Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

23.1 Principles of Stiffener/Web Construction 621

Fig.23.3

Equilibrium of stiffener CJG in the beam of Example 23.1.

FromtheequilibriumofstiffenerJK,wehave

(q 1 −q 2 )× 250 =4000sin60◦=3464.1N (i)

andfromtheequilibriumofstiffenerHKD,

200 q 1 + 100 q 2 =4000cos60◦=2000N (ii)

SolvingEqs.(i)and(ii),weobtain

q 1 =11.3N/mm q 2 =−2.6N/mm

TheverticalshearforceinthepanelBCGFisequilibratedbytheverticalresultantoftheshearflowq 3.
Thus,

300 q 3 =4000cos60◦=2000N

fromwhich

q 3 =6.7N/mm

Alternatively,q 3 maybefoundbyconsideringtheequilibriumofthestiffenerCJG.FromFig.23.3,

300 q 3 = 200 q 1 + 100 q 2

or

300 q 3 = 200 ×11.3− 100 ×2.6

fromwhich

q 3 =6.7N/mm

Theshearflowq 4 inthepanelABFEmaybefoundusingeitheroftheabovemethods.Thus,considering
theverticalshearforceinthepanel,

300 q 4 =4000cos60◦+ 5000 =7000N