Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

548 CHAPTER 19 Structural Idealization

Therefore,theresultantshearforceactingonthewebistheproductoftheshearflowandthelengthof
thestraightlinejoiningtheendsoftheweb;clearly,thedirectionoftheresultantisparalleltothisline.
ThemomentMqproducedbytheshearflowq 12 aboutanypointOintheplaneofthewebis,from
Fig.19.10,

Mq=

∫^2

1

q 12 pds=q 12

∫^2

1

2dA

or

Mq= 2 Aq 12 (19.10)

inwhichAistheareaenclosedbythewebandthelinesjoiningtheendsofthewebtothepointO.This
resultmaybeusedtodeterminethedistanceofthelineofactionoftheresultantshearforcefromany
point.FromFig.19.10,

Se= 2 Aq 12

fromwhich

e=

2 A

S

q 12

Substitutingforq 12 fromEq.(19.9)gives

e=

2 A

L 12

Fig.19.10

Moment produced by a constant shear flow.