Supports

Question 1

Fixed supports

Answer 1

A fixed support is the most rigid type of support or connection. It constrains the member in all translations and rotations (i.e. it cannot move or rotate in any direction). The easiest example of a fixed support would be a pole or column in concrete. The pole cannot twist, rotate or displace; it is basically restricted in all its movements at this connection.

Question 2

Applications of fixed supports

Answer 2

Fixed supports are extremely beneficial when you can only use a single support. The fixed support provides all the constraints necessary to ensure the structure is static. It is most widely used as the only support for a cantilever.

Question 3

Limitation of fixed supports

Answer 3

Fixed supports offers absolutely no ‘give’. In a sense, its greatest advantage can also be its downfall, as sometimes a structure requires a little deflection or ‘play’ to protect other surrounding materials.

Question 4

Pin supports

Answer 4

pinned support allows rotation to occur but no translation (i.e. it resists horizontal and vertical forces but not a moment).

Question 5

Limitation of pinned supports

Answer 5

A single pinned support can not completely restrain a structure, as you need at least two supports to resist the moment.

Question 6

Application of pinned supports

Answer 6

Pinned supports are commonly utilized in trusses by connecting multiple members with hinge connections. This arrangement causes the members to push against each other, resulting in an axial force within each member. The advantage of this setup is that it eliminates internal moment forces within the members, allowing them to be designed based solely on their axial force.

Question 7

Roller support

Answer 7

can resist a vertical force but not a horizontal force. A roller support or connection is free to move horizontally as there is nothing constraining it.

Question 8

Application of roller support

Answer 8

a bridge will typically contain a roller support at one end to account for vertical displacement and expansion from changes in temperature. This is required to prevent the expansion causing damage to a pinned support.

Question 9

Limitation of roller support

Answer 9

This type of support does not resist any horizontal forces. This obviously has limitations in itself as it means the structure will require another support to resist this type of force.

Question 10

Simple support

Answer 10

A simple support is basically just where the member rests on an external structure. They are quite similar to roller supports in the sense that they are able to restrain vertical forces but not horizontal forces.

Question 11

Limitation of simple support

Answer 11

Simple supports aren’t widely used in real-life structures unless the engineer can be sure that the member will not translate; otherwise, they run the risk of the member simply falling off the support.