The time diagrams can be defined as tabulated values of time steps, as periodic defining of the excitation frequency and shift, or using a function term. In all cases, the multiplier k is defined. This is multiplied by the static load of the assigned load case.
Connecting Static Load Cases with Time Diagrams for Time History Analysis
The stiffness of gas given by the ideal gas law pV = nRT can be considered in the nonlinear dynamic analysis.
The calculation of gas is available for accelerograms and time diagrams for both the explicit analysis and the nonlinear implicit Newmark analysis. To determine the gas behavior correctly, at least two FE layers for gas solids should be defined.
Calculation with consideration of a damping ratio (or Lehr's damping) is not possible in the direct time step integrations. Instead, the Rayleigh damping coefficients must be specified by the user.
In technical literature, the given damping ratio for specific construction forms is, in many cases, only a rough approximation of the real damping ratios. In RF-/DYNAM Pro - Forced Vibrations, it is possible to use the value of the damping ratio to determine the Rayleigh damping. This may occur at one or two natural angular frequencies defined by the user.
The member type 'Dashpot' can be used for time history analyzes in RFEM/RSTAB with the add-on modules RF-/DYNAM Pro - Forced Vibrations and RF-/DYNAM Pro - Nonlinear Time History. This linear viscous damping element considers forces dependent on velocity.
With regard to viscoelasticity, the member type 'Dashpot' is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).
- Response spectra of numerous standards (ASCE 7-16, NBC 2015, etc.)
- User-defined response spectra or those generated from accelerograms
- Direction-relative response spectrum approach
- Manual or automatic selection of the relevant mode shapes of response spectra (5% rule of EC 8 applicable)
- Result combinations by modal superimposition (SRSS or CQC rule) and by direction superimposition (SRSS or 100% / 30% rule)