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Types of Support in Structural Engineering

December 31, 2024 | 5 min read

In structural engineering, the term “support” refers to the mechanism by which structures are held in place or stabilized. Supports are integral to the safety, stability, and functionality of any structure, from towering skyscrapers to simple bridges. Understanding the types of structural supports is essential for designing efficient and durable structures. In this article, we’ll delve into the primary types of supports, their applications, and how they affect structural behavior.

1. Pinned Support

A pinned support, also known as a hinge support, allows rotation but restricts translational movement in any direction. This means that the support can resist horizontal and vertical forces but cannot resist a moment (rotation).

Characteristics:
  • Resists horizontal and vertical forces
  • Allows rotation
  • Commonly represented in diagrams as a triangle or a hinge symbol
Applications:
  • Trusses: Pinned supports are often used in truss structures, such as bridges, to allow for some degree of rotation while ensuring stability.
  • Beams: In structural frames, pinned supports provide stability while accommodating slight rotations due to loads.
Example:
  • The ends of a simply supported beam typically use pinned supports.

2. Fixed Support

Fixed supports restrict all forms of movement: horizontal, vertical, and rotational. This type of support provides the highest degree of restraint and is capable of resisting moments as well as forces.

Characteristics:
  • Resists horizontal, vertical, and rotational forces
  • No movement is allowed
  • Represented by a filled triangle or a solid block in diagrams
Applications:
  • Retaining Walls: Fixed supports are crucial for retaining walls to prevent tipping or sliding.
  • Cantilever Beams: The fixed end of a cantilever beam ensures that the beam remains stable and can carry loads effectively.
  • High-Rise Buildings: Fixed supports provide foundational stability for tall structures to resist wind and seismic forces.
Example:
  • The base of a flagpole is a classic example of a fixed support.

3. Roller Support

Roller supports allow movement in one direction while restricting movement in the perpendicular direction. They cannot resist horizontal forces or moments but can resist vertical forces.

Characteristics:
  • Resists vertical forces only
  • Allows horizontal movement
  • Commonly represented as a roller or wheel symbol in diagrams
Applications:
  • Bridges: Roller supports are often used in bridges to allow for thermal expansion and contraction.
  • Long Beams: Structures experiencing temperature changes or shrinkage often incorporate roller supports.
  • Roof Trusses: Roller supports help accommodate temperature-induced movements in large roof structures.
Example:
  • The expansion joints in bridges are supported by rollers to accommodate thermal movements.

4. Simple Support

Simple supports are a combination of pinned and roller supports. They allow rotation and horizontal movement but restrict vertical displacement. These supports are commonly used in theoretical analyses and practical applications.

Characteristics:
  • Resists vertical forces
  • Allows rotation and horizontal movement
  • Represented as a triangle or a hinge in diagrams
Applications:
  • Beam Structures: Simple supports are often used in idealized beam analyses for simplicity.
  • Temporary Structures: Used in scaffolding and temporary bracing systems.
Example:
  • A beam resting on two columns with no fixed attachment is an example of a simply supported beam.

5. Sliding Support

Sliding supports are similar to roller supports but with less restriction. They allow translational movement in a specific direction while resisting movement in the perpendicular direction.

Characteristics:
  • Resists forces perpendicular to the movement direction
  • Allows sliding motion in one direction
Applications:
  • Heavy Machinery: Sliding supports are used to accommodate thermal expansion or operational movements in machinery.
  • Large Pipelines: Sliding supports help pipelines adjust to thermal expansion and contraction without stress.
Example:
  • Certain types of conveyor belt systems use sliding supports.

6. Cable Support

Cable supports are unique to structures where tension is the primary force. They allow for flexibility and are used in systems where loads are transferred through tension.

Characteristics:
  • Resists tension forces only
  • Provides high flexibility
Applications:
  • Suspension Bridges: Cables support the deck of suspension bridges by transferring loads to towers and anchorages.
  • Roof Structures: Tensioned cables are often used in tensile fabric structures.
  • Transmission Lines: High-tension cables for power transmission rely on cable supports.
Example:
  • The Golden Gate Bridge is a classic example of a structure using cable supports.

7. Rockers and Rocker Bearings

Rockers are specialized supports that allow rotation and some translational movement. They are typically used in large structures requiring flexibility due to dynamic forces.

Characteristics:
  • Allows rotation and slight movement
  • Resists vertical forces
Applications:
  • Large Bridges: Rocker bearings are used to accommodate thermal expansion and contraction.
  • Railway Bridges: Rocker bearings provide flexibility for dynamic loads from trains.
Example:
  • Historic arch bridges often feature rocker bearings at their supports.

8. Elastomeric Bearings

Elastomeric bearings are flexible supports made of rubber-like materials that allow controlled movement and rotation while resisting vertical loads.

Characteristics:
  • Resists vertical loads
  • Allows controlled translational and rotational movements
  • Provides vibration isolation
Applications:
  • Modern Bridges: Elastomeric bearings are widely used in bridge construction to absorb vibrations and accommodate movements.
  • Buildings in Seismic Zones: These supports help isolate structures from ground motion during earthquakes.
  • Industrial Equipment: Used to reduce vibrations in heavy machinery foundations.
Example:
  • Highway overpasses often use elastomeric bearings to improve durability and safety.

Conclusion

The choice of support in structural engineering is critical to the performance and longevity of a structure. Each type of support has unique characteristics that make it suitable for specific applications, from accommodating thermal expansion in bridges to providing stability for high-rise buildings. Understanding these differences allows engineers to design systems that are both efficient and resilient.

Whether you’re designing a simple beam or a complex suspension bridge, selecting the right type of support is the foundation for success. By mastering the principles behind structural supports, engineers can create structures that withstand the test of time and environmental challenges.

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