CHAPTER 18 Combined Open and Closed Section Beams..........................................
Sofar,inChapters15through17,wehaveanalyzedthin-walledbeamswhichconsistofeithercompletely
closed cross sections or completely open cross sections. Frequently, aircraft components comprise
combinationsofopenandclosedsectionbeams.Forexample,thesectionofawingintheregionofan
undercarriagebaycouldtaketheformshowninFig.18.1.Clearly,partofthesectionisanopenchannel
section, while the nose portion is a single cell closed section. We shall now examine the methods of
analysisofsuchsectionswhensubjectedtobending,shear,andtorsionalloads.
18.1 Bending...............................................................................................
Itisimmaterialwhatformthecrosssectionofabeamtakes;thedirectstressesduetobendingaregiven
byeitherofEq.(15.18)orEq.(15.19).
18.2 Shear...................................................................................................
The methods described in Sections 16.2 and 16.3 are used to determine the shear stress distribution,
although, unlike the completely closed section case, shear loads must be applied through the shear
centerofthecombinedsection;otherwise,shearstressesofthetypedescribedinSection17.2dueto
torsionwillarise.Whereshearloadsdonotactthroughtheshearcenter,itspositionmustbefoundand
theloadingsystemreplacedbyshearloadsactingthroughtheshearcentertogetherwithatorque;the
twoloadingcasesarethenanalyzedseparately.Again,weassumethatthecrosssectionofthebeam
remainsundistortedbytheloading.
Fig.18.1
Wing section comprising open and closed components.
Copyright©2010,T.H.G.Megson. PublishedbyElsevierLtd. Allrightsreserved.
DOI:10.1016/B978-1-85617-932-4.00018-X 529