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REVISION 3Incoherent Analysis

1) Please follow the Installation-Networkto install the program package on the stand-alone PC or on the networked set of PCs. The USB hard key works either as stand-alone or on the network system.

2) SASSI2000, Rev 3 offers all features of the Rev 2 plus the additional capability forincoherent analysis and offers a new element, thick plate element that can provideforces in out of plane direction for design.

3) For conventional coherent analysis, please follow the same sequence of runs as forRev 2. There is no change in input data. Previously generated data for Version 2can be used for Version 3.

4) The incoherent analysis is based on the superposition of spatial modes in theground. Please read the document called SASSI Incoh-Formulation s in the folderwith the theoretical manual. For each frequency SSI problem is solved each spatialmode. Except for the first spatial model, all other modes use re-start mode 3 optionin ANALYS. The transfer function results from all spatial modes are combined usingthe SRSS method. The document, SASSI Incoh-Formulation, provides theformulation of the method and results of several verification examples for the methodusing the theoretical model by Luco et al.

5) The CD under the folder EXAMPLES/EPRI contained two EPRI reports. One reportdescribes the basis of the ground motion incoherency model. The model identifiedas hard rock model has been approvedby the US NRC for nuclear power plantanalysis and design. The other models are for general use and have not beenapproved by the US NRC. The second EPRI report describes the details ofverification of incoherency model for SSI analysis. A multi-stick model is used and

the results of SASSI methods are compared with CLASSI methods. Appendix A ofthe report shows the results of all methods due one direction of shaking at a time. InChapter 5, the results of various methods are also compared. The results inChapter 5 do include the co-directional effects and show the total response for eachdirection identified. Among the methods presented, only SASSI-SRSS, CLASSI-SRSS and SASSI simulation have been approvedby the US NRC.

6) Typically, solutions of 5 to 10 spatial modes are sufficient for the very stiff nuclear

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power plant foundations. The user may choose to combine fewer modes or ask formore than 10 modes for parametric study.

7) The sequence of runs for incoherent analysis consists of SITE, POINT3, HOUSE,INCOH, ANALYS and MOTION. The program INCOH provides several models for

incoherent analysis. The hard rock model by N Abrahamson has been approved byUS NRC for application to nuclear structures. The model by Luco is a theoreticalmodel that is useful to develop SSI solution for comparison with Lucos theoreticalSSI solutions published in technical papers.

8) In addition to INCOH, there is a new program module COMBINI that combines thesolution of all spatial modes selected by the user using SRSS to get the final solutionfor each frequency of analysis. The previous module COMBIN is kept and is used tocombine the solution from multiple sets of frequencies.

9) Except for module INCOH that requires a new input file, there is no change in the

data for all other modules except for ANALYS. There is one new entry in ANALYSdata that user needs to ask for the incoherent analysis by inserting number 1 asdescribed in the user manual in 2ndline column 30.

10) Incoherent analysis is only performed for 3D problems and is not applicable to 2Dproblems due to unsymmetrical rocking and torsional motion.

11) The results of incoherent analysis (tape 8) are used by MOTION to compute allresponses in terms of acceleration response spectra and maximum accelerations.Computation of forces by STRESS is limited to coherent analysis and cannot beused by incoherent results. This is because incoherency is a high frequency effect(say above 10 Hz) and does not impact low frequency force responses.

12) As an example, the input/output files for the example used by the EPRI study isprovided under the folder EPRI. This example is fully described in the EPRI reportenclosed on the CD. Under folder C:\SASSI2000_Rev3\EXAMPLES\EPRI-Final-Report-Example-AP1000\INPUT-OUTPUT-RUN the word files of the resultscomparing SASSI-SRSS solution to other SSI solution due to X-, Y- and Z-shakingare provided. The same figures do exist in Appendix A of the EPRI report.

13) The EPRI problem is analyzed with two sets of frequencies, set a and set b. Go toC:\SASSI2000_Rev3\EXAMPLES\EPRI-Final-Report-Example-AP1000\INPUT-OUTPUT-RUN\Freq-Seta and click on 1-EPRI.bat. This will perform the analysis forthe first set f frequencies and perform SRSS on the 10 spatial modes for eachfrequency of analysis. 1-EPRI.bat calls the other two .bat files to complete theSRSS calculation. Next go to C:\SASSI2000_Rev3\EXAMPLES\EPRI-Final-Report-Example-AP1000\INPUT-OUTPUT-RUN\Freq-Setb and click on 1-EPRI.bat to getthe solution for set b. Finally, go to C:\SASSI2000_Rev3\EXAMPLES\EPRI-Final-Report-Example-AP1000\INPUT-OUTPUT-RUN\Response-ARS and click onResponse.bat. These sets of runs combine the results for two sets of frequenciesand runs MOTION. The results are saved in terms of MOTION outputs and tapes

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16.

14) Please note the EPRI report and comparison of SASSI and CLASSI is based on theN Abrahamson soil model and not the hard rock model. The soil model provides

more incoherency and was considered to be a better model for the purpose ofComparing various SSI methods.

15) As described in the EPRI, due to unsymmetric rocking and torsional vibration onceincoherency is used, and for the purpose of comparison with CLASSI, the couplingresponses at the edge of the foundation are obtained by multiplying the rotationacceleration response spectra by the arm. This approach is used by CLASSI forfoundation. The SASSI results are processed similarly.

16) For computers with multi core capability, each CPU can be directed to analyze fewfrequencies and the resulting tape 8 on each CPU can be combined using COMBIN

to run MOTION.

17) The coherent and incoherent Tapes 8 can be used in MOTION to get responsespectra and ZPA. MOTION is the same as Rev 2.

18) The incoherent option does not allow computation of member forces and stresses atthis time. However, since member forces are typically low frequency responses, useof coherent results for members forces are considered adequate.