Principles of Structural Analysis and Design – Key Terms

Question-and-answer flashcards covering key definitions, properties, and concepts from structural analysis and design lecture notes.

What is the retarding force that acts opposite the direction of a body in motion?

Kinetic friction

Which structural member has an unsupported height at least three times its least lateral dimension and primarily carries axial load?

Column

What force determines whether a body remains in equilibrium or experiences changing motion?

Resultant force

Which principle states that stress is proportional to strain within the elastic limit?

Hooke’s Law

What constant equals the ratio of lateral strain to longitudinal strain in axially loaded members?

Poisson’s ratio

Which modulus is the constant of proportionality between stress and strain in the elastic range?

Young’s Modulus (Elastic Modulus)

What term refers to the force generated by a body at rest?

Static force

What term refers to the force generated by a body in motion?

Dynamic force

What is the stress value beyond which stress ceases to be proportional to strain?

Proportional limit

How are materials called that have identical composition at every point?

Homogeneous materials

Which property enables a material to undergo large permanent strains before failure?

Ductility

What material property describes the ability to absorb energy in the plastic range?

Toughness

Which property makes a material return to its original dimensions when the load is removed?

Elasticity

What property describes the ability to absorb energy in the elastic range?

Resilience

What term describes stressing high-strength steel tendons before concrete hardens?

Pre-tensioning

What term describes stressing high-strength steel tendons after concrete has gained adequate strength?

Post-tensioning

What is the time-dependent loss of stress in prestressing steel held at constant strain called?

Relaxation

What type of composite material shows different elastic properties in perpendicular directions?

Orthotropic material

What type of material has identical elastic properties in all directions?

Isotropic material

Through which point does the resultant of resistance to applied lateral forces act?

Center of rigidity

What is the distance between the center of mass and the center of rigidity called?

Eccentricity

What physical quantity is measured by a seismometer?

Ground (actual) displacement

The flexibility of a structure is the reciprocal of which quantity?

Stiffness

What do you call a story whose lateral stiffness is less than 70 % of that of the story above?

Soft story

What term denotes the lateral displacement of one level relative to the level above or below?

Story drift

How is liquefaction best described?

A sudden drop in the shear strength of soil

The rigidity of a structure equals the reciprocal of what deformation quantity?

Deflection

Through which point is the seismic force assumed to act?

Center of mass

Which earthquake parameter is measured using the Richter scale?

Magnitude of the earthquake

What term specifies earthquake depth beneath the epicenter?

Focal depth (hypocenter depth)

When the centers of mass and rigidity do not coincide, what additional shear develops?

Torsional shear stress

What failure mechanism occurs in members subjected to many cycles of stress?

Fatigue

What time-dependent deformation under sustained load can lead to sudden fracture?

Creep

What behavior describes continued deformation under minimal load after permanent set has occurred?

Plasticity

What phenomenon is large-amplitude vibration of a system excited at its natural frequency?

Resonance

Which term denotes the highest ordinate on a stress–strain diagram?

Ultimate (rupture) strength

Which term describes appreciable elongation or yielding without corresponding increase in load?

Yield strength