Lecture Notes: Structural Engineering and Seismic Concepts (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and their definitions from Structural Engineering, materials, and seismic terminology.

Statics

Branch of mechanics which studies the effects and distribution of forces on rigid bodies that are at rest.

Friction

Contact resistance by one body when the second body moves or tends to move past the first body.

Strain energy

Energy stored in a material due to its deformation.

Modulus of toughness

The maximum amount of strain-energy a material can absorb just before it fractures (energy absorption in the plastic range).

Modulus of resilience

The largest amount of internal strain energy per unit volume a material can absorb without permanent damage (energy absorption in the elastic range).

Elasticity

Property of a material to return to its original dimensions when the load is removed.

Ductility

Ability of a material to deform in the plastic range without breaking.

Stiffness

Ability to resist deformation within the linear range (inverse is flexibility).

Toughness

Material’s resistance to fracture.

Hardness

Material’s resistance to indentation.

Ductile materials

Materials that can undergo large strains before fracture.

Brittle materials

Materials that exhibit little or no yielding before failure.

Homogeneous material

Material with the same physical and mechanical properties throughout its volume.

Isotropic material

Material with the same physical and mechanical properties in all directions.

Orthotropic material

Material properties differ along three mutually orthogonal axes.

Prismatic

All cross sections are the same throughout the length.

Creep

Time-dependent permanent deformation under sustained load, potentially leading to fracture.

Fatigue

Failure due to repeated cycles of stress or strain.

Buckling

Lateral deflection of long slender members under axial compression.

Yielding

Permanent deformation that begins when stress exceeds the elastic limit (plastic deformation).

Strain hardening

Post-yielding increase in load to reach ultimate stress.

Necking

Localized reduction in cross-sectional area after ultimate stress leading to fracture.

Concrete

A mixture of water, cement, sand, gravel/crushed rock, or other aggregates.

Aggregates

Materials used in concrete; can be fine or coarse.

Fine aggregates

Aggregates passing through a No. 4 sieve.

Water (in concrete)

Clean water free from injurious oils, acids, alkalis, salts, and deleterious substances.

Actual displacement

Displacement measured by a seismometer.

Center of rigidity

Point through which the resultant resistance to the applied lateral force acts.

Center of gravity

Point where gravity produces no net torque.

Center of mass

Point through which the applied seismic force acts.

Center of stiffness

Point through which the resultant of the restoring forces acts.

Column

Structural member with height-to-least-dimension ratio ≥ 3, primarily supporting axial load.

Corbel

Short edge beam projecting from a column to support weight.

Damping

Adding energy-absorbing components to a frame to reduce lateral deflections and stresses from wind or seismic forces.

Design seismic base shear

Total design lateral force at the base of a structure.

Elasticity

Property of a material to return to its original shape after loading is removed.

Eccentricity

Distance between the center of rigidity and the center of mass.

Epicenter

Geographic point on the Earth's surface directly above the earthquake focus.

Focus

Originating earthquake source of seismic waves inside the Earth.

Focal depth

Depth location of the earthquake focus, besides the epicenter.

Homogeneous

Material with the same composition throughout.

Hooke’s Law

Stress is proportional to strain in the elastic region.

Kinetic friction

Frictional force opposing motion between moving surfaces.

Liquefaction

Soil state where shear strength drops dramatically under saturation, making soil behave like a fluid.

Magnitude (earthquake)

Measure of energy released, often assessed on a logarithmic scale (e.g., Richter scale).

Orthotropic

Composite material with different elastic properties along different directions.

Poisson’s ratio

Ratio of lateral to axial strain in a material under load.

Post-tensioning

Stressing high-strength steel after concrete has gained sufficient strength.

Pre-tensioning

Stressing high-strength steel before concrete hardens.

Proportional limit

Value beyond which stress is no longer proportional to strain.

Elastic limit

Greatest stress that can be applied without permanent elongation upon unloading.

Modulus of elasticity

Slope of the elastic portion of the stress-strain curve; stress divided by strain.

Plasticity

Permanent deformation continues under load beyond the elastic region.

Reciprocal of deflection

Rigidity of a structure (inverse concept of deflection).

Reciprocal of stiffness

Flexibility of a structure (inverse of stiffness).

Relaxation

Loss of stress with time when concrete is held at constant strain.

Resilience (material property)

Ability to absorb energy in the elastic range.

Resonance

Large amplitude vibration when a structure’s natural period matches the earthquake period.

Natural period

Time period of undamped free vibration of a structure.

Intensity

Measure of shaking strength based on observed effects and damage.

Magnitude

Measure of energy released by an earthquake.

Seismographs

Instruments that record ground motion during earthquakes.

Soft storey

Storey with lateral stiffness less than 70% of the storey above (or <80% of the three storeys above).

Weak storey

Storey with lateral strength less than 80% of the storey above.

Resultant

Determines whether a body is in equilibrium or in motion.

Static

Force associated with bodies at rest.

Story drift

Displacement of one level relative to the level above or below.

Story

Space between two adjacent floors.

Story displacement

Lateral displacement of a story relative to the base.

Out-of-plane offsets

Discontinuities in a lateral force path.

Diaphragms

Rigid horizontal planes that transfer lateral forces to vertical resisting elements.

Shear wall

Wall designed to resist lateral forces in its own plane; transfers forces to foundation.

Torsional shear stress

Stress from misalignment of the center of mass and rigidity.

Yielding

Permanent deformation with a slight increase in stress.

Yield stress

Stress at which marked strain occurs without an increase in stress.

Ultimate stress

Maximum stress a material can develop.

Rupture strength

Stress at which the specimen actually breaks.

Water–cement ratio

Significantly influences concrete quality and strength.

Young’s modulus

Proportionality constant between stress and strain in the elastic region.

Factor of safety

Ratio of failure stress to allowable stress.

Failure

Condition where a load-resisting member can no longer resist further load increases.

Diagonal tension

Tensile stress that develops on the diagonal surface.

Poisson’s ratio (redundant)

Ratio of lateral to axial strain in an unrestrained member.

Dilatation

Change in volume per unit volume.

Ductile material

Material that exhibits large tensile strain up to rupture.

Brittle material

Material that exhibits little plastic deformation before rupture.

Tangent modulus

Rate of change of stress with respect to strain.

Specific strength

Ratio of ultimate or tensile strength to the material’s specific weight.

Deflection

Displacement of a point in a structure under load (rigidity-related concept).

Reciprocal of Deflection (clarified)

Another way to express rigidity of a structure.

Specific modulus

Ratio of Young’s modulus to the specific weight.

Isotropic material (redundant)

Material with identical elastic properties in all directions.

Seismograph (redundant)

Ground-mounted device measuring actual ground displacement.

Dynamic

Forces generated by motion of a body.

Anisotropic

Materials whose properties depend on the direction considered.

Corrosion

Failure of a metal due to repeated stress.

Camber

Built-in upward curvature of a beam or girder to compensate for deflection or sag.

Full sinewave

Buckling shape that a member may take under certain conditions, resembling a sine wave.

Workability

The ease of placing, consolidating, and finishing concrete.

Plastic Hinge

A deformation of part of a beam where plastic bending occurs.