How Do You Calculate Member Forces Using the Unit Load Method?

[EngineeringDave]

Hi I was hoping someone could clear something up for me, I've been set an virtual load (unit load method) question at University, that part of the question I can do however its the calculating the force on the members part that I am struggling with.

The question asks for all the forces in the members as a function of load P using the unit load method, however as there are 4 pin joints (Ay and Bx can cancel) and 4 bars using any equilibrium, joints or moment calcs I can't get each member only in terms of P.

Other students have removed members to do this however as this "method" they are using isn't in the course note and I can't find it online I don't want to just assume they are right.

I've drawn the system In the file uploaded.

Thanks In Advance

Dave

 

[SteamKing]

I think your frame is statically indeterminate. Your classmates are removing members in order to make the resulting determinate. It's much easier to apply the various analysis techniques to a determinate structure, in order to determine the additional equation or equations necessary to allow solution.

 

[EngineeringDave]

Okay thanks, I will research this today as I am unfamiliar with the concept.

Thanks Steamking

P.S can I message you with a related quire if I have one?