Support Reaction

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Let’s first define support before going further into support reactions. Supports are constructions that incorporate beams, columns, and other components to sustain a load. In engineering mechanics, supports come in a variety of forms. Some examples of these types are simple supports; roller supports, pin-joint supports, fixed supports, and smooth surface supports.

Support Reactions can be forces acting on supports or end moments acting as restraints due to immobilization. Support reactions and external forces operating on structural systems are in equilibrium. Discuss support reactions in detail, including their categories and appropriate examples.

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What is Support?

An element of a structure known as structural support offers the rigidity and strength required to withstand internal forces and safely direct them to the ground. Support structures experience internal forces (forces coupled by the rest of the structure) due to external loads (the actions of other bodies) acting on the building.

Supports, also known as connectors, joints, or restraints, can be found at the beginning, end, or any other intermediate point along a structural member or constituent component of a structure. Hinged support in the beam can offer reaction in vertical and horizontal directions.

Types of Support and Reaction

A member who supports other members by assisting them in resisting loads is a structure member. Structure supports transfer load to the ground and provides stability to the structure they support. The types of support can be divided into two categories.

  • External Supports
  • Internal Supports

External Structural Support and Support Reaction

External supports are typically provided externally without interfering with the structural elements. The following list includes various types of external supports:

  • Fixed support
  • Pinned support or hinged support
  • Roller support
  • Rocker support
  • Link support
  • Simple support

Fixed Support Reaction

Rigid supports are another name for fixed supports. Fixed supports can withstand any force or moment since they are constrained against rotation and translation. Three unknowns in the structural analysis must be determined for fixed support that can fulfill each of the three equilibrium equations. The construction should have at least one hard support to ensure optimum stability. A beam fastened to the wall is an example of fixed support. The number of reaction components at fixed support is 6.

Pinned Support Reaction

Pinned or hinged supports can withstand vertical and horizontal stresses, but not moments. It indicates that the hinged support is prohibited from translating. Identifying the elements of horizontal and vertical forces is possible using equilibrium equations. The finest example of hinged support is a door leaf, which only moves vertically and does not move horizontally or vertically. Only one direction of a pinned or hinged support is permitted; all other rotation directions are opposed.

Roller Support Reaction

Roller supports can only withstand perpendicular forces; they are incapable of withstanding parallel or horizontal forces. It implies that the roller support will travel freely over the surface while not buckling under horizontal pressure. This support is offered at the far end of a bridge span. Roller support is provided at one end to allow the bridge deck to contract or expand in response to variations in atmospheric temperature. So the answer to the question, Roller support carries how many unknown reactions? is one or two.

Rocker Support and Support Reaction

Similar to roller support is rocker support. Additionally, it defies vertical pressure and permits both horizontal movement and rotation. However, the bottom-provided curved surface causes horizontal movement in this instance. The quantity of horizontal movement is therefore constrained in this case.

Link Support and Support Reaction

The link as support permits only rotation and translation perpendicular to the direction of the link. Translation in the direction of the link is not permitted. It has a single linear resultant force component that can be broken down into vertical and horizontal components in the direction of the link.

Simple Supports in a Structure and Their Reactions

Simple support is nothing more than support for a structural part. Like roller supports, they are incapable of resisting lateral movement and moment. They only withstand vertical support movement when assisted by gravity. To a certain point, horizontal or lateral movement is permitted, but the structure loses stability beyond that point. It resembles two bricks sitting longitudinally on one another. The number of reaction components for simple support is 3.

Internal Support and Support Reaction

Internal supports are given internally in the structural member, dividing the entire member into separate pieces. As a result, it is possible to identify the external reactions for each component, which will make analysis much simpler. The types of internal supports that are offered in a structure are as follows:

  • Internal hinge
  • Internal roller

Internal Hinge Support in a Structure

Internal hinges resist translation in all directions and only permit rotation, similar to hinge supports. In structures, internal hinges are given for axial members, while middle hinges are provided for beam members. These are frequently found in the middle of bridges with arches. The number of independent reaction components for hinged support is 6. Hinged support in the beam can offer reaction in vertical and horizontal directions.

Internal Roller Support in a Structure

Like external roller supports, internal roller supports are placed in the center of a structural element. A structure’s internal roller support moves large items or members from one location to another using the horizontal movement of the support; internal roller supports of this type are utilized in tower cranes or harbor cranes.

S. no.

Types of Support

Support Reaction

Resisting Load


Roller Support


Vertical Loads


Pinned Support

Horizontal and Vertical

Horizontal and Vertical Loads


Fixed Support

Horizontal, Vertical, and Moments

All Types of Loads are Horizontal, Vertical, and Moments


Simple Support


Vertical Load

Significance of Support Reaction

Structural support is a component of a building or structure that offers the required rigidity and strength to withstand internal forces and safely direct them to the ground.

A support reaction might be a force acting on support or an end moment that follows an impossible movement. Support reactions and external forces operating on structural systems are in equilibrium.

Important GATE Topics

Work Done By A Force Motion Under Gravity
Dynamic Resistance Static Resistance
Ideal Diode Bettis Theorem
Work Done By A Constant Force Application Layer Protocols
Castigliano’s Theorem Portal Frames

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