Help Needed: Determine Bending Moment at 0.600m from Roller Support

[laura001]

hey every1... I'm really really stuck on this problem and unless i get it and a few others right I am going to fail my engineering statics course :( Any help would be apreciated so much...


The Question that goes with that diagram I've attatched is:

Determine the bending moment at a distance x from the roller support on the left hand side, using the principles of virtual work.

The values are: F = 2kn, d=2.200m and x=0.600m

thankyou

 

[laura001]

another I am not sure about:

Each of the two uniform hinged bars have a mass m and length L. Both bars are connected by hinge S and supported as shown. The structure is loaded by a mass of 4m, applied at the hinge S. Gravitational acceleration is g = 9.81m/s2.

m= 15kg
L=5.500m
angle theta= 130 degrees

Calculate the torque Ma (in Nm) required for equilibrium

 

[radou]

hey every1... I'm really really stuck on this problem and unless i get it and a few others right I am going to fail my engineering statics course :( Any help would be apreciated so much...


The Question that goes with that diagram I've attatched is:

Determine the bending moment at a distance x from the roller support on the left hand side, using the principles of virtual work.

The values are: F = 2kn, d=2.200m and x=0.600m

thankyou

The attachment isn't working, but I can give you some directions. If the system has zero degrees of freedom (i.e. it's not a mechanism), you should make it a mechanism by putting a hinge at the point where you need to find the bendig moment (0.6 m). Draw a displacement sketch of that mechanism, so that you make the hinge rotate for a unit angle, and calculate all the displacement on the places of the loads (i.e. the force F). Then use the principle of virtual work: 'The necessary and sufficient condition for the equilibrium of a rigid body is zero virtual work done by all external forces acting on the particle during any virtual displacement consistent with the constraints imposed on the body.' It's a bit stupid to explain this like I just have - in a 'half-blind' manner, but I hope it helps.

P.S. The bending moment M you need to find acts at the place of the inserted hinge.

 

[laura001]

hey thanks for the reply! if i put the diagrams on a website can u maybe work them out please? i'd appreciate it so much, i usually don't do this but i have to have answers by 2moro which isn't long enough for me to learn about principles of virtual work... the diagram for the 1st Q is here:

http://img383.imageshack.us/my.php?image=q1cm6.jpg

and for the 2nd Q:

http://img407.imageshack.us/my.php?image=q2un0.jpg

P.S do u have msn radou?

 

[radou]

hey thanks for the reply! if i put the diagrams on phototube can u maybe work them out please? i'd appreciate it so much, i usually don't do this but i have to have answers by 2moro which isn't long enough for me to learn about principles of virtual work...

Go ahead, I hope I'll be able to help.