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Publication Number: FHWA-RD-01-113
Date: October 2002


Back-Calculation of Layer Parameters for LTPP Test Sections, Volume II

Figure 31. Flow chart showing the overall back-calculation process for the linear and nonlinear material characterization modules in MODCOMP4

1. IMS -- LTPP Database. Go to Number 2.

2. Extract data from IMS to create MODDATA.EXE input files for the linear module. Go to Number 3-8.

3. CONTROL.EXE (Reference data). Go to Number 11 Execute MODDATA.EXE.

4. INV_MOD.EXE (Inventory data). Go to Number 11 Execute MODDATA.EXE.

5. TST_MOD.EXE (Testing data). Go to Number 11 Execute MODDATA.EXE.

6. TEMP_MOD.EXE (Deflection-temperature data). Go to Number 11 Execute MODDATA.EXE.

7. GEN_FWD.SQL (Deflection data), then Execute DEFLAVG4.EXE (Deflection data), then Test Section and deflection basin characterization -- Remove Type I and III basins and establish subsections -- Average deflections per drop height. Go to Number 11 Execute MODDATA.EXE.

8. STIBASE (depth to rigid layer) and subgrade layer/thickness from boring log/shoulder probe. Go to Number 15 Execute PREMOD.EXE.

9. Extract results from the linear solutions to establish the initial properties for the nonlinear module. Go to Number 10.

10. Execute BASIN.EXE (Nonlinear). Go to Number 11.

11. Execute MODDATA.EXE (create PREMOD input file) Go to Number 12 and Number 13.

12. Automatic Layering. Establishes layer combination file and estimates "seed" modulus of each pavement layer. Go to Number 14.

13. Manual Override. LAY_COMD.DAT, SEET.DAT, ISDMOIST.DAT, SUBSECT.DAT. Go to Number 14.

14. Execute METRIC.EXE. Go to Number 15.

15. Execute PREMOD.EXE (create MODCOMP4 input file); TOL, CONVRATE; MAXITER, OUTSYLE, MODEL, STIFBASE.DAT. Go to Number 16 and to Number 17.

16. Execute MODSHELL on random deflection basins and revise inputs, if necessary. Then go back to Number 15.

17. Execute BACHIT.EXE. Go to Number 18.

18. Execute MODCOMP4.EXE (create output files with elastic modulus/property results). Go to Number 19 and Number 20.

19. Nonlinear -- Execute BACKSMNL and BAKOUTNL.

20. Linear -- Execute BACKSUM2. Go to Number 9.