ANALYS Module Options

The ANALYS module is the heart of the ACS SASSI code. This module solves the dynamic problem. This module also controls the restart modes of the ACS SASSI system. ACS SASSI ANALYS has four different running modes - the first mode is the initiation mode and the other three are the restart modes.

Mode 1 - Initiation: This is the first mode to be executed for a new problem. In this mode, ACS SASSI ANALYS basically reads the three input files - File 1 (or File 9), File 3, and File 4 - and generates the output files - File 5, File 6, and File 8, which contain the impedance matrices of the interaction nodes, the reduced modified stiffnesses of the total system, and the acceleration (or displacement) transfer functions relative to the control motion (input dynamic force), respectively, computed for the specified frequencies which must reside on the input files.

It should be noted that the control motion defined by the user in the Analysis Options - SITE dialog box for seismic problems is in the x’y’z’ coordinate system as defined by the ACS SASSI SITE module and must be transformed to the global structural coordinate system xyz in module ANALYS. Therefore, the user must enter the angle between the two coordinate systems and the location of the control point on the horizontal plane.

Mode 2 - New Structure: If the physical properties of the structure(s) are changed or the geometry of the structure is altered, then, as long as other data remain intact, module ANALYS may be restarted using Mode 2.

In order to use this mode, a new File 4 has to be generated by re-executing module HOUSE. Since the geometry and numbering of the nodal points below the ground have not changed, the impedance matrices can be recovered. The information on the two input files is then used to compute the new reduced modified stiffness of the structure. File 1 (or File 9) is also an input file, so that the new transfer functions of the response can be computed and then saved in a new File 8.

Mode 3 - New Seismic Environment: If the seismic environment is changed, the information from File 1 changes while that from File 5 and File 6 remain intact. Therefore, module ANALYS could be restarted in Mode 3 with the new File 1 and old File 5 ad File 6 as input. The results are saved in a new File 8.

Mode 4 - New Dynamic Loading: If the problem is to be analyzed for a new set of external forces, then the program module ANALYS can be restarted in Mode4. This mode is similar to Mode 3, except that it is used for foundation vibration rather than seismic problems. Therefore, File 5 is not required as input. Only File 6 and a new File 9 are needed for this restart analysis. The results are also saved in the new File 8.

ANALYS Options Window

The following options allow you to specify the analysis options for ACS SASSI ANALYS module:

Frequency Numbers

Set the Take Frequency Numbers from File1 / File9 check box if you wish to load the frequencies from File 1 or File 9. Otherwise, type the frequency set number in the Frequency Set Number edit box. The value is the same as set in Analysis Options - SITE dialog box.

Frequencies for which a complete solution is desired must be specified at this stage. The program automatically surveys these frequencies to make sure that they reside in the input files. If one or more frequencies are not found on the input files, ANALYS stops. It is also possible to break the complete frequency set into smaller sets and then run each set separately. The results of these separate runs can be combined into the complete solution. This has the advantage that the runs are smaller and the created files occupy smaller memory space during the execution.

You may specify a new frequency set number to solve the problem for new frequencies and combine the results with those of old frequencies if the analysis demands it at a later time.

Since more than 90% of the execution time of all ACS SASSI modules is spent by the ANALYS module, assessment of the final time of the run job can be made in advance by estimating the time of solving one single frequency and multiplying it by the number of frequencies for which a solution is desired.

Coordinate systems in module SITE and HOUSE

The ANALYS results are the computed complex transfer functions in degrees of freedom of the SSI model that are saved on FILE8. This FILE8 is used by MOTION and STRESS modules to compute the real SSI response at selected nodes and elements.

A new capability that is specific to the seismic incoherent SSI analysis is included in this version by the new PINT module (“Polishing” INTeraction results). PINT has to be run after ANALYS. Using the PINT module, the computed incoherent transfer functions (ITF) could be smoothed to improve the accuracy of SSI analysis results. The PINT module has as the input, FILE8, and as the output, FILE80. If the analyst wants to use smoothed ITF to get the final SSI results, then he is required to rename FILE80 as FILE8 before running MOTION and STRESS modules. In addition to FILE8, the PINT module needs a text file input called “smooth.par” that contains on the first line the smoothing input parameter. This smoothing parameter is defined by an integer value in columns 5 to 10 (alignment to the right, column 10).

It should be noted that the input value of the smoothing input parameter has to be selected on a case-by-case basis. Because of this, for appropriate selection of the smoothing input parameter value, we highly recommend in the beginning of using this option to contact us by email at acs.sassi@ghiocel-tech.com. It is important to contact us since the ITF smoothing is a new concept for improving incoherent SSI analysis results that is not well-documented yet in technical literature. As an alternate to the use of the ITF smoothing, the analyst could use the stochastic simulation option in ANALYS and compute average SSI results for an ensemble of realizations.