Preface

As a natural material, timber is unique, innovative and easy to handle. It is sustainable, environmentally friendly, can be readily recycled, and as sawn sections or quality-controlled engineered products, timber has a large potential market for use as a structural and building material. However, the existing civil and structural engineering curricula neglect, to a large extent, the importance of timber as a viable engineering material and as a consequence relatively few textbooks provide information on the design of timber structures. Also, most books have tended to concentrate on designs in accordance with BS 5268, a permissible stress-based design, with limited information on designs to Eurocode 5, which is based on a limit states design philosophy.

BS 5268 is to be replaced by Eurocode 5 in the very near future and all timber designs in the United Kingdom will have to be carried out in accordance with this code. This book is based solely on the use of Eurocode 5: Design of Structures. Part 1-1: General -Common Rules and Rules for Building, referred to as EC5 in the book, and incorporates the requirements of the associated UK National Annex. There is a pressing need for practising engineers as well as specialist contractors, postgraduate and undergraduate students of civil and structural engineering courses to become familiar with the design rules in EC5 and this book offers a detailed explanation and guide to the use of the code. It provides comprehensive information and a step-by-step approach to the design of elements, connections and structures using numerous worked examples and encourages the use of computers to carry out design calculations.

Chapter 1 introduces the nature and inherent characteristics of timber and gives an overview of timber and its engineered products as structural and building materials, and includes design-related information on the strength and stiffness properties required for design in accordance with the requirements of EC5. In Chapter 2 the design philosophy used in Eurocodes is explained. It includes information on the relevance of the requirements of Eurocode 0 to EC5 as well as the significance of the effects of moisture content, load duration, creep behaviour and size factors etc., in the design process.

Chapter 3 gives an overview of Mathcad®, a computer software package used to carry out mathematical calculations, and details its simplicity and the advantages that it provides when used for design calculations. The software is commonly used in design offices and universities and the aim is to encourage readers to use computing as a tool to increase their understanding of how design solutions vary in response to a change in one or more of the variables and how alternative design options can be easily investigated. The design of basic elements is explained and illustrated in Chapters 4 and 5 whilst the design of more specialised elements such as glued-laminated straight, tapered and curved beams and columns, thin webbed and thin flanged beams and built-up columns is covered in Chapters 6-8 using numerous worked examples.

In Chapter 9, the lateral stability requirements of timber structures are addressed, and the design of stability bracing and the racking resistance of floor and wall diaphragms using the rules in EC5 are explained.

The design of connections using metal dowel type fasteners is covered in Chapter 10. It includes an overview of the theory used for connection design together with a comprehensive coverage of the lateral and axial strength requirements of nailed, screwed and bolted joints. The lateral stiffness behaviour of these types of connections is also covered in Chapter 10 as well as the design of connections with multiple shear planes. Several step-by-step worked examples are provided to illustrate the design methods explained in this chapter.

Chapter 11 covers the strength and stiffness behaviour of connectors such as toothed plates, split-rings and shear plates. In Chapter 12, the design of rigid and semi-rigid connections subjected to combined moment and lateral forces is addressed with examples showing the significant effect on joint and member behaviour when semi-rigid behaviour is included in the design process.

At the time of publication of the book a Draft Amendment A1 to EC5 is being processed. An outline of the proposed changes being considered is given in Appendix C and where an amendment will result in a change to the design procedure described in the book, reference is made to the draft proposal in the text.

All design examples given in this book are produced in the form of worksheet files and are available on a CD to run under Mathcad Version 11, or higher. Details are given at the back of the book (see page 542). The examples are fully self-explanatory and well annotated and the authors are confident that the readers, whether practising design engineers, course instructors or students, will find them extremely useful to produce design solutions or prepare course handouts. In particular, the worksheets will allow design engineers to undertake sensitivity analyses to arrive at the most suitable/economic solution(s) very quickly.

To prevent any confusion between the numbering system used in the book and that used in the Eurocodes, where reference is made in the text to a specific section, item number, or table in a Eurocode and/or its accompanying UKNA, it is given in italics. For example 6.4.2 refers to item 6.4.2 of EC5 whereas 6.4.2 refers to Section 6.4.2 in Chapter 6 of the book.

Permission to reproduce extracts from British Standards is granted by BSI. British Standards can be obtained from BSI Customer Services, 389 Chiswick High Road, London W4 4AL. Tel: +44 (0)20 8996 9001. email: [email protected]

Chapter 1

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