# Max bending moment

## Homework Statement

The beam ABCD in question is 10m long with supports at A and C. At B there is a 50KN point load and another 20Kn point load at D. The is a uniform load between A and c of 30KN/m.
A is 8m from C, A is also 2m from b and d is 2m from c.

I need to find the max bending moment but i also need a step by step guide on how to work it out?

I roughly know it should be around 280.

The reactions at A and C are 152.5 and 157.5 respectively.

If possible could you show me how to calculate the distance from support A that the max bending moment would occur?

I also need the point of contraflexure and the postion relative to A as well?

## The Attempt at a Solution

I have made numerous attempts but get know where near the answer i know it should be.

Thanks for the help.

SteamKing
Staff Emeritus
Homework Helper
Step 1: Draw a diagram of your beam, including the given loads, and show the location of points A B C D, using dimensions as necessary.

Step 2: Can you find the reactions at A and C using the equations of statics?

Ive drawn the beam and worked out the reactions, where do i go from there to calculate the max bending moment?

Is the max bending moment equal to the of moment about D i.e.

2x V2 -40 +m = 0

where V2 is the reaction at C i.e. 2 x 157.5

Giving me 275.

Is this correct?

SteamKing
Staff Emeritus
Homework Helper
No. Now that you have calculated your reactions, work out what the shear force diagram looks like along the length of the beam. And I calculate a different reaction at C. Please show your work for calculating the reactions.

reaction at C

8x V2 -(30x8x4) - 50x2 -20x10=0

8V2 = 1260
V2 = 157.5

Reaction at A

8V1 - (30x8x4) -50x6 +2 x 20
8V1= 1220

V1 = 152.5

Is that not right?

SteamKing
Staff Emeritus