Solver Type
There are two Solver types available in RSSeismic:
- Lumped Mass
- Finite elements
Depending on the solution type selected, different project options are available.
| Solver type | Analysis Method | Solution Type | Soil Model | Hysteretic Re/Un-loading Formulation | Pore Pressure Options |
| Lumped Mass | Linear | Frequency and Time domain | - | - | - |
| Equivalent Linear | Frequency domain |
|
| - | |
| Nonlinear | Time domain |
| |||
| Finite elements | Linear | Time domain |
| - | - |
| Nonlinear | Time domain |
|
|
|
Lumped Mass Method
The lumped mass method implemented in RSSeismic discretizes the soil column into a series of horizontal layers, each represented by a concentrated mass located at the layer boundaries. Adjacent masses are connected by nonlinear springs and dashpots that represent the shear stiffness and damping of the intervening soil layer. The equations of motion are solved in the time domain using an explicit integration scheme, allowing the stiffness and damping of each layer to evolve according to the selected constitutive model.
Finite Elements Method
The finite element method implemented in RSSeismic discretizes the soil column into a stack of eight-node hexahedral elements with tied-node constraints at each depth level to enforce one-dimensional site-response behavior within a three-dimensional formulation. A diagonal lumped mass matrix is used, and the equations of motion are solved in the time domain using the explicit central-difference method. The engine supports both rigid-base and elastic base boundary conditions. Undrained and partially drained conditions are handled through effective stress pore pressure coupling , specifically the Biot u-p formulation, that solves for excess pore-pressure generation and vertical dissipation alongside the mechanical response.