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I'm trying to construct a bending moment diagram for the situation as below:

[PLAIN]http://img42.imageshack.us/img42/633/bmdiag.jpg [Broken]

Where Ra and Rb are reaction forces, L1 and L2 are lengths between Ra and N and N and Rb respectively, N is a force acting perpendicular to the beam and P is a force acting at length L3 (sorry forgot to label this) parallel to the beam. The beam has fixed ends so cannot hinge.

The shear force diagram is fairly straight forward, but I'm having issues trying to decide whether to include P in the first "cut" between Ra and N.

What I've done so far is:

If you take x from the left hand side, then between Ra and N:

M= Ra*x

between N and Rb:

M= Ra*x - L3*P - N*(x-0.1)

However, when this is plot it looks very strange as suddenly the magnitude changes drastically when L3*P is included.

What have I done wrong?

Thanks,

Kalus

[PLAIN]http://img42.imageshack.us/img42/633/bmdiag.jpg [Broken]

Where Ra and Rb are reaction forces, L1 and L2 are lengths between Ra and N and N and Rb respectively, N is a force acting perpendicular to the beam and P is a force acting at length L3 (sorry forgot to label this) parallel to the beam. The beam has fixed ends so cannot hinge.

The shear force diagram is fairly straight forward, but I'm having issues trying to decide whether to include P in the first "cut" between Ra and N.

What I've done so far is:

If you take x from the left hand side, then between Ra and N:

M= Ra*x

between N and Rb:

M= Ra*x - L3*P - N*(x-0.1)

However, when this is plot it looks very strange as suddenly the magnitude changes drastically when L3*P is included.

What have I done wrong?

Thanks,

Kalus

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