PSAD STRUCTURAL

Surface forces

are caused by the direct contact of one body with the surface of another.

body force

is developed when one body exerts a force on another body without direct

physical

contact between

the

bodies.

Prismatic

All cross sections are the same throughout its length.

Homogeneous material

has the same physical and mechanical properties throughout its volume.

Isotropic material

has these same properties in all directions

Load Factors

reflect the probability that the total loading R will occur for all the events stated.

Resistance factor

(Ф) are determined from the probability of material failure as it relates to the material's quality and the consistency of its strength.

shear strain

If we select two line segments that are originally perpendicular to one another, then the change in angle that occurs between them is referred to as

yielding

A slight increase in stress above the elastic limit will result in breakdown of the material and cause it to deform permanently. This behavior is called

the yield stress or yield point

plastic deformation

The stress that causes yielding is called _______, or , and the deformation that occurs is called _______

Strain Hardening.

When yielding has ended, an increase in load can be supported by the specimen, resulting in a curve that rises continuously but becomes flatter until it reaches a maximum stress referred to as the ultimate stress.

Necking

Up to the ultimate stress, as the specimen elongates, its cross-sectional area will decrease.

Ductile Materials.

Any material that can be subjected to large strains before it fractures is called a ductile material.

Brittle Materials

Materials that exhibit little or no yielding before failure are referred to as brittle materials.

strain energy.

As a material is deformed by an external load, the load will do external work, which in turn will be stored in the material internal energy. This energy is related to the strains in the material, and so it is referred to as

Modulus of Resilience

When the stress reaches the proportional limit, the strain-energy density is referred to as the modulus of resilience.

Modulus of toughness

This quantity represents the entire area under the stress-strain diagram, and therefore it indicates the maximum amount of strain-energy the material can absorb just before it fractures.

Ductility Factor

The ratio of modulus of toughness to the modulus of resilience.

Creep

When a material has to support a load for a very long period of time, it may continue to deform until a sudden fracture occurs or its usefulness is impaired.

Fatigue

When a metal is subjected to repeated cycles of stress or strain, it causes its structure to break down, ultimately leading to fracture.

Plasticity

A condition where a material break down and deforms permanently even due to a slight increase in stress above the elastic limit.

Residual Stress

When the plastic moment is removed from the beam then it will cause residual stress to be developed in the beam

Beams

Members that are slender and support loadings that are applied perpendicular to their longitudinal axis.

Dilatation

The change in volume per unit volume is called the “volumetric strain”or the dilatation.

Resonance

It occurs when a building period coincides with the earthquake period.

Torsional Shear Stress.

Occurs when the structures center of mass does not coincide with the center of rigidity.

Ground Displacement.

Measured by a seismometer.

Rigidity of a Structure

Reciprocal of deflection

Story

It is the space between two adjacent floors.

Diaphragms

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

Shear wall

Wall designed to resist lateral forces acting on its own plane, typically wind and seismic loads.

Center of Gravity

It is the point where the object “suffers” no torque by the effect of the gravitational force acted upon it.

Center of Rigidity

It is point through which the resultant of the resistance to the applied lateral force acts.

Center of Mass

It is point through which the applied seismic force acts.

Eccentricity

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

Design seismic base shear.

It is the total design lateral force

Flexibility of a structure.

Inverse of stiffness.

Story drift

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

Story displacement

Lateral displacement of the story relative to the base.

Damping

Rate at which natural vibration is absorbed.

Seismometer

Instrument use to measure the peak ground acceleration, which is one of the most important characteristics of an earthquake.

Magnetometer

Instrument use to measure the strain of rock under pressure

Focus (Hypocenter)

The originating earthquake source of the elastic waves inside the earth which cause shaking of ground due to earthquakes

Epicenter.

The point on the earth’s surface directly above the focus

Story drift ratio

Story drift divided by the story height.

Intensity

A measure of the strength of shaking during earthquake.

Magnitude. A measure of energy released in

an earthquake.Imo