MICHBACK is a computer program for the backcalculation of flexible and composite pavement layer properties using data obtained with a falling weight deflectometer (FWD).
The development of MICHBACK Version 1.0 for DOS was supported by the Michigan Department of Transportation and the University of Michigan Transportation Research Institute.
MICHBACK has many user-friendly features and advantages over other backcalculation programs. It:
MICHBACK Version 1.0 for DOS requires the following hardware and software:
Although not strictly required for the use of the program, the following hardware is strongly recommended:
The following files are included in this distribution of MICHBACK:
The supplied files can be used to generate screen images of most of the figures in the User's Manual without having to perform an analysis.
To install the program on a hard disk, first make a subdirectory to hold the program (e.g., MD \MICHBACK), change to this directory (e.g., CD \MICHBACK), and copy all the files in the distribution to this directory.
In the root directory, there is a file named "config.sys" which configures the PC system and loads any requested device drivers when the computer is turned on. The following statement will need to be added to the "config.sys" file, if it does not already exist:
The MICHPAVE program uses a Fortran callable graphics package called GRAFMATIC. Unfortunately, this package is not compatible with the "ansi.sys" device driver used by some other programs for screen manipulations. Thus, if the "config.sys" file has the statement
then this statement will need to be removed and the computer re-booted (by simultaneously pressing the CTRL, ALT and DEL keys) before running MICHBACK. If available, use of an "ansi.sys" compatible device driver that can be unloaded from memory on demand is convenient since it eliminates the need to re-boot the computer.
The MICHBACK program requires about 475 KB of free memory to run. DOS and memory resident programs reduce the amount of free memory for use by other programs. The amount of free memory available can be checked by using the DOS command MEM or CHKDSK. If there is insufficient free memory, then memory resident programs will need to be removed before running MICHBACK.
If there is insufficient memory to load the program, a message similar to that shown below will be displayed:
"Program too big to fit in memory."
Graphic screens produced by MICHBACK can be dumped onto an attached printer if the DOS command GRAPHICS.COM is issued after the computer is turned on and before MICHBACK is used. It may be convenient to include the command in the AUTOEXEC.BAT file so that it is issued every time the computer is turned on. To download graphics that are on the screen to the printer simply press the SHIFT and PRSCR keys simultaneously.
MICHBACK uses a modified Newton method to backcalculate pavement layer properties using FWD data. In addition to the layer moduli, the depth of a stiff layer (e.g., bedrock) or the thickness of one layer may also be backcalculated.
Surface deflections are computed using an extended precision version of the well-known CHEVRON program. The numerical quadrature in the original CHEVRON program has been improved so that deflections of stiff pavements are computed accurately.
Details of the backcalculation method can be found in the following publications:
Harichandran, R. S., Mahmood, T., Raab, A., and Baladi, G. Y. (1993). "A modified Newton algorithm for backcalculation of pavement layer properties." Transportation Research Record, 1384, 15-22.
Harichandran, R. S., Mahmood, T., Raab, A., and Baladi, G. Y. (1994). "Backcalculation of pavement layer moduli, thicknesses and bedrock depth using a modified Newton method." In Nondestructive Testing of Pavements and Backcalculation of Moduli (Second Volume), ASTM STP 1198, H. L. Von Quintas, A. J. Bush and G. Y. Baladi (eds.) American Society for Testing and Materials, Philadelphia, PA, 68-82.
MICHBACK is being combined with the MICHPAVE nonlinear finite element program to provided a self-contained mechanistic pavement design system (MPDS) for the Windows 95/NT operating system. Overlay design, AASHTO thickness design and elastic layer analysis will be included within MPDS. MPDS is scheduled to be released in 1999 or 2000.