Structural Engineering & Reinforced Concrete Review

Comprehensive vocabulary flashcards covering structural properties, mechanics of materials, beam and column behavior, seismic design provisions, and reinforced concrete terminology.

Magnitude

The amount of force, expressed in Newtons ($N$).

Direction

The orientation of the path or line of action of a force, usually described by the angle that the line of action makes with a reference line.

Sense

The manner in which a force acts along its line of action.

Coplanar Force System

A force system where all forces act within a single plane, such as that of a vertical wall.

Concurrent Force System

A force system in which the lines of action of all forces intersect at a common point.

Moment

The product of force and distance ($\text{force} \times \text{distance}$) acting about a specific point called the center of moment.

Moment Arm

The shortest or perpendicular distance from the center of moment to the line of action of the force.

Stress-Strain Diagram

A graphic representation of the relationship between unit stress values and the corresponding unit strains for a specific material.

Proportional Limit

The highest unit stress for which the deformation of a body is proportional to the stress, or the maximum stress at which the material springs back to its original length when the load is released.

Elastic Limit

The maximum stress below which a material does not return to its original length but incurs a permanent deformation called permanent set.

Yield Point

The stress level at which deformation increases without any increase in the load, during which the material exhibits a decrease in cross section at some portion.

Ultimate Strength

The maximum stress that can be attained immediately before actual failure or rupture occurs.

Allowable Stress

The maximum unit stress permitted for a material in the design of a structural member, usually a fraction of its elastic limit, yield strength, or ultimate strength (also called working stress).

Brittleness

The property of a material that causes it to rupture suddenly under stress with little evident deformation, lacking plastic behavior and giving no warning of impending failure.

Ductility

The property of a material that enables it to undergo plastic deformation after being stressed beyond the elastic limit and before rupturing.

Elasticity

The property of a material that enables it to deform in response to an applied force and recover its original size and shape upon removal of the force.

Toughness

The property of a material that enables it to absorb energy before rupturing, represented by the area under the stress-strain curve derived from a tensile test.

Modulus of Elasticity

A coefficient expressing the ratio between unit stress and corresponding unit strain below the proportional limit, represented by the slope of the straight-line portion of the stress-strain diagram.

Permanent Set

The inelastic strain remaining in a material after complete release of the stress producing the deformation.

Yield Strength

The stress necessary to produce a specific limiting permanent set in a material, usually $0.2\%$ of its original length when tested in tension.

Creep

The gradual permanent deformation of a body produced by the continued application of stress or prolonged exposure to heat over time.

Fatigue

The weakening or failure of a material at a stress below the elastic limit when subjected to repeated cycles of stress.

Axial Force

A tensile or compressive force acting along the longitudinal axis of a structural member and at the centroid of the cross section, producing axial stress without bending, torsion, or shear.

Eccentric Force

A force applied parallel to the longitudinal axis of a structural member but not at the centroid of the cross section, producing bending and uneven stress distribution.

Poisson's Ratio

The ratio of lateral strain to the corresponding longitudinal strain in an elastic body subjected to longitudinal stress.

Shearing Stress

The force per unit area developed along a section of an elastic body to resist a shear force (also called shear stress or tangential stress).

Torsion

The twisting of an elastic body about its longitudinal axis caused by two equal and opposite torques, producing shearing stresses in the body.

Effective Depth of Section ($d$)

The depth of a concrete section measured from the extreme compression fiber to the centroid of the tension reinforcement.

Concrete Cover

The amount of concrete required to protect steel reinforcement from fire and corrosion, measured from the surface of the reinforcement to the outer surface of the concrete section.

Balanced Section

A reinforced concrete section in which the tension reinforcement theoretically reaches its specified yield strength at the same time the concrete in compression reaches its assumed ultimate strain.

Overreinforced Section

A concrete section in which the concrete in compression reaches its assumed ultimate strain before the tension reinforcement reaches its specified yield strength, leading to sudden failure without warning.

Underreinforced Section

A concrete section in which the tension reinforcement reaches its specified yield strength before the concrete in compression reaches its assumed ultimate strain, resulting in ductile failure with prior warning.

Neutral Axis

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

Camber

A slight convex curvature intentionally built into a beam, girder, or truss to compensate for anticipated deflection.

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, indicating cross-sectional distribution.

Section Modulus

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

Inflection Point

A point at which a structure changes curvature from convex to concave or vice versa under transverse load, characterized by a bending moment of zero.

Continuous Beam

A beam extending over more than two supports in order to develop greater rigidity and smaller moments than a series of simple beams.

Buckling

The sudden lateral or torsional instability of a slender structural member induced by the action of an axial compressive load.

Critical Buckling Load

The maximum axial load that can theoretically be applied to a column without causing it to buckle (also called Euler buckling load).

Slenderness Ratio

The ratio of the effective length of a column to its least radius of gyration ($L_e / r$).

Radius of Gyration

The radial distance from an axis at which the mass of a body could be concentrated without altering its moment of inertia, equal to $\sqrt{I / A}$.

P-Delta Effect

An additional secondary moment developed in a structural member as its longitudinal axis deviates from the line of action of a compressive load, equal to the load multiplied by the lateral deflection.

Middle Third Rule

The proposition that a compressive load should be located within the middle third of a horizontal cross section of a column or wall to prevent tensile stresses from developing.

Kern

The central area of any horizontal section of a column or wall within which the resultant of all compressive loads must pass to prevent tensile stresses from developing.

Effective Length Factor

A coefficient modifying the actual length of a column according to its end conditions to determine its effective length.

Accelerograph

An instrument that measures the velocity and acceleration of ground motion during an earthquake.

Caisson

A watertight cylindrical or rectangular chamber used in underwater construction to protect workers from water pressure and soil collapse.

Coffer Dam

A temporary watertight enclosure or dam-like structure constructed to exclude water from a foundation site during excavation and construction.

Diaphragm

A horizontal or nearly horizontal structural system, including horizontal bracing, that acts to transmit lateral forces to vertical resisting elements.

Diaphragm Strut

A structural member of a horizontal bracing system parallel to the applied load that takes axial tension or compression and transfers shear to vertical resisting elements.

Gunite

A rich cement mortar applied to surfaces by spraying under high compressed air pressure.

Base Shear

The total designed lateral force or shear acting at the base level of a structure.

Soft Storey

A storey whose lateral stiffness is less than $70\%$ of the stiffness of the storey directly above it.

Weak Storey

A storey whose lateral strength is less than $80\%$ of the strength of the storey directly above it.

Development Length

The length of embedded reinforcement required to develop the design strength of the reinforcing bar at a critical section.

Wobble Friction

The friction caused by the unintended deviation of a prestressing sheath or duct from its specified profile in prestressed concrete.

Stirrup

Lateral reinforcement used to resist shear and diagonal tension stresses in a flexural structural member.