Four L-shaped members: Mechanical Analysis Problem

Thread starter jojosg
Start date Dec 26, 2025

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SUMMARY

This discussion focuses on determining the support reactions at points A and B for a system of four L-shaped members in a mechanical analysis problem. The participants emphasize the importance of applying the equations of equilibrium, specifically the three scalar static equations for each rigid body. They clarify that the internal forces at joints should be ignored when calculating moments and that the number of equations must match the number of unknowns, which is 12 in this case. The final equations derived include expressions for the forces at joints B and E, as well as the overall equilibrium conditions for the structure.

PREREQUISITES

Understanding of static equilibrium principles in mechanics
Familiarity with free body diagrams (FBD) for rigid bodies
Knowledge of scalar static equations for planar problems
Ability to apply moment balance in mechanical systems

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Study the application of the equations of equilibrium in multi-body systems
Learn how to construct and analyze free body diagrams for complex structures
Explore the concept of internal forces and their role in mechanical analysis
Investigate the methods for solving simultaneous equations in statics

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Mechanical engineers, civil engineers, and students studying mechanics who are involved in analyzing static structures and determining support reactions in multi-member systems.

Monday, 7:59 AM

Steve4Physics

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jojosg said:

I used basic trigo and drew a triangle with adjacent and opposite sides both a to get 45 degrees

Note that this is only justified because section DG is in equlibrium with only 2 forces acting on it.
So:
a) the 2 forces must have equal magnitudes and opposite directions;
b) the 2 forces must have a common line-of-action (dashed line, below).so that these forces have zero net moment.