Even though the deformation patterns are similar for both linear and nonlinear analyses, the
stress patterns differ. Though the horizontal loads are in opposing directions in the lug,
the stress distribution in the web for the linear run are the same around both the lug holes
which is not correct. This happens as all the gaps are in a closed condition for the linear
analysis. Nonlinear gap analysis gives more accurate representation. The gap status, open or
closed, depending on loading condition can also be observed from the
.out file:
ITERATION 0
Starting load increment 1 Current increment 1.0000E-01
Subcase 1 Load step: 1.0000E-01
--------------------------------------------------------------------------------
Nonlinear Err. Measures Gap and Contact Element Status MaxEquiv
Iter Avg. U EUI EPI EWI Open Closed Stick Slip Frozen PlasStrn
--------------------------------------------------------------------------------
1 5.24E-06 9.90E+01 1.17E+00 1.17E+00 23 25 0 0 0 0.00E+00
2 5.30E-06 2.10E-02 3.29E+01 1.90E+00 22 26 0 0 0 0.00E+00
3 5.30E-06 6.54E-05 1.72E-11 1.31E-14 22 26 0 0 0 0.00E+00