Forms and Function
Internal and External Forces
Internal
shear
tears the structure
in opposite parallel
directions
torsion
twists structure
tension and
compression
when too many
books are placed
on a shelf the shelf
bends resulting in
tension and compression
Compression
squashes structures
resulting in decreased
length
Tension
stretches structures
resulting in increased
length
External
dead loads
the weight of the materials
used to build the structure
live loads
objects on or
within structure
impact forces
strong winds
affect structure
from outside
Stability and Center of Gravity
Center of Gravity
unstable structures like the
tower of pisa's center of gravity
is inside but not centered over
the support base
stable structures can have
their center of gravity
outside or not centered
over the support base
Stability
a stable structure can support
a live load and the support
base/points are not altered
a structure can become
unstable if it can not support
the live load
a chair may become unstable
if a chair leg is lifted above the
ground
Design Features
Joints
rigid joints
prevent movement
mobile joints
allow movement
any place where pieces
are held together
Material
composite materials are
using two different materials
to use both benifits
chosen based on strength
needed, environment etc
Shape
triangular shapes
are strong
corrugations increase
strength in structure
used to spread force
made to
withstand forces
Function
may need to support
humans, support wind etc
consider location
what the structure
is supposed to do
Types of Structures
Shell
egg cartons, food cans, pipes
little building material
strong, hollow
Frame
homes, snowshoes
lightweight designs need
to be fastened to ground
skeleton of strong material
Mass
snow sculptures,
dams, mountains
held in place
by own weight
built by piling
materials
