# Roller Support Reactions in Structural Analysis

A roller support provided to a structure can be either a single roller or roller support and double roller support.

 Roller Support for a Steel Bridge

### 1. Roller Support or Single Roller Support Reactions

A single roller support restraints the movement of support only along the one translation direction. A roller support can be placed in two ways as shown in figure-2 and figure-3 below.

 Fig.2. Roller Support

When the roller support is provided as shown in fig.2, the support end A is allowed to rotate and to move along x-direction. i.e. Î”x≠ 0; and Î”Î¸≠ 0. But, the support restrains the movement of end along y-direction i.e Î”y=0; as a result of which, a reaction is developed i.e. Ry.

So for the below configuration of roller support, the number of support reactions = re = [Ry] = 1;

When the roller support is provided as shown in fig.3, the support end A is allowed to rotate and to move along y-direction. i.e. Î”y≠ 0; and Î”Î¸≠ 0. But, the support restrains the movement of end along y-direction i.e Î”x=0; as a result of which, a reaction is developed i.e. Ry.

 Fig.3. Roller Support

So for the below configuration of roller support, the number of support reactions = re = [Rx] = 1;

### 2. Double Roller Support

A double roller support similar to single roller, they restricts translational movement in one direction and also restrains rotational movement. A double roller support can be placed in following ways as shown in fig.4 and fig.5.

 Fig.4. Double Roller Support

When the roller support is provided as shown in fig.3, the support end A is allowed  to move along y-direction. i.e. Î”y≠ 0. But, the support restrains the movement of end along x-direction i.e Î”x=0; and rotational movement Î”Î¸= 0 as a result of which, a reaction is developed i.e. Rx and M.

So for the above configuration of double roller support, the number of support reactions = re = [Rx,M] = 2;

When the roller support is provided as shown in fig.4, the support end A is allowed  to move along y-direction. i.e. Î”x≠ 0. But, the support restrains the movement of end along x-direction i.e Î”y=0; and rotational movement Î”Î¸= 0 as a result of which, a reaction is developed i.e. Ry and M.

 Fig.5. Double Roller Support

So for the above configuration of double roller support, the number of support reactions = re = [Ry,M] = 2;