**Preface**

This is the second edition of *Seeing and Touching Structural Concepts* with a revised title, *Understanding and Using Structural Concepts*. The previous title highlighted ways to aid understanding of structural concepts, whilst the current one emphasises both understanding and application of structural concepts. The objective of understanding structural concepts is to enable their use in a creative way to solve practical engineering problems, leading to safe, economical and elegant designs.

This change of the title reflects the nature and our understanding of structural concepts. Structural concepts are defined in this new edition as follows:

A structural concept is *a qualitative and concise representation of a mathematical relationship between physical quantities, which captures the essence of the relationship and provides a basis for practical applications in structural engineering*.

This definition shows that structural concepts present a sound understanding of theory, bring together mathematics, physical understanding and engineering practice as a whole and indicates a suitable way to learn and to study.

Structural concepts can be learned from theory in textbooks, in an abstract way, but they can also be learned, in an intuitive way, through the use of physical models and practical examples. The latter method appears more enlightening, inspiring and interesting, but greater numbers of physical models and appropriate practical examples need to be made available in textbooks. It would be ideal if the two ways of learning could be integrated to complement each other. This book aims to develop such an intuitive way of learning structural concepts in conjunction with conventional learning from theory. This is achieved through:

- providing a series of simple demonstration models for illustrating structural concepts, or the effect of the concepts, which provides an easy and quick way to comprehend theory;
- providing associated examples in engineering practice and in everyday life to demonstrate the innovative application of structural concepts, which illustrates the use of structural concepts and helps to bridge the gap between knowledge and practice;
- converting appropriate research output, which particularly involves structural concepts, into teaching material to improve and update existing course contents.

Physical models are real, simple and can be created to illustrate particular structural concepts. The models in this book are often presented in pairs, one with, and one without, the involvement of a structural concept. Thus the different behaviour of the two can be seen and felt. The models can be demonstrated by lecturers in class or used by students after class. Many photos are used to illustrate these models and their actions.

Practical examples, in which structural concepts are used innovatively, will show how structural concepts are actually used to produce effective engineering solutions. These examples take students from structural elements to whole structures, and from understanding to application. They also provide an opportunity to appreciate the creativity of engineers and architects in producing solutions to practical problems.

The study of structural concepts brings together practice, research and teaching; each contributing to, and benefiting from, the other two. Research based on emerging engineering problems has lead to the identification of new concepts and to the provision of new examples, which effectively enrich the teaching and learning of structural concepts. Some of the contents in several chapters in this book are developed from such research.

In addition to achieving a better understanding, real interest in learning can be generated by seeing many physical models and practical examples. It has been observed in class situations that students show a greater interest in topics which are demonstrated physically than in topics that are explained by words and blackboard/OHP/PowerPoint presentations alone. They show an even greater interest in practical examples which illustrate the use of concepts in the solution of engineering problems than in coursework examples. Students are motivated by "hands on" experience and by linking concepts and models to real engineering problems.

The new edition makes the following changes and improvements:

- An Introduction chapter is provided to give an overview of structural concepts and a guide on how to learn and to use this book.
- A new part, Synthesis, is added to the existing Statics and Dynamics parts. It contains four new chapters discussing the relationships between static and modal stiffnesses, between static and dynamic problems, between experimental and theoretical studies and between theory and practice.
- A small number of problems are provided at the end of each chapter in the Statics and Dynamics parts.
- Some new models and examples are added.

The Statics part contains 12 chapters and the Dynamics part 7 chapters. The new part, Synthesis, aims to integrate statics and dynamics. Static stiffness and modal stiffness are widely used in engineering practice and they are normally dealt independently. Chapter 21 studies such a relationship, provides a theoretical basis for the relationship and explores its applications. The relationships between some static and dynamic problems are examined in Chapter 22 allowing some statics methods to be used to solve problems in dynamics, and some dynamics methods to solve problems in statics, to produce effective solutions of practical problems. The last two chapters present evidence based studies. Chapter 23 develops relationship models between experimental and theoretical studies, which appear to be research oriented. This is stimulated by the modelling used in Economics and illustrated using many real cases. The relationships between theory and practice are explored in Chapter 24, through reviewing the role of structural concepts. The content in this chapter may not be mature or complete, but the exploration is supported through the use of many examples.

The contents of this book are an outcome of our many years of teaching, research and engineering practice in which structural concepts are concerned. This book provides numerous demonstrations using physical models and practical examples. A significant amount of material, not found in current textbooks, is included, to enhance the understanding of structural concepts and stimulate interest in learning, creative thinking and design. This book will be of interest to all engineers, from students to consultants. It will be useful to civil and structural engineering students, including postgraduates, in all years of their courses as well as the more technically-minded architecture students and practising engineers.

Accompanying this book, we have created a website, Seeing and Touching Structural Concepts, which can be found at www.structuralconcepts.org. The website contains most of the contents presented in the first, third and fourth sections of each chapter in the Statics and Dynamics parts of the book, and selected student submissions for their coursework on Understanding and Using Structural Concepts.

Tianjian Ji, Adrian Bell

School of Mechanical, Aerospace and Civil Engineering

The University of Manchester, UK

Brian R Ellis

Brian Ellis Consultants,

St Albans, UK