Page 10 - Dynamic Loading and Design of Structures

Page xi

Preface

The dynamical behaviour of civil engineering structures has traditionally been tackled, for
design purposes, in an ‘equivalent static’ way, essentially by introducing magnification
factors for vertically applied loads and/or by specifying equivalent horizontal loads. Today the
availability of software able to deal explicitly with dynamic analysis of realistic structures
with many (dynamic) degrees of freedom, as well as the outcome of the valuable research
carried out in the various fields included under ‘Dynamics’, make this type of analysis a part
of everyday life in the design office.
There are also a number of good reasons why dynamical behaviour of buildings, bridges
and other structures is now more of a concern for the designer than it used to be 20 or 30
years ago. One reason is that the aforementioned structures currently consist of structural
members that are more slender than before, and lighter cladding made of metal and glass or
composites rather than of brick walls. This offers a number of architectural advantages, but
also makes these structures more sensitive to vibration, due to their reduced stiffness. From
another perspective, the risk to environmental dynamic loads, like those from earthquakes, has
increased due to the tremendous increase in urbanization witnessed in many countries subject
to such hazards. Furthermore, the increased need for building robust and efficient structures
inside the sea has also placed more emphasis on properly designing such structures against
dynamic loading resulting from waves and currents.
Dealing with all, or even some of the aforementioned dynamic loads in an explicit way is
clearly a challenge for the practising engineer, since academic curricula can hardly
accommodate a proper treatment of all these loads. Furthermore, the lack of a book dealing
with all types of dynamic loading falling within the scope of current codes of practice, makes
the problem even more acute.
The main purpose of this book is to present in a single volume material on dynamic loading
and design of structures that is currently spread among several publications (books, journals,
conference proceedings). The book provides the background for each type of loading (making
also reference to recent research results), and then focuses on the way each loading is taken
into account in the design process.