Draft

5.3Shear& Moment Diagrams 103

Reactions aredeterminedfromtheequilibriumequations

(+



) Fx= 0; ) RA

x

+ 6 = 0)RA

x

= 6k

(+


) MA= 0; ) (11)(4)+ (8)(10)+ (4)(2)(14+ 2)RFy(18)= 0)RFy= 14k

(+ 6 ) Fy= 0; ) RA

y

 11  8 (4)(2)+ 14 = 0)RA

y

= 13k

Sheararedeterminednext.

1. AtAtheshearis equalto thereactionandis positive.


2. AtBthesheardrops(negative load)by 11kto 2k.


3. AtCit dropsagainby 8kto 6 k.


4. It stays constant uptoDandthenit decreases(constant negative slope sincethe

loadis uniformandnegative) by 2kper linearfoot upto 14 k.

5. Asa check, 14 kis alsothereactionpreviouslydeterminedatF.

Momentis determinedlast:

1. Themoment atAis zero(hingesupport).


2. Thechangein moment betweenAandBis equalto theareaunderthecorresponding

sheardiagram,or
MBA= (13)(4)= 52.