for use with materialworlds Bridge simulation
© materialworlds.com 2002
1. Arch bridges
a) What are the forces between the bricks in a bridge - and how do they keep the bridge standing?
b) How do these forces change when the bridge is under load? (try dropping the brick or just pull the bridge with the mouse)
c) What difference does the curvature of the bridge make to the forces within it?
d) What forces do the bridge foundations need to be able to resist - and how are these affected by the curvature of the bridge?
2. Beam bridges
These bridges are made up of balls joined by elastic links. When the links are compressed they are drawn in red - or yellow under greater compression. Under tension the supports are drawn in blue.
a) What are the forces (compression or tension) in different parts of the bridge - and how do they keep the bridge standing?
b) How do these forces change when the bridge is under load? (try dropping the brick or just pull the bridge with the mouse)
c) How do the short and long bridges (but same thickness) differ in their behaviour?
d) What forces do the bridges exert on their supports?
d) What changes would you make to improve the long beam bridge?
3. Arch and beam bridge comparison
a) How are the ways that arch and beam bridges support themselves different?
b) How does this affect the choice of material you could use to construct the different types of bridge?
4. Bridge foundations
a) How do the forces the two types of bridges exert on their foundations differ (under normal bridge loads) ?
The fixed supports of the bridges are shown with cross-hatching. In these simulations the supports don't move in response to the forces of the bridge upon them.
b) What exactly would happen - in the case of the differents bridge types - if the support foundations weren't entirely solid?
c) How would you try to ensure in reality that the supports of real bridges didn't move?
About the simulations:
The beam bridges are made up of balls joined by elastic links. As the links become compressed they are drawn in red - or yellow under greater compression. Under tension the supports are drawn in blue.
The arched bridges are made of composite interlocking bricks.
Both simulations use materials that are much more elastic than would be used for real bridges - magnifying (and making more visible) their displacements and movements.
The fixed supports of the bridges are shown with cross-hatching.
Red arrows show forces on an object. Thin headed arrows show the individual forces that combine together to give the triangle headed resultant force.
Blue arrows show the direction and speed of an object's velocity.
The longer an arrow, the greater the force and velocity it represents.
Force and velocity arrows aren't shown by default in the beam bridges, as they could hide the link color - but you can switch them on if you like.
Pressing the
rewind
button returns the simulation to its initial state.