This module enables Time History as well as Harmonic analyses. Time history analysis can be used for example to simulate harmonic loads, explosions, impacts, etc. Harmonic load calculation can be required to check vibrations due to machinery, to verify structural integrity of a floor loaded by an aerobics class, to check the response of a building near a railroad or major traffic lane etc.
With Harmonic analysis the structure will be loaded with one or more sinusoidal nodal loads of given amplitude and frequency, which will cause the structure to vibrate.
- User input nodal loads of given intensities and associate them to one or more load cases. Each load case is characterized by a frequency and overall damping value. More than one harmonic load case can be input, each with a different value of frequency and/or damping.
- After linear calculation, the results may than available in the same way as results of a standard static calculation (The same menus as for static load cases are available to view numerical or graphical results: displacements, internal forces, and reactions)
TIME HISTORY ANALYSIS
With Time History analysis, the user has firstly to input one or more dynamic functions which specify the nodal loads as function of the time. Then, two computational methods are available to solve the numerical problem:
- Direct time integration: this is the common approach found in literature, where the equilibrium of the structure is explicitly computed in each time step
- Modal superposition with time integration: this approach uses a modal decomposition of the structural behaviour; it allows filtering out unwanted high-frequency peaks in the response of the structure and is less computationally intensive than the direct approach
Finally, the results time histories (internal forces, stress, displacements, reactions) are available for each computed time step.