Analysis Method

There are three Analysis method options available in RSSeismic:

• Linear
• Equivalent linear
• Nonlinear

Depending on the analysis method selected, different project options are available:

Analysis Method	Solution Type	Soil Model	Hysteretic Re/Un-loading Formulation	Pore Pressure Options
Linear	Frequency and Time Domain	-	-	-
Equivalent Linear	Frequency domain	General Quadratic/Hyperbolic Model (GQ/H) Pressure-Dependent Modified Kondner Zelasko (MKZ) Yee et al. (2013) Linear Discrete Points (Equivalent Linear)	Non-Masing Masing	-
Nonlinear	Time domain			Generate Excess Porewater Pressure Enable Dissipation Make top of Profile Permeable Make Bottom of Profile Perm

Linear

A Linear Analysis model can be solved in the following two ways:

• Frequency Domain
• Time Domain

In both linear site response analyses, the maximum soil stiffness and a constant damping ratio are considered throughout the entire time history

Equivalent Linear

The Equivalent Linear model employs an iterative procedure in the selection of the shear modulus and damping ratio soil properties (as pioneered in program SHAKE). These properties can be defined by discrete points or by defining the soil parameters that define the backbone curve of one of the nonlinear models.

The option of defining the soil curves using discrete points is only applicable for the Equivalent Linear analysis. For this option, the G/G_max and damping ratio (%) are defined as functions of shear strain (%).

Nonlinear

Non-linear analysis solves the equations of motions in time domain using the Newmark β method (implicit) or the Heun’s Method (explicit). Several soil models are available for users to select from (summarized in the above table). The analysis can be performed with or without pore water pressure generation.

The user has the option of obtaining the site response results using the equivalent linear method automatically whenever nonlinear site response analysis is conducted. It is highly recommended that Equivalent Linear results are always examined whenever a Nonlinear analysis is conducted. This can be done by using the Complementary analyses option and turning on Equivalent Linear – Frequency Domain.

Pore pressure options

When performing a nonlinear analysis, users also have the options to:

• Generate excess pore water pressure
  
  • Enable dissipation
    • Make top of profile permeable
    • Make bottom of profile permeable
      

For more details, see the Pore Water Pressure Generation and Dissipation topic.