Warning Message: maximum stiffener spacing was exceeded

[Phil]

If you are designing with a stiffened panel that is very slim (i.e. y-span is very small), you might get a warning message that says:

" Component set to max gage because maximum stiffener spacing was exceeded..."
 
Also, in the log file, you might see this message:

 Warning 4993, the --Sx-- spacing is too wide for
 the Panel Span width, 3 stiffeners are required.
 This permutation has been kicked out for:
 Component=       1     Spacing=  5.9055     Panel Span Y = 17.3228
 The next combination is being attempted.
 This message is issued only once per component.

This is not an error condition. Rather HyperSizer requires that a panel have at least 3 stiffeners in a panel span.  The reason for this message is that HyperSizer models stiffened panels using a "smeared stiffness" approach.  Our judgment is that with less than three stiffeners, the smeared panel assumption is no longer valid, therefore we require at least three. 

If the y-span is set such that less than 3 times the panel for a particular candidate design, that design is rejected.  In the above example, the y-span is 17.3 and the spacing is 5.9, therefore since 3*5.9 = 17.7 > 17.3, this candidate design is rejected and the software will go to the next candidate.

[jwbingenheimer]

In the above example, if the y-span was 17.3 (exactly 3 times stiffener spacing)and you are using the bonded hat panel family, will HyperSizer compute the smeared property of that panel assuming one full stringer in the center of the panel and a half stringer on each end of the panel, or will HyperSizer assume all three stringers are fully present in the 17.3 spacing?

Thanks

[James]

In terms of formulating the smeared panel stiffness, there are two ways you can think about it.

1. Two full stiffeners in the middle and two 1/2 stiffeners on the edges.
2. Three full stiffeners in the middle with 1/2 spacing skin on the edges.

Either way, the smeared approach will return the same panel-level stiffness matrix. When the strains are localized down into the panel objects (skin, stiffener web, flanges, etc) think of more in terms of a single stringer section with 1/2 skin on each side of the stiffener.

Here are a few links to some help sections that better describe the approach.
http://hypersizer.com/help/#StressAnalysis/sa-smeared_stiffness.php
http://hypersizer.com/help/#TestData/td-stiffened_panel_test_predict.php

-James