Cantilever:  A beam or other projection that is supported at only one end and projects beyond.

  • A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress.  Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs. This is in contrast to a simply supported beam such as those found in a post and lintel system. A simply supported beam is supported at both ends with loads applied between the supports.
  • Cantilevers are widely found in construction, notably in cantilever bridges and balconies (see corbel). In cantilever bridges the cantilevers are usually built as pairs, with each cantilever used to support one side of a central section.

Beam:  A beam is a horizontal structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.

  • Beams are traditionally descriptions of building or civil engineering structural elements, but smaller structures such as truck or automobile frames, machine frames, and other mechanical or structural systems contain beam structures that are designed and analyzed in a similar fashion.
  • A squared-off log or a large, oblong piece of timber, metal, or stone used especially as a horizontal support in construction.
  • Nautical: A transverse structural member of a ship’s frame, used to support a deck and to brace the sides against stress.

Moment of force (often just moment) is the tendency of a force to twist or rotate an object; see torque for details. This is an important, basic concept in engineering and physics.

  • The moment arm is the perpendicular distance from the point of rotation, to the line of action of the force.
  • The moment may be thought of as a measure of the tendency of the force to cause rotation about an imaginary axis through a point.
  • Note: In mechanical and civil engineering, “moment” and “torque” have different meanings, while in physics they are synonyms.

Torque: Torque, moment or moment of force is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object.

  • Loosely speaking, torque is a measure of the turning force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.
  • The magnitude of torque depends on three quantities: the force applied, the length of the lever arm connecting the axis to the point of force application, and the angle between the force vector and the lever arm. 

A shear stress, is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section. Normal stress, on the other hand, arises from the force vector component perpendicular or antiparallel to the material cross section on which it acts.

  • noun Physic.  the external force acting on an object or surface parallel to the slope or plane in which it lies; the stress tending to produce shear.
  • Force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress. The resultant shear is of great importance in nature, being intimately related to the downslope movement of earth materials and to earthquakes. Shear stress may occur in solids or liquids; in the latter it is related to fluid viscosity.

Post and lintel:  a structure consisting of vertical beams (posts) supporting a horizontal beam (lintel)

  • Whew! Finally an easy one!!
  • The simplest illustration of load and support in construction is the post-and-lintel system, in which two upright members (posts, columns, piers) hold up a third member (lintel, beam, girder, rafter) laid horizontally across their top surfaces. This is the basis for the evolution of all openings. But, in its pure form, the post-and-lintel is seen only in colonnades and in framed structures, since the posts of doors, windows, ceilings, and roofs are part of the wall.
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