Pinned support

Definition

A pinned support is a type of structural support that allows a structure to rotate but not translate in any direction, providing a point of connection between structural elements. This support type is crucial in analyzing both determinate and indeterminate structures, as it can effectively transfer loads while accommodating movement due to temperature changes or applied forces. Pinned supports help maintain structural stability while allowing for necessary deformations.

5 Must Know Facts For Your Next Test

1. Pinned supports provide two reactions: one vertical and one horizontal, which helps balance the forces acting on a structure.
2. In a pin-jointed frame, the pinned supports allow for rotations at the joints, leading to simpler calculations in structural analysis.
3. Pinned supports do not resist moments, meaning they cannot hold any twisting forces, making them suitable for certain types of structures where moment resistance is not required.
4. These supports can be found in various structures, including bridges and trusses, where they help distribute loads effectively.
5. When analyzing indeterminate structures, the role of pinned supports becomes more complex as additional constraints need to be considered for overall stability.

Review Questions

• How do pinned supports influence the analysis of determinate and indeterminate structures?
  • Pinned supports play a critical role in both determinate and indeterminate structures by providing specific types of reactions that influence the overall equilibrium of the system. In determinate structures, they allow for straightforward calculations since all forces can be resolved with basic equilibrium equations. In contrast, in indeterminate structures, pinned supports create additional equations due to the presence of redundant constraints that must be analyzed to ensure overall stability and load distribution.
• Discuss the advantages and disadvantages of using pinned supports in structural designs.
  • The primary advantage of using pinned supports is their ability to allow rotations while preventing translation, which provides flexibility in accommodating movements such as thermal expansion. This flexibility aids in reducing stress concentrations within the structure. However, the disadvantage lies in their inability to resist moments, meaning they are not suitable for all applications, particularly where twisting forces are present. This limitation necessitates careful consideration in design to ensure that structural integrity is maintained under varying load conditions.
• Evaluate the impact of pinned supports on load distribution within complex truss systems.
  • In complex truss systems, pinned supports significantly affect load distribution by allowing certain joints to rotate freely. This rotation means that the internal forces within members can change based on how loads are applied, leading to more efficient load transfer throughout the truss. As a result, understanding the behavior of pinned supports is essential when evaluating how these systems perform under dynamic conditions. By recognizing how loads distribute through these supports, engineers can optimize truss designs for strength and weight efficiency.

Related terms

roller support:

A type of support that allows for horizontal movement but prevents vertical displacement, often used to accommodate thermal expansion.

moment resistance: The ability of a structural element to resist bending moments, which is important when considering how forces are distributed in beams and frames.

static equilibrium: The condition where the sum of forces and moments acting on a structure is zero, essential for analyzing the stability of structures.