DK CHING: BEAM

Beam

Rigid structural member designed to CARRY AND TRANFER TRANSVERSE LOADS across space to supporting elements

Span

Extent of space BETWEEN two support

Clear span

Distance between the INNER FACES of the supports of span

Effective span

CENTER TO CENTER DISTANCE between the supports of a span

Bending moment

External moment, causing part of the structure to ROTATE OR BEND

Resisting moment

Internal moment equal and opposite to a Bending Moment, generated by force couple to MAINTAIN EQUILIBRIUM. Opposite of bending moment

Deflection

Perpendicular distance a spanning member deviates from a true course under transverse loading

Camber

SLIGHT CONVEX curvature intentionally built into a beam, girder or truss to COMPENSATE FOR AN ANTICIPATED DEFLECTION

Transverse shear

A shear force at a cross section of a beam or other member subject to bending, equal to the algebraic sum of transverse forces on one side of section.

Horizontal shearing stress

The shearing stress developed to prevent slippage along horizontal planes of a beam under transverse loading, equal at any point to the vertical shearing stress at that point.

Vertical shearing stress

The shearing stress developed along a cross section of a beam to resist transverse shear, having a maximum value at the neutral axis and decreasing nonlinearly toward the outer faces.

Bending stress

A combination of compressive and tensile stresses developed at a cross section of a structural member to resist a transverse force, having a maximum value at the surface furthest from the neutral axis.

Neutral axis

An imaginary line passing through the centroid of the cross section of a beam or other member subject to bending, along which no bending stresses occur.

Flexure formula

A formula defining the relationship between bending moment, bending stress, and the cross-sectional properties of a beam.

Moment of inertia

The sum of the products of each element of an area and the square of its distance from a coplanar axis of rotation.

Section modulus

A geometric property of a cross section, defined as the moment of inertia of the section divided by the distance from the neutral axis to the most remote surface.

Lateral buckling

The buckling of a structural member induced by compressive stresses acting on a slender portion insufficiently rigid in the lateral direction.

Principal stresses

The tensile and compressive stresses resulting from the interaction of bending and shear stresses at a cross section of a beam.

Stress trajectories

Lines depicting the direction but not the magnitude of the principal stresses in a beam.

Shear center

The point in the cross-sectional plane of a structural member through which a transverse load must pass in order to prevent torsion or twisting of the member about a longitudinal axis.

Shear diagram

A graphic representation of the variation in magnitude of the external shears present in a structure for a given set of transverse loads and support conditions.

Moment diagram

A graphic representation of the variation in magnitude of the bending moments present in a structure for a given set of transverse loads and support conditions.

Cantilever

Beam or rigid structural member extending beyond the fulcrum.

A rigid structural element that extends horizontally and is supported at only one end.

Positive shear

A net resultant of shear forces that acts vertically upward on the left part of the structure being considered.

Negative shear

A net resultant of shear forces that acts vertically downward on the left part of the structure being considered.

Positive moment

A bending moment that produces a concave curvature at a section of a structure.

Inflection point

A point at which a structure changes curvature from convex to concave or vice versa as it deflects under a transverse load, theoretically, an internal hinge and therefore a point of zero moment.

Negative moment

A bending moment that produces a convex curvature at a section of a structure.

Haunch

The part of a beam that is thickened or deepened to develop greater moment resistance.

Suspended-span

A simple beam supported by the cantilevers of two adjoining spans with pinned construction joints at points of zero moment.

Effective length

The distance between inflection points in the span of a fixed-end or continuous beam, equivalent in nature to the actual length of a simply supported beam.

Simple beam

A beam resting on a simple supports at both ends, which are free to rotate and have no moment resistance. As with any statically determinate structure, the values of all reactions, shears, and moments for a simple beam are independent of its cross-sectional shape and material.

Cantilever beam

A projecting beam supported at only one fixed end.

Overhanging beam

Beam EXTENDING BEYOND ITS SUPPORT

Double overhanging beam

Beam extending beyond BOTH of its supports

Fixed end beam

Beam having BOTH ENDS restrained against TRANSLATION AND ROTATION

Continuous beam

A beam extending over more than two supports in order to develop greater rigidly and smaller moments than a series of simple beams having similar spans and loading.