Structural Engineering Terms

Strain energy

refers to the energy stored in a material due to its deformation.

Modulus of toughness

indicates the maximum amount of strain-energy the material can absorb just before it fractures (ability to absorb energy in plastic range).

Modulus of Resilience

represents the largest amount of internal strain energy per unit volume the material can absorb without causing any permanent damage to the material (ability to absorb energy in the elastic range)

Elasticity

refers to the property of a material which makes it return to its original state when the load is removed.

Ductility

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

Stiffness

ability to resist a deformation within the linear range. This is equal to the amount of force required to produce unit deformation. Inverse of stiffness is flexibility.

Toughness

refers to a material's resistance to fracture.

Hardness

refers to a material's resistance to indentation.

Ductile Material

is any material that can be subjected to large strains before it fractures.

Brittle Materials

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

Homogeneous material

is a material that has the same physical and mechanical properties throughout its volume or material has the same composition at any point.

Isotropic material

is a material that has same physical and mechanical properties in all directions.

Orthotropic material

is a material that has properties at a particular point, which differ along three mutually-orthogonal axes.

Prismatic

describes a member with the same cross sections throughout its length.

Creep

When a material must support a load for a very long period, it may continue to deform until a sudden fracture occurs or its usefulness is impaired. This time dependent permanent deformation is known as creep.

Fatigue

When a material is subjected to repeated cycles of stress or strain, it causes its structure to break down, ultimately leading to fracture. This behavior is called fatigue.

Buckling

lateral deflection that occurs when long slender members are subjected to an axial compressive force.

Yielding

A slight increase in stress above the elastic limit will result in a breakdown of the material and causes it to deform permanently. This behavior is called yielding 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, until it reaches a maximum stress referred to as the ultimate stress.

Necking

Just after the ultimate stress, the cross-sectional area will begin to decrease in a localized region of the specimen, until the specimen breaks at the fracture stress.

Story

It is the space between two adjacent floors

Diaphragms

are rigid horizontal planes used to transfer lateral forces to vertical resisting elements.

Shear wall

refers to a wall designed to resist lateral forces acting in its own plane, typically wind and seismic loads.

stiffened walls are capable of transferring lateral forces from floors and roofs to the foundation.

Center of gravity

refers to the point where the object "suffers" no torque by the effect of the gravitational force acted upon it.

Center of rigidity

refers to the center of resistance of a floor or diaphragm against lateral forces - It is the point through which the resultant of the resistance to the applied lateral force acts.

Center of mass

refers to the point through which the resultant of the masses of a system acts. - It is the point through which the applied lateral force acts.

Center of stiffness

refers to the point point through which the resultant of the restoring forces of a system acts.

Eccentricity

refers to the distance between the center of rigidity and the center of mass.

Design seismic base shear

refers to the total design lateral force at the base of a structure.

Story drift

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

Story displacement

refers to the lateral displacement of the story relative to the base

Out-of-plane offsets

refers to the discontinuities in a lateral force path

Torsional shear stress

refers to the shear stress that occurs when the structure's center of mass does not coincide with its center of rigidity

Resonance

refers to the phenomenon that occurs when a building period coincides with the earthquake period.

Natural period

refers to the time period of undamped free vibration of a structure.

Damping

refers to the rate at which natural vibration is absorbed. - The effect of internal friction, imperfect elasticity of material, slipping, sliding, etc in reducing the amplitude of vibration

Epicenter

refers to the geographical point on the surface of earth vertically above the focus of the earthquake.

Focus

refers to the origin/source of the elastic waves inside the earth which cause shaking of ground due to earthquake.

Ductility

refers to the capacity to undergo large inelastic deformations without significant loss of strength or stiffness.

Liquefaction

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

- condition when soil tends to behave like a fluid mass.

Intensity

refers to the measure of the strength of shaking during the earthquake

Magnitude

refers to the measure of energy released in an earthquake.

Seismograph

refers to the instrument used to record the motion of the ground during an earthquake.

Soft Storey Irregularity

refers to the condition in which the lateral stiffness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stiffness of the three storeys above.

Weak Storey Irregularity

refers to the condition is one in which the storey lateral strength is less than 80 percent of that in the storey above.