- Thread starter
- #1

#### bergausstein

##### Active member

- Jul 30, 2013

- 191

- Thread starter bergausstein
- Start date

- Thread starter
- #1

- Jul 30, 2013

- 191

- May 27, 2012

- 47

When trying to solve these kind of problems try to find the stress of the nodes where there are only

But if you chose node C next you will find there are three unknowns. So my advice is analyse the Node B (which has only two unknown stresses) before going for node C. From there you can find the stress of the joint $F_{BC}$.

Now you'll only have two unknowns in node C since $F_{AC}$ and $F_{BC}$ is known.

- Thread starter
- #3

- Jul 30, 2013

- 191

can you help me create the free body diagram at joint B. thanks!

- May 27, 2012

- 47

$$\begin{align}

\rightarrow \displaystyle \Sigma \vec F &= 0\\

F_{AB} \sin \alpha - F_{BD}\sin{\beta} &= 0

\end{align}$$

$$\begin{align}

\uparrow \displaystyle \Sigma \vec F &= 0\\

F_{AB} \cos \alpha + F_{BD}\cos{\beta} +F_{BC} -400&= 0

\end{align}$$

I think you can find the appropriate values for $\alpha$ and $\beta$. $F_{AB}$ is known from node A (please consider that I've taken stress of the arm AB as a compression while you've taken it as a tension).

- Thread starter
- #5

- Jul 30, 2013

- 191

I did find the angle $\alpha$ but I don't know how to find angle $\beta$. can you help me find it.

- May 27, 2012

- 47

- Thread starter
- #7

- Jul 30, 2013

- 191

$\beta=$63.4 degrees am I correct?

- May 27, 2012

- 47

Yes that's correct. I hope you can manage to find the other stresses.

- May 13, 2013

- 386

how can we solve this using method of sections?