I-beams
are typically made from steel or from concrete |
 |
that is reinforced with pre-stressed steel rods to improve |
its tensile strength. The top and bottom horizontal parts |
of
the steel I-beam
are called flanges, and the middle, |
vertical section, is called the web. Load bearing
Ι-beams |
are called girders. Another advantage of the
I-beam |
design is that sections can be riveted, bolted, or welded |
together to make longer members and fix them to their |
supports. This enables the creation of extended steel |
Fig. 149 - Steel Ι-beam
skeleton |
Ι-beam
and column skeleton frameworks
for multi-story |
framework of a building |
buildings like skyscrapers. |
(visualization model) |
|
. |
Truss
beams |
. |
There
are limits to how much material can be removed from the middle of an
Ι-beam
and |
placed
at its outer edges before the web becomes too slender for its height and
is prone to |
twisting
and buckling under load. To repeat, the material in the middle of
the beam's |
cross section resists the tendency of the upper and lower edges of the
beam to slide past |
each
other, or shear, when loaded. One design solution is to use a truss
beam where the |
. |
 |
|
Fig. 150 - Truss beam |
(demonstration model) |
click image to enlarge |
|
|
. |
web
consists of a triangulated arrangement of small diameter struts instead of
being one |
continuous section of material. A force applied to the top edge of
the truss beam is |
distributed throughout the struts as axial forces. The diagonal
struts should be angled 45o |
relative
to the flanges of the beam for maximum resistance to shear stresses.
Truss beams |
are
commonly used for floor support joists and rafters in buildings. |
. |
Back to
Knowhere |
 |
Page 98 -
Building stability - Truss beam |
 |
|