Structures

Defining a structure…

A structure usually refers to any large, man-made object permanently fixed to Earth's surface, as a result of construction

A structure is something that can support a load whilst also supporting its own mass

What types of

structures are there?

Mass – solid structure that use their own weight to resist loads

Frame – built using small parts(members) to form a larger structure

Shell – hollow structures made in one piece e.g. cans, footballs,Aeroplanes, cars.

This climbing frame was made out of metal piping and can easily support its own weight and that of the children.

This type of structure is known as a frame structure.This is because it is made from many parts which

are called members.

The members are joined together to create a rigid structure.

A beam is the name given to a member that is supported at either end by a column.

What is meant by force? In physics, a force is that which can cause an object with mass to

accelerate. Such as lift, push and pull.

Forces are acting on all objects in the world at any time. If they are stationary or moving.

These two forces are divided into two subcategories, static (stationary), and dynamic (moving).

Static Force Static force is usually the force that allows the structure to be able to hold

its own weight and not collapse when stationary.

This structure is supporting its own weight and hasn’t collapsed!

Dynamic Force Dynamic force is usually the force that allows the structure to be able to

hold both its own weight and extra from the users and not collapse when in use.

The structure is now supporting both its own weight and that of the users

How can we calculate force?

Force (recorded in Newton's ‘N’) is expressed as;mass (kg) x acceleration (m/s2)

(N= m x a)

E.g.

Static swing + child = 50kg x 0m/s = 50N

Moving swing + child = 50kg x 3m/s = 150

Triangulation Frame structures are often triangulated to create a strong structure.

Triangulation is a method of allowing force to disperse evenly throughout the structure and give the most strength for the least mass. Some examples are shown below:-

Struts and Ties

A STRUT is the name given to the part of the structure which is subject to compression (it is being squashed).

A TIE is the name given to the part of the structure which is subject to tension (it is being stretched).

What struts and ties can you see in these pictures?

Compression & Bending

This climbing frame is under compression due to the weight being exerted on it by the users(purple arrow). A compression effect has been applied to the top beam that supports the swings.

The beams are also subject to a bending effect as the wooden beams are being both squashed (purple arrow) on the top and stretched (yellow arrow) on their underside, at the same time.

What other features are under compression?