Polymorf - Knowhere - Truss beam

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

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 45^o

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.

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