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

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SUMMARY

The discussion centers on calculating member forces using the Unit Load Method in a statically indeterminate frame with four pin joints and four bars. The user, Dave, struggles to express the forces in terms of the applied load P due to the complexity introduced by the indeterminate nature of the structure. A fellow participant, Steamking, confirms that removing members can simplify the analysis, making the structure determinate, which allows for easier application of equilibrium and moment calculations. Dave is encouraged to research the concept of statically indeterminate structures to better understand the necessary equations for solving the problem.

PREREQUISITES
  • Understanding of the Unit Load Method
  • Knowledge of statically indeterminate structures
  • Familiarity with equilibrium equations in structural analysis
  • Basic principles of force analysis in pin-jointed frames
NEXT STEPS
  • Research the concept of statically indeterminate structures
  • Learn about methods for simplifying indeterminate structures
  • Study equilibrium equations for multi-joint systems
  • Explore advanced techniques in structural analysis, such as the force method
USEFUL FOR

Students in civil or structural engineering, particularly those studying structural analysis and the Unit Load Method, as well as professionals seeking to deepen their understanding of member force calculations in complex frameworks.

EngineeringDave
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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
 

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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.
 
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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?
 

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