PSAD TERMS 1

Resultant

is the force which determines whether the body will be in equilibrium or will have a varying state of motion.

Hooke's Law

states that the stress is proportional to the strain within the elastic region.

Poisson's Ratio

states that in the deformation of axially loaded members, the ratio of the lateral to the longitudinal strain is constant.

Young's Modulus (Modulus of Elasticity)

within the elastic range, it is the constant of proportionality that defines the linear relationship between stress and strain.

Isotropic Materials

are materials whose properties remain the same when tested in different directions.

Anisotropic Materials

are materials that display varying properties when tested in different directions.

Orthotropic Materials

are materials whose mechanical or thermal properties are unique and independent in three mutually perpendicular directions.

Homogeneous Materials

are materials of uniform composition throughout that cannot be mechanically disjointed, in principle, into different materials.

Prismatic Material

materials whose cross-section are the same at any location across its longitudinal axis.

Column

is a structural member that has the ratio of its unsupported height to its least lateral dimension of not less than 3 and is used primarily to support axial load.

Kinetic friction

is the retarding force acting opposite a body in motion.

Fault Line

A fracture plane in the earth's crust across which relative displacement has occurred.

Dip Angle

The current dip or dip angle is the angle of a formation referenced from the horizontal plane.

Ground Displacement

Is how far the surface moves during the earthquake. It is measured by a seismometer.

Seismograph

are instruments used to record the motion of the ground during an earthquake.

Ritcher scale

a quantitative measure of an earthquake's magnitude.

Proportional Limit

is the term for the value beyond which the stress is no longer proportional to the strain.

Concrete

is a mixture of cementitious material, aggregate, and water. and

Cement Slump Test

measures the consistency of fresh concrete before it sets.

Water-Cement Ratio

is the single most important factor governing the strength and durability of concrete.

Yielding

A material condition that causes it to deform permanently even due to slight increase of stress.

Fatigue

is caused when a material is subjected to repeated cycle of stress or strain.

Creep

when a material is loaded over a long period, it causes it to deform continuously until failure.

Plasticity

is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces.

Frequency (of a wave)

refers to the number of waves that pass through a point in one second.

Period

is the amount it takes one wave cycle to pass the given point.

Resonance

is the tendency of a system to oscillate with greater amplitude at some frequencies at others.

Resonance frequency (of a given system)

is the frequency at which the maximum-amplitude oscillation occurs.

Pre-tensioning

stressing high strength steel wires before concrete hardens.

Post-tensioning

stressing high strength steel after the concrete has been cast and has attained sufficient strength.

Relaxation

the loss of stress that takes place with the passage of time as concrete is held at a constant strain.

Accidental eccentricity

is aimed to account for any unforeseen factor that may attribute to the torsional response.

Out-of-plane offset irregularity

refers to the fact that the vertical members bearing horizontal force are located on another axis rather than its own axis continuing along the height of the structure.

Story drift

is the lateral displacement of one level relative to the level above or below.

Ductility

is a mechanical property of a material that describes its ability to deform under tensile stress without fracturing

Brittleness

refers to a material's tendency to fracture or break without significant deformation.

Toughness

is a mechanical property of a material that refers to its ability to absorb energy without fracturing.

Resilience

is a mechanical property of a material that describes its ability to absorb and store elastic energy when deformed and then release that energy upon unloading.

Elasticity

is a fundamental mechanical property of a material that describes its ability to deform under applied stress and return to its shape and size when the stress is removed.

Stiffness

refers to the ability of a material to resist deformation when subjected to an applied load or force.

Malleability

is the ability of a material to undergo large permanent deformation in compression or property which enables a material to be beaten or rolled into thin sheets.

Center of rigidity

it is the point through which the resultant of the resilience to the applied force acts.

Center of mass

it is the point through which the applied seismic force acts.

Eccentricity

it is the distance between the center of rigidity and center of mass.

Torsional shear stress

it occurs when the structure's center of mass does not coincide with its center of rigidity.

Soft story irregularity

is the irregularity in which the lateral stiffness of a story is less than 70 percent of the stiffness of the story above.

Liquefaction

is a sudden drop in the shear strength of a soil.

Rigidity

is the reciprocal of deflection.

Focal depth

besides the epicenter, it describes the location of earthquake.

Damping

the dissipation of energy from an oscillating system, primarily through friction.

Rupture strength

is the stress at failure.

Ultimate strength

is the highest ordinate in stress-strain diagram.

Yield strength

is an appreciable elongation or yielding of the material without any corresponding increase of load.