EARTHQUAKE ENGINEERING TERMS Flashcards
it is the space between two adjacent floors
story
are rigid horizontal planes used to transfer lateral forces to vertical resisting elements
diaphragms
refers to a wall designed to resist lateral forces acting in its own plane, typically wind and seismic loads
shear wall
stiffened walls that are capable of transferring lateral forces from floors and roofs to the foundation
shear wall
refers to the point where the object “suffers” no torque by the effect of the gravitational force acted upon it
center of gravity
refers to the center of resistance of a floor or diaphragm against lateral forces
center of rigidity
it is the point through which the resultant of the resistance to the applied lateral force acts
center of rigidity
refers to the point through which the resultant of the masses of a system acts
center of mass
it is the point through which the applied lateral force acts
center of mass
refers to the point point through which the resultant of the restoring forces of a system acts
center of stiffness
refers to the distance between the center of rigidity and the center of mass
eccentricity
refers to the total design lateral force at the base of a structure
design seismic base shear
refers to the lateral displacement of one level relative to the level above or below
story drift
refers to the lateral displacement of the story relative to the base
story displacement
refers to the shear stress that occurs when the structure’s center of mass does not coincide with its center of rigidity
torsional shear stress
refers to the phenomenon that occurs when a building period coincides with the earthquake period
resonance
refers to the time period of undamped free vibration of a structure
natural period
refers to the rate at which natural vibration is absorbed
damping
the effect of internal friction, imperfect elasticity of material, slipping, sliding, etc. in reducing the amplitude of vibration
damping
refers to the geographical point on the surface of earth vertically above the focus of the earthquake
epicenter
refers to the origin/source of the elastic waves inside the earth which cause shaking of ground due to earthquake
focus
refers to the capacity to undergo large inelastic deformations without significant loss of strength or stiffness
ductility
refers to the state in saturated cohesionless soil wherein the effective shear strength is reduced to negligible value
liquefaction
condition when soil tends to behave like a fluid mass
liquefaction
five (5) factors that affect earthquake loads
- magnitude
- proximity of structure from fault
- type of system/structure
- occupancy
- soil properties
refers to the measure of the strength of shaking during the earthquake
intensity
it is sometimes presented in terms of observed damage
intensity
refers to the measure of total energy released in an earthquake
magnitude
this measure is often given by the Richter scale
magnitude
refers to the instrument used to record the motion of the ground during an earthquake
seismograph
the location where an earthquake is initiated
hypocenter
the location of the hypocenter is defined by the _____, _____, and _____
latitude, longitude, and depth below the surface
the point on the surface of the earth directly over the hypocenter
epicenter
five (5) vertical structural irregularities
- stiffness irregularity (soft storey)
- weight (mass) irregularity
- vertical geometric irregularity
- in-plane discontinuity in vertical lateral force-resisting element irregularity
- discontinuity in capacity irregularity (weak storey)
vertical structural irregularity:
refers to the condition wherein the lateral stiffness is less than 70% of that in the storey above or less than 80% of the average stiffness of the three stories above
stiffness irregularity (soft storey)
vertical structural irregularity:
refers to the condition wherein the effective mass of any storey is more than 150% of the effective mass of an adjacent storey; a roof which is lighter than floor below need not be considered
weight (mass) irregularity
vertical structural irregularity:
refers to the condition wherein the horizontal dimension of the lateral force-resisting system in any storey is more than 130% of that in an adjacent storey; one storey penthouse need not to be considered
vertical geometric irregularity
vertical structural irregularity:
refers to the condition wherein an in-plane offset of the lateral load-resisting elements greater than the length of those elements
in-plane discontinuity in vertical lateral force-resisting element irregularity
vertical structural irregularity:
refers to the condition wherein the storey strength is less than 80% of that in the storey above; the storey strength is the total strength of all seismic-resisting elements shearing the storey shear for the direction under consideration
discontinuity in capacity irregularity (weak storey)
five (5) horizontal structural irregularities
- torsional irregularity
- re-entrant corner irregularity
- diaphragm discontinuity irregularity
- out-of-plane offsets irregularity
- non-parallel systems irregularity
horizontal structural irregularity:
this irregularity is being considered when diaphragms are not flexible
torsional irregularity
horizontal structural irregularity:
this irregularity exists when the maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drifts of the two ends of the structure
torsional irregularity
horizontal structural irregularity:
refers to the condition wherein parts of a structure project beyond a reentrant corner a distance greater than 15% of the plan dimensions in the given direction
re-entrant corner irregularity
horizontal structural irregularity:
refers to the condition wherein diaphragms with abrupt discontinuities or variations in stiffness, including those having cutout or open areas greater than 50% of the gross enclosed area of the diaphragm, or changes in effective diaphragm stiffness of more than 50% from one-story to the next
diaphragm discontinuity irregularity
horizontal structural irregularity:
refers to the condition wherein there are discontinuities in a lateral force path, such as out-of-plane offsets of the vertical elements
out-of-plane offsets irregularity
horizontal structural irregularity:
refers to the condition wherein the vertical lateral-load-resisting elements are not parallel to or symmetric about the major orthogonal axes of the lateral force-resisting systems
non-parallel systems irregularity
