594 CHAPTER 22 Wings
Fig.22.7
Shear stress (N/mm^2 )distribution in wing section of Example 22.2.
Fig.22.8
N-cell wing section subjected to shear loads.
22.4 Shear...................................................................................................
Initially,weshallconsiderthegeneralcaseofanN-cellwingsectioncomprisingboomsandskinpanels,
thelatterbeingcapableofresistingbothdirectandshearstresses.Thewingsectionissubjectedtoshear
loadsSxandSy,whoselinesofactiondonotnecessarilypassthroughtheshearcenterS(seeFig.22.8);
theresultingshearflowdistributionisthereforeduetothecombinedeffectsofshearandtorsion.
Themethodfordeterminingtheshearflowdistributionandtherateoftwistisbasedonasimple
extensionoftheanalysisofasingle-cellbeamsubjectedtoshearloads(Sections16.3and19.3).Such
a beam is statically indeterminate, the single redundancy being selected as the value of shear flow
at an arbitrarily positioned “cut.” Thus, theN-cell wing section of Fig. 22.8 may be made statically
determinateby“cutting”askinpanelineachcellasshown.Whiletheactualpositionofthese“cuts”is
theoreticallyimmaterial,thereareadvantagestobegainedfromanumericalpointofviewifthe“cuts”
are made near the center of the top or bottom skin panel in each cell. Generally, at these points, the
redundantshearflows(qs,0)aresmallsothatthefinalshearflowsdifferonlyslightlyfromthoseofthe