Stuctural dynamics is a complex and increasingly important field of civil/structural engineering. The aim of this concise book is to demonstrate to practising engineers and advanced students that the dynamic response of structural systems can be understood without advanced techniques of analysis and impenetrable detail. Nearly all systems can be reduced to equivalent single-degree systems and the quality of the resulting information is often adequate for decision making. The author has therefore concentrated on single-degree systems, although multi-degree systems are introduced in the final chapter, and has employed many worked examples drawn from practice. The book is fully illustrated and exercises are provided at the end of each chapter.