|Topics||Bridge Forms, Force Lines of Action, Modulus of Elasticity, Specific Gravity|
The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.
Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.
The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).
Specific gravity is the ratio of the density of equal volumes of a substance and water and is measured by a hyrdometer.