Earthquake
The program allows for addressing the impact of seismic actions on a geotechnical structure. The earthquake analysis can be executed in an arbitrary construction stage.
The earthquake loading is defined by an accelerogram which can be either generated by the program, imported or entered by points. The accelerogram is generated so that its response spectrum corresponds to the chosen elastic response spectrum defined in design codes.
Either fixed or absorbing boundary conditions can be specified on the bottom boundary. So-called free-field boundary conditions are defined on the lateral boundaries to correctly represent the deviation from the Free field column analysis.
The earthquake analysis includes the solution of the eigenvalue problem to provide the natural frequencies and corresponding mode shapes. The natural frequencies are needed in setting the parameters of Rayleigh damping. The results of the eigenvalue analysis include modal participation factors and modal effective mass.
To allow for running the earthquake analysis, check "Allow earthquake analysis" in the Topology regime, the frame "Settings".
With this option checked:
- The "Soil properties" dialogue window introduces new parameters pertinent to dynamic analysis including damping;
- The "Earthquake" frame then appears in each construction stage to allow for entering the seismic load (accelerogram) and specific boundary conditions.
The dynamic analysis outputs the mechanical quantities - displacements, stresses, strains, internal forces, etc. - in every time step.
The earthquake analysis has the following limitations:
- it is not possible to run it in the "Axial symmetry" analysis mode;
- the critical state constitutive models do not adopt "the dynamic modulus";
- the analysis is not allowed when "rigid bodies" are placed on the lateral boundaries of the numerical model.
Further details are available in the theoretical manual on our website.