sensitivity coefficient θ is less than 0.1.
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