Why are beams stronger when
they are vertical rather than flat?
What holds a beam
Look at broken beam, sponge, beam model
Force downwards causes compression in top of beam, and tension
in bottom of beam
Downwards force becomes a sideways force, resisted by the tensile strength
of the beam—structural beams have wide flanges to provide extra
material at point of greatest stress, and little material in middle
(web) where forces are minimal
The wider the web, the less the force on the bottom flange.
Beams are efficient
Greek temples had stone posts and beams.
Stone is strong
in compression, but weak in tension- stone lintels easily cracked. So
lots of columns were needed.
Romans developed the arch ( rebuild model ), which transmits the load
to the ground in compression only- can span large distances.
Many beam bridges have a slight arch ( camber) to reduce tension on