Chapter 1
Introduction
1.1 Introduction
Majority of today’s structures is subjected to load which varies with time. In fact,
with the possible exception of dead load, no structural load can really be considered
as static. However, in many cases the variation of the force is slow enough, which
allows the structures to be treated as static. For highrise buildings subjected to wind
and earthquake, offshore platforms surrounded by waves, aeroplanes flying through
storms, vehicles moving on the road, reciprocating engines, rotors placed on the floor
and many other categories of loading, the dynamic effect associated with the load
must be accounted for in the proper evaluation of safety, performance and reliability
of these systems.
Many of the structures such as buildings, slab-beam bridges, ship, etc. are designed
on the basis of static or pseudo-static analysis. The main reason for so doing lies in the
simplicity of these analyses. A dynamic analysis of structures is much more involved
and time consuming than an equivalent static analysis. Structures thus designed have
been found to be safe, though no idea could be obtained from this as to the extent of
its safety as also to its actual behaviour.
The analysis of vibration problems in machines follows a similar approach. The
torsional vibrations of shafting systems with its gearing arrangement, the vibration
of turbine blades, the whirling of rotating shafts and various other related problems
have assumed added significance. The effective working condition of these mechanical systems, keeping them free from critical conditions associated with vibration,
can only be achieved from a thorough understanding of the vibration analytical
procedures.
With high-speed digital computers at the disposal of the analyst, and the tremendous advancement made in the analytical and numerical procedures, more accurate
representation of the structural behaviour due to dynamic loads, as also the study of
more complex problems related to machine vibrations have now become possible.
As such, many of the structures which could not have been conceived in terms
of its length and breadth even four decades ago have become a reality today. Large
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Mukhopadhyay, Structural Dynamics,
https://doi.org/10.1007/978-3-030-69674-0_1
1
Introduction
1.1 Introduction
Majority of today’s structures is subjected to load which varies with time. In fact,
with the possible exception of dead load, no structural load can really be considered
as static. However, in many cases the variation of the force is slow enough, which
allows the structures to be treated as static. For highrise buildings subjected to wind
and earthquake, offshore platforms surrounded by waves, aeroplanes flying through
storms, vehicles moving on the road, reciprocating engines, rotors placed on the floor
and many other categories of loading, the dynamic effect associated with the load
must be accounted for in the proper evaluation of safety, performance and reliability
of these systems.
Many of the structures such as buildings, slab-beam bridges, ship, etc. are designed
on the basis of static or pseudo-static analysis. The main reason for so doing lies in the
simplicity of these analyses. A dynamic analysis of structures is much more involved
and time consuming than an equivalent static analysis. Structures thus designed have
been found to be safe, though no idea could be obtained from this as to the extent of
its safety as also to its actual behaviour.
The analysis of vibration problems in machines follows a similar approach. The
torsional vibrations of shafting systems with its gearing arrangement, the vibration
of turbine blades, the whirling of rotating shafts and various other related problems
have assumed added significance. The effective working condition of these mechanical systems, keeping them free from critical conditions associated with vibration,
can only be achieved from a thorough understanding of the vibration analytical
procedures.
With high-speed digital computers at the disposal of the analyst, and the tremendous advancement made in the analytical and numerical procedures, more accurate
representation of the structural behaviour due to dynamic loads, as also the study of
more complex problems related to machine vibrations have now become possible.
As such, many of the structures which could not have been conceived in terms
of its length and breadth even four decades ago have become a reality today. Large
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Mukhopadhyay, Structural Dynamics,
https://doi.org/10.1007/978-3-030-69674-0_1
1