Structural Terms 1

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

A 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 factors (𝜙) are determined from the probability of material failure as it relates to the material’s quality and the consistency of its strength.

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

The stress that causes yielding is called the yield stress or yield point,

𝜎𝑌 , and the deformation that occurs is called plastic deformation.

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.

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

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 earthquake.

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.

Liquefaction. Is a state in saturated cohesionless soil wherein the effective shear strength is reduced to negligible value.

Earthquake. Is an oscillatory, sometimes violent movement of the ground’s surface that follows release of energy in the Earth’s Crust.

Shear Drift. The sideways deflection of a building due to lateral (sideways) loads.

Chord Drift. The sideways deflection of axial (vertical) loads.

Resultant-     Is the force which determines whether the body will be in Equilibrium or will have a varying state of motion

Hooke’s Law-  The principle used in equations related to the deformation of axially loaded material.

Poisson’s Ratio-  The ratio of the lateral to the longitudinal strain is constant.

Young’s Modulus- It is the constant of proportionality that defines the linear relationship between stress and strain.

Column-  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-  Retarding force acting opposite of body in motion.

Proportional Limit-  It is the term for the value beyond which the stress is no longer proportional to the strain.

Homogeneous-  Materials which have the same composition/compression at anypoint. or  Material has the same elastic properties in all directions.

Ductility -  Property of a material enables it to under large permanent strains before failure. or  Ability of a material to deform/ defuse in the plastic range without breaking. (2013 & 2016).

Pre-Tensioning-  It is described herein stressing high strength steel wires before concrete hardens.

Post-Tensioning -  It is described herein stressing high strength steel after the concrete has been cast and has attained sufficient strength.

Relaxation-  Is described herein loss of stress that takes place with the passage of time as concrete is held at a constant strain.

Resilience / Modulus of Resilience-  Ability of a material to absorb energy in the Elastic Range. (2016)

Toughness / Modulus of Toughness-  Ability of a material to absorb energy in the plastic range or fracture point. (2016)

Elasticity-  Property of a material which makes it return to its original dimension when the load is removed.

Center of Rigidity-  It is the point through which the resultant of the resistance to the applied lateral force acts. (2018)

Eccentricity-  It is the distance between the Center of Rigidity and Center of Mass.

Soft Story-  One in which the lateral stiffness is less than 70 percent of the stiffness of the story above is called.

Story Drift-  A Lateral Displacement of one level relative to the level above or below is called . (2021)

Center of Mass-  It is the point through which the applied seismic force acts.

Reciprocal of Stiffness-  Refers to flexibility of structure.

Orthotropic-  The material has the same composition at every point but the elastic may not be the same in all directions.

Focal Depth-  Besides the Epicenter, it describes the location of the Earthquake.

Actual Displacement or Seismic/Earthquake Waves-  It is measured by a seismometer.

Magnitude of Earthquake-  It is measured by the Richter Scale

Fatigue-  The material is subjected to repeated cycles of stress or strain, it causes the structure to breakdown ultimately leading to fracture.

Creep-  When a material has to support a load for a long period of time, what causes it to continue to deform until a sudden fracture occurs.

Plasticity-  Condition of a material when it breaks down and deforms permanently even due to a slight increase in stress above the elastic limit.

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

Torsion/Torsional Shear Stress-  It occurs when the structure’s center of mass does not coincide with its center of rigidity.

Additional Terms Proportional limit-      The greatest stress a material is capable of developing without deviation from straight line proportionality between strain and stress *

Elastic limit-      The greatest stress a material is capable of developing without a permanent elongation remaining upon complete unloading of the specimen

Modulus of elasticity-      Slope of the straight line portion of the curve or the ratio of stress over the strain

Ductility-      The ability of a material to deform in the plastic range without breakage or the ability to undergo considerable plastic deformation under tensile load before actual rupture. *

Plasticity-      A property of a material where if the specimen be unloaded, it will not return to its original length, rather it will retain a permanent elongation sometimes called a permanent set. *

Yield stress-      The stress at which there occurs a marked increase in strain without an increase in stress

Ultimate stress-      The max. stress a material is capable of developing

Rupture strength-      The stress at which the specimen actually breaks.

Stiffness-      The property of a material to withstand high stress without great strain

Brittleness-      Implies the absence of any plastic deformation prior to failure.

Malleability-      The property of a material enabling it to undergo considerable            plastic deformation under compressive load before actual rupture.

Toughness-      The property of a material enabling it to endure high- impact loads or shock loads.

Resilience-      The  property  of  a  material enabling high impact loads without inducing a stress in excess of the elastic limit.

Factor of safety-      Ratio of the failure stress to the allowable stress.

Failure-      The condition that renders the load resisting member unfit for resisting further increase in loads.

Diagonal tension-      The tensile stress that develops on the diagonals surface.

PoiSson's ratio-      The ratio of lateral strain to axial strain for an unrestrained member.

Dilatation-      Change of volume per unit volume.

Ductile material "e"-      Is one having a relatively large tensile strain up to the point of rupture

Brittle material-      Is one having a relatively small tensile strain up to the point of rupture

Tangent modulus-      The rate of change of stress with respect to strain

Specific strength-      The ratio of the ultimate or tensile strength to specific weight that is the weight per unit volume.

Specific modulus-      Ratio of the Youngs modulus to the specific weight.

 Isotropic material-      One having the same elastic properties in all directions at any one point of the body.

 Seismograph-      Is a ground mounted – device which measures the actual displacement of the ground with respect to a stationary reference point.

 Intensity-      It is the oldest useful measure of an earthquake’s strength which is based on the damage and other observed effects on people, buildings and other features.

 Dynamic - Forces generated by a body in motion.