Download CVE 503 ASSIGNMENT PREPARED BY SALAWU AKINYINKA 12

CVE 503 ASSIGNMENT PREPARED BY SALAWU AKINYINKA 12/ENG04/057
1. DEFINE STRUCTURAL DYNAMICS
Structural dynamics is the response of physical objects to time varying loading, it is an important area of
study in engineering. The physical object whose response is sought may either be treated as rigid body or
deformable body. The rigid body dynamics treats the object as rigid that will undergo motion without
deformation when subjected to dynamic loading for example, movement of machinery, flight of an
aircraft or space vehicle etc. In many instances however, dynamic response involving deformation rather
than simple rigid motion is of primary concern. This is particularly so in the design of structural frames,
for example, buildings, bridges, aircrafts, ships, offshore platforms etc.
All of these structures and their support systems are subjected to dynamic disturbances during their
service life.
2. STATE THE APPLICATION/IMPORTANCE OF STRUCTURAL DYNAMICS TO
ENGINEERING DESIGNS.
The basis of vibration analysis is predicting the structural response when the external load acting on it is
varying with respect to time.
The analysis of structural response is of considerable importance in the design of structures as:
1. Under certain situations, vibrations may cause large deformation and severe stress in the structure. This
may happen particularly when the frequency of existing force coincides with the natural frequency of the
structure.
2. Fluctuating stresses, even of moderate intensity, may cause material failure through fatigue if the
number of repetitions is large enough.
3. Oscillating motion may at times cause wearing and malfunctioning.
4. Vibration induced by rotating or reciprocating machinery, for example, transmitted through the support
structure to delicate instruments elsewhere on it causing such instruments to malfunction.
5. When structure is designed for human use, vibratory motion may result in severe discomfort to the
occupants.
CVE 503 ASSIGNMENT PREPARED BY SALAWU AKINYINKA 12/ENG04/057
3. DIFFERENTIATE WITH EXAMPLES, FORCED AND FREE VIBRATIONS
Free vibration is the response of a system that is not subjected to external force but is excited by some
initial disturbances is called free vibration i.e. vibrations are excited by initial disturbances
Free vibration occurs when a system is set in motion with an initial input and allowed to vibrate freely.
Examples of this type of vibration are:
1. Pulling a child back on a swing and letting go
2. Hitting a tuning fork and letting it ring.
While Forced vibration is the to and fro movement of the structure due to external excitation i.e.
vibrations are caused due to external excitation.
It is when a time-varying disturbance (load, displacement or velocity) is applied to a system. The
disturbance can be a periodic and steady-state input, a transient input, or a random input. The periodic
input can be a harmonic or a non-harmonic disturbance.
Examples of these types of vibration include:
1. A washing machine shaking due to an imbalance
2. Transportation vibration caused by an engine or uneven road
3. The vibration of a building during an earthquake
For linear systems, the frequency of the steady-state vibration response resulting from the application
of a periodic, harmonic input is equal to the frequency of the applied force or motion, with the response
magnitude being dependent on the actual mechanical system.