|
|
|
There
are forces pushing, pulling and twisting every structure.
Some of these forces are created by what we do with a structure,
such as walking over a bridge or sitting on a chair. Some
forces are there all the time
|
|
Docklands Railway station
suspension footbridge. |
|
Docklands Railway station
suspension footbridge. |
|
A
load is simply the amount of push
or pull. A structure
has to be designed so that it will carry the amount of load
it needs to when the structure is used
|
|
|
A
designer works out the loads so that the structure will not
collapse. For instance a bridge has to withstand:
|
|
Docklands Railway station
suspension bridge detail. |
|
Load from its own weight
Load from things crossing it
Load from winds pushing against it
|
Millennium Dome, cranes
& bridge. |
|
Another
example would be a chair. The load on the chair could be worked
out and the chair could be made and tested so that the designer
is sure that it will not collapse when used.
|
|
|
When
we design and make a structure, we need to make sure that
the loads are spread,
or distributed
through the parts. All of the parts of the structure are known
as members.
Each of them helps to distribute the load so that no part
is under too much strain
|
|
Millennium Dome mast detail. |
|
Motorway arch bridge. |
|
For
example, all of the members in a bridge take the load and
allow it to pass to the ground on each side of the place that
the bridge crosses.
|
|
|
In
all structures, the designer tries to balance
the forces so that they are even. If they are not,
the structure is likely to collapse
or fail
|
|
Tacoma Bridge collapse.
|
|
|
|
|
For instance, if there is a lot more load on one end of a
see-saw, it will tip up. If the load is the same at both ends
it will be balanced
or in equilibrium
|
|
|
|
|
|
|
|
|
|
|
|
|
