# Bending of Beams

## Homework Statement

Calculate the reaction forces at B and D

See attached jpeg.

## The Attempt at a Solution

sum of vertical forces

By + Dy = 7 + (9*5)

Do I then solve for the moment about D or A or B?

for moment about D i have: -Dy -7 -(9*5)+9By+(12*2)=0

is this correct, please explain to me the process of and how I should go about these problems

#### Attachments

• fig.jpg
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SteamKing
Staff Emeritus
Homework Helper
The moment equation you have written is incorrect. For example, what is the moment of the 7 kN force about D? Remember, the sign of the moment is important. The moment of the distributed load is also incorrect. I don't know why you are multiplying the applied moment of 12 kNm by 2.

The moment equation you have written is incorrect. For example, what is the moment of the 7 kN force about D? Remember, the sign of the moment is important. The moment of the distributed load is also incorrect. I don't know why you are multiplying the applied moment of 12 kNm by 2.

When the moment is clockwise to the left of the point it is positive?

9By +12 - (9*5*2.5) -(7*4) = 0

Is that correct now?

SteamKing
Staff Emeritus
Homework Helper
On the moment of the distributed load, remember the center of the load must be taken about point D. Check your moment arm.

On the moment of the distributed load, remember the center of the load must be taken about point D. Check your moment arm.

9By +12 - (9*5*6.5) -(7*4) = 0

By= 34.28

I'm am still a bit unclear on the moments when they are positive and negative, is what I said before correct, when they are to the left of the point and clockwise , they are positive?

SteamKing
Staff Emeritus