The structure maintains the shape of things under the
force of gravity, the force of wind, or any other force

These structures have long elements (bars, tubes) The elements of frame structures are made of strong materials. The elements in the bicycle`s frame are the aluminium tubes; the unions are the aluminium welding, the nuts and bolts

Shell structures are made of a thin outer layer of material around a volume. There are many examples of natural shell structures: eggs, shellfish. There are also many examples of artificial shell structures: cardboard boxes, bottles, balloons, cars, aeroplanes.

In Roman times, arches were made of stones.
The geometry of the arch displaces the forces to the sides, so that there is a large free space under the arch.

Very often, we combine different types of structures into a more
complex structure
For example, houses have brick walls (mass structures)

• Examples of natural mass structures are mountains and coral reefs.
• Examples of man-made mass structures are sandcastles, dams, load-bearing walls (walls that support the weight of the building).

A suspension structure holds an element (often a beam) by cables that are held from the top of a tall column.
Because of this, suspension structures are often best for bridges that cover big rivers or even small parts of the sea

The foundation is an element united to the ground by friction.

The foundation is also united to the column by friction.

The column is another element, united to the foundation and to the primary beams.

These are for structures that we don’t need to disassemble.
Examples: welding, rivets, glue...

With non-permanent unions we can assemble and disassemble the elements of the structure.Examples: nuts and bolts, clamps, friction ..

This is the force that stretches an element. Tensional forces normally pull an element from
its ends.

This is the force which squeezes or buckles an element.
When an element “bends” in the middle due to the compression forces, it “buckles”.

The scissors produce a shear force in the paper bigger than it can withstand and one part completely slides over the other until they separate

If we apply a turning force (called “torque”) at one end of an element and, if the element is fixed to a support at the other end, the element twist.

Bending forces act at an angle to the element (at
90º in the drawing), making it bend

The design of the structure of an object (a beam for a house, the shell of a car, etc) helps reduce the amount of material used.
For example, we design the shell of a car so that the shell is as thin as possible to reduce weight.

We know the effects of forces on structural elements.

We need to know the magnitude of the forces that act on a structure.

It is also important to know the mechanical properties of the materials that compose the structure.

For example, if you use rubber as a material, then we can predict that the elements of the structure will lose their shape under a small force