Does Angling a pin support on a truss change anything?

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SUMMARY

The discussion centers on the impact of angling a pin support at 30 degrees on the external reactions in a simple 2D truss system. Participants agree that while the pin support still provides vertical and horizontal reactions, the angle may influence the resultant forces acting on the support. A free body diagram is essential for accurately analyzing the forces and stresses involved, particularly when external loads, such as a 15kN downward force, are applied. The consensus is that the pin's angle does not inherently change the external reactions unless horizontal loads are introduced.

PREREQUISITES
  • Understanding of basic truss mechanics
  • Knowledge of free body diagram construction
  • Familiarity with reaction forces in structural analysis
  • Experience with point loads and their effects on structures
NEXT STEPS
  • Study how to construct free body diagrams for truss systems
  • Learn about the effects of angled supports on reaction forces
  • Investigate the principles of static equilibrium in structures
  • Explore advanced topics in structural analysis, such as moment distribution
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Civil engineers, structural analysts, and students studying mechanics of materials who are interested in understanding the effects of support angles on truss behavior.

CallumTheMan
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Homework Statement


If you had a simple 2D truss with a pin and a roller support, would making the pin on a 30 degree incline change the supporting reactions?

Homework Equations

The Attempt at a Solution


Can't see why since it still supports a horizontal and vertical, don't know hwy the angle would change anything?
 
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How did you determine that it does not change anything? Did you draw a diagram and work out the forces and stresses?
How are is the pin usually angled IRL - did you have a look?
 
Simon Bridge said:
How did you determine that it does not change anything? Did you draw a diagram and work out the forces and stresses?
How are is the pin usually angled IRL - did you have a look?
Okay so, imagine a basic truss that has a roller on the left side and a pin on the right. The pin on the right it angled at 30 degrees so instead of it sitting under the end perpendicular to the truss, its tilted by 30 degrees. Does tilting the support change the external reactions?
 
See attached
 

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CallumTheMan said:
Okay so, imagine a basic truss that has a roller on the left side and a pin on the right. The pin on the right it angled at 30 degrees so instead of it sitting under the end perpendicular to the truss, its tilted by 30 degrees. Does tilting the support change the external reactions?
It depends.

Are you more concerned with the reactions in the pin itself, or are you concerned with the forces at the base of the pin holder?
 
SteamKing said:
It depends.

Are you more concerned with the reactions in the pin itself, or are you concerned with the forces at the base of the pin holder?

Yeah I am concerned with just the external reactions of the pin support. Like in that picture I added, would tilting the support 30 degrees underneath the truss create a horizontal reaction? or would it still be 0 because there is no horizontal load?

PS. there are point loads on the truss at joints but none at the pin support and none are angled or horizontal
 
As always, if you want to know what is going on in the pin and its foundation, make a free body diagram and analyze it.
 
Can you please demonstrate how to draw the free body diagram start from the 30 degrees angled pin support? Let's say we put an external load 15kN pointing downward at top left corner of the truss. How to find the reaction forces at both roller and pin support? Do we consider the actual 2 reaction forces of the pin support as resultant force and both of them have their own horizontal and vertical forces?
 

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