DYNAMICS OF VIBRATION Flashcards
defined as the oscillating, reciprocating, or other periodic motion of a
rigid or elastic body or
medium forced from a
position or state of
equilibrium
Vibration
Types of Vibration
Free Vibration:
Forced Vibration
Occurs
when a system
oscillates due to an
initial disturbance
without external forces.
Free Vibration:
Occurs when an
external force
continuously drives the
system
Forced Vibration:
Types of Free Vibration
Undamped Free Vibration:
Damped Free Vibration
occurs when energy is
gradually lost due to forces like air resistance or friction, leading to a decrease in the
amplitude over time
Damped Free Vibration
no energy is lost from the
system during oscillation,
meaning the system
continues to vibrate
indefinitely with the same
amplitude
Undamped Free Vibration
Types of Forced Vibration
Undamped Forced
Vibration
Damped Forced
Vibration
the system is driven by an externalforce, but energy is dissipated due to
damping
Damped Forced
Vibration
Undamped Forced
Vibration
the system vibrates due to thecontinuous application of an external force, and no energy is lost
is the simplest representation of a dynamic system, where the motion or displacement of the system can be described by a single variable (degree of freedom)
Single Degree of Freedom (SDOF) Systems
The ______________
assumes that the structure or mechanical system behaves as
a single mass, moving in one direction (either horizontally or
vertically) in response to external forces
SDOF system
is a more complex and realistic model that represents structures or mechanical systems that can move in multiple
independent directions or exhibit more complex motion.
MDOF (Multiple Degrees of Freedom)
System
the process by which a
structure dissipates the energy imparted to it by external forces such
as seismic events or wind.
Damping
The primary
purpose of ___________is to reduce the amplitude of vibrations caused by these
dynamic forces
damping
The NSCP assumes a typical damping ratio of _____% of critical
damping for buildings.
5
used in structural engineering to
evaluate how a building or structure will respond to seismic activity.
RESPONSE SPECTRUM ANALYSIS
It involves creating a response spectrum—a graphical representation that shows a structure’s maximum expected
response (such as displacement, velocity, or acceleration) at
various natural frequencies when subjected to earthquake forces
RESPONSE SPECTRUM ANALYSIS
It is the time needed to finish one
cycle of vibration.
NATURAL TIME PERIOD (T)
FACTORS AFFECTING WAVE PROPAGATION
Soil type
Distance from the Epicenter
Geological Conditions
the speed or rhythm at which something tends to vibrate naturally when it’s shaken or disturbed
Natural frequency
occurs when the frequency of an external
force (such as seismic waves during an earthquake)
matches the natural frequency of a structure.
resonance
Can be defined as Separating or Decoupling the structure from its
Foundation
Base Isolation Technique
It is developed to prevent or minimize damage to building during an
earthquake.
Base Isolation Technique
One of the most widely implemented seismic protection system
Base Isolation Technique
devices THAT can enhance the performance, safety, and comfort of
structures by dissipating the kinetic energy of the vibrations and
transferring it to other forms of energy, such as heat or sound
Damping devices
Common Types of Damping Devices
Tuned Mass Dampers
Viscous Fluid Dampers
Tuned Liquid Dampers
A mass, typically suspended inside
a structure, that moves in
opposition to building motion, reducing oscillation
Tuned Mass Dampers
Uses hydraulic fluid to absorb energy through resistance to motion.
THese are often installed in highrise buildings or bridges to reduce vibration and sway caused by earthquakes or wind
Viscous Fluid Dampers
Uses the sloshing of liquid (often water) in large tanks to counteract building vibrations.
The liquid moves in response to seismic or wind-induced vibrations
and creates a counteracting force
that reduces motion.
Tuned Liquid Dampers
process of strengthening existing structures to make them more
resistant to seismic forces.
Seismic Retrofitting
Measure the acceleration of the ground or a structure during an
earthquake
Accelerometers
Measure the relative
movement between different
structural elements or between a
structure and the ground.
Displacement Sensors
Measure the tilt or inclination
of structures to detect changes in
orientation due to seismic activity.
Tiltmeters
Measure deformation or strain in structural components caused by
applied forces
Strain Gauges
Placed at critical points within the structure, such as connections
or load-bearing members, to
measure forces acting on them during seismic events.
Load Cells
collect and analyze
data from different sensors (e.g.,
accelerometers, strain gauges, and
displacement sensors) to give a comprehensive view of a structure’s
condition
Structural Health Monitoring (SHM)
Systems
These systems provide real-time
feedback on the effectiveness of
seismic retrofitting and help detect
potential failures before they occur.
Structural Health Monitoring (SHM)
Systems
