Page 191 - Buried Pipe Design

Design of Gravity Flow Pipes 165

Also incorporated is a data check sequence where the element infor-
mation is processed to test if the data have been input correctly. Soil
elements which have been evaluated on the unloading model are iden-
tified by their stress level. Unloading and rebound elements have a
negative stress level.

Additional output. There are several additional output files that have
been included in PIPE5 to accommodate data processing. For each
loading increment, the user has the option of having the results
printed on separate files. The option includes having the stresses,
strains, and displacements printed to separate output files. This
allows the user to use the stresses, strains, and displacements as pre-
existing stresses for any subsequent runs.
In addition to having an option to printing particular results to sep-
arate output files, an option is included to have the ring deflections
separately printed to an output file. This option exists for every load
increment. Combinations of ring deflection files and/or stress, strain
displacement files are included. Results of a given run can be easily
viewed by examining the load-deflection curve; therefore, viewing the
ring deflection file facilitates a much faster review of the results.

Plotting. The PIPE5 program had been adapted to interactively dis-
play the results graphically. Several output files have been created
that are compatible with the plotting routines. The mesh information
is stored on a separate file that has a compatible format with mesh
plotting routines. Pipe strains are also printed out to a file that is used
to plot the strains versus position of the pipe. The ring deflection file
previously described is also used to plot the load-deflection curve for a
given analysis. Thus, the results of a given run can be analyzed
through the output files and presented interactively using the graphi-
cal user interface.

Example applications
Some results from applications of the FEA program PIPE are included
here and are compared with measured responses from actual tests
conducted in soil load cells at Utah State University (see Figs. 3.48
and 3.49). The comparisons that are shown are for pipe with a 10-lb/in 2
pipe stiffness. Test cell soil compaction conditions that are included for
comparisons are

1. Ninety percent relative compaction with homogeneous conditions
2. Ninety percent relative compaction with poor haunches
3. Eighty percent relative compaction with homogeneous conditions