Question

The influence line diagram for the force in member 'a' of the truss shown below is given by

• A.
• B.
• C.
• D.

Answer 1

The correct option is A




When unit load is at A
Force in GB = 0
When unit load is at E
Force in GB = 0
When unit load is at B,
$R_A=\frac{18\times 1}{24}=0.75$
$R_E=0.25$







$\frac{F_{GB}}{\sqrt{2}}=0.25$
$F_{GB}=0.25\sqrt{2}=0.354$
When unit load is at C






$\Rightarrow$ $\frac{F_{GB}}{\sqrt{2}}=0.5$
$\Rightarrow$ $F_{GB}=0.5\sqrt{2}=0.707$ (Comp).
When unit load is at D,





$\frac{F_{GB}}{\sqrt{2}}=0.25$
$F_{GB}=0.354$ (Compressive)
$\therefore$ ILD for force in member BG is