Module civil::structural::beams

WIP If this gets unweildy, we might have to break out parts of this module into sections.

Conventions:

The source uses the following standard conventions for refering to variables:

• A = Area
• I = Moment of inertia (m^4)
• S = Section Modulus (m^4)
• E = Modulus of elasticity (kPa)
• c = Distance to extreme fiber (m)
• W = Load (kN)
• L = Length (m)
• R = reaction (kN)
• V = Shear (kN)
• M = Bending moment (N-m)
• a = spacing
• B = major width & b = minor width
• H = major height & h = minor height
• R = outer radius & r = inner radius (used interchangeably with H & h where practical)
• D = deflection

Structs

CircularBeam	A beam with a round, solid cross section Gere, James M., "Mechanics of Materials," 6th Ed.
CircularTube	A beam with a circular cross section with a hollow center. Gere, James M., "Mechanics of Materials," 6th Ed.
IBeam	A beam with an "I" shaped cross section. This includes standard beams "s-beams" and wide-flange beams "w-beams" Gere, James M., "Mechanics of Materials," 6th Ed.
Load	Load represents a non-reactive force applied to a beam. This could be the weight of some object being supported, like another beam a working load or anything else which acts directly on the beam. Loads are defined by three things:
PolygonalBeam	A beam with a solid, regular-polygonal cross section. This would include rectangular beams, and any shape with three or more sides of equal length Gere, James M., "Mechanics of Materials," 6th Ed.
Support
TrapezoidalBeam	A solid beam with a trapezoidal cross section. These are not typically used in common construction practice; however, they could be useful for exploring the behavior of novel building materials. Gere, James M., "Mechanics of Materials," 6th Ed.

Enums

SupportType

Beam supports. Where a beam support does not exist, the beam is implicitly free (unsupported). Otherwise, the beam support is Fixed (a support which can provide a reaction shear and a reaction moment) or the beam is Simple (a support which can provide a reaction shear but not a reaction moment)

Traits

Beam	This trait gives us a common interface to the formulas used for determining the properties of beams which vary with a particular beam cross section.