How Can You Correctly Calculate Forces in a Truss Analysis Problem?

[lecammm]

Homework Statement

As shown by the attachment we are given the distances and the 28kN force

Homework Equations

relevant equations are equations of equilibrium;

ƩFy & ƩFx = 0;
ƩM = 0;

The Attempt at a Solution

First found By by summing the moments around point A;
(clockwise positive)
i.e.

ƩMa = (28*0.6) - (By*0.3) = 0

which gave By = 56kN

Next I summed the forces in the x direction and then took the sum of moments around the point "C", then tried to solve the simultaneous equations for Bx

However, this gave the wrong answer and I have no idea where to go.

Any help is great, thanks :D

 

[Andrew Mason]

Homework Statement

As shown by the attachment we are given the distances and the 28kN force

Homework Equations

relevant equations are equations of equilibrium;

ƩFy & ƩFx = 0;
ƩM = 0;

The Attempt at a Solution

First found By by summing the moments around point A;
(clockwise positive)
i.e.

ƩMa = (28*0.6) - (By*0.3) = 0

which gave By = 56kN

Next I summed the forces in the x direction and then took the sum of moments around the point "C", then tried to solve the simultaneous equations for Bx

However, this gave the wrong answer and I have no idea where to go.

Any help is great, thanks :D

What is the moment about A of the force applied at C by the CB support? What does that tell you about the x component of force at C and at B?

AM