Earthquake-Resistant Design of Masonry Buildings This page is intentionally left blank Series on Innovation in Structures and Construction — Vol. 1 Earthquake-Resistant Design of Masonry Buildings Miha Tomazevic Slovenian National Building and Civil Engineering Institute Imperial College Press ICP \ Published by Imperial College Press 57 Shelton Street Covent Garden London WC2H 9HE Distributed by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Tomazevic, Miha. Earthquake-resistant design of masonry buildings / Miha Tomazevic. p. cm. — (Series in innovation in structures and construction; vol. 1) Includes bibliographical references and index. ISBN 1-86094-066-8 1. Masonry. 2. Buildings. 3. Earthquake resistant design. I. Title. II. Series. TH5321.T66 1999 693.8'52-dc21 99-18293 CIP British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. First published 1999 Reprinted 2000, 2006 Copyright © 1999 by Imperial College Press All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. Printed by Fulsland Offset Printing (S) Pte Ltd, Singapore PREFACE From many points of view, writing this book Earthquake-Resistant Design of Masonry Buildings was not an easy task. In most countries, masonry is still used as a traditional, n on-engineered construction material: in this regard, the engineering approach to masonry construction had to be encouraged. Several, although not many, books on this topic have been published in the last decade, therefore, a touch of originality had to be given to this book. And most importantly, taking into account the complexity of masonry construction world­ wide, the request that the book should be useful for a broad readership of structural engineers, interested in earthquake resistant design of masonry buildings, has to be respected. In the recent books on masonry structures, the idea that reinforced grouted masonry is the earthquake-resistant type of masonry construction, is usually followed. However, buildings built by traditional masonry construction systems, such as plain and confined, as well as reinforced masonry, where normal or specially shaped hollow or perforated masonry units are used to accommodate the reinforcement, embedded in mortar or concrete, can also resist earthquakes. As in most countries these buildings outnumber reinforced grouted masonry ones. The discussion in this book is limited to traditional, unreinforced and reinforced masonry construction systems. However, general aspects of earthquake-resistant masonry construction are preferred to details specific for different masonry construction systems. In order to assist the implementation of the recent European structural design codes, Eurocodes, where a clear concept for limit states verification has also been introduced for masonry structures, the concepts of Eurocodes' structural verification philosophy, which has general validity, are followed. However, although detailed information is given on the requirements of Eurocodes, it was not the aim of the book to collect a set of design and construction rules, accompanied^^w^h^j&leyant equations for structural V VI Earthquake-Resistant Design of Masonry Buildings verification, and produce a state-of-the-art manual for structural engineers who wish to become familiar with earthquake-resistant design of masonry buildings. There have been excellent books on masonry published recently which more than fulfil this task. Being involved in experimental research in seismic behaviour of masonry structures for most of my career, now 30 years long, I have ambitiously decided to make the readers familiar with masonry "behind the scenes". Namely, an attempt has been made in this book to provide information regarding the actual behaviour of masonry structures when subjected to earthquakes, as well as to present experimental background for the development of mathematical models for seismic resistance verification. It is hoped that the readers will better understand the design philosophy and the meaning of parameters in the design equations. Therefore, experimental evidence to support the criteria and mathematical models is provided, wherever possible. Given the opportunity, the methods developed on the basis of experimental research, carried out in Ljubljana, are mainly presented and discussed. Although the book is not a review of state-of-the-art earthquake-resistant design of masonry structures, an attempt has been made to balance the discussion on recent code requirements, the state-of-the-art methods of earthquake-resistant design, and my research work in order to make the book useful for a broader application in the design practice. I have also attempted to present, in a condensed but easy to understand way, all the information needed for earthquake-resistant design of masonry buildings constructed in traditional masonry construction systems. The book first deals with earthquakes and seismic performance of masonry buildings. To be compatible with Eurocodes, the new European macroseismic scale is briefly presented as a measure of earthquake intensity. Then, the basic aspects regarding the selection of masonry materials and construction systems are discussed, including the testing methods for the determination of mechanical properties of masonry materials and evaluation of test results. Next, the architectural and structural aspects of earthquake-resistant masonry construction are discussed. The requirements regarding the shape and dimensions of buildings are given. Simple buildings, in which the verification of seismic resistance by calculation is not mandatory, are described. In the chapters to follow, the basic concepts of limit states verification are presented and equations for seismic resistance verification of masonry walls of all types of masonry construction — unreinforced, confined, and reinforced — Preface Vll as well as masonry infilled reinforced concrete frames, are explained. A method for seismic resistance verification, compatible with recent code requirements, is discussed. In all cases, experimental results are used to explain the proposed methods and equations. Finally, an important part of the book discusses the problems of seismic repair, retrofit and rehabilitation of existing masonry buildings, including historical houses in urban nuclei. Methods of strengthening the masonry walls, as well as improving the structural integrity of existing buildings, are described in detail. Wherever possible, experimental evidence regarding the effectiveness of the proposed strengthening methods is given. A list of references is given at the end of each chapter. Considering the concept of writing the book, the list of references has no intention of providing information regarding the state of the art of the topic discussed. It is only aimed at orienting the reader to the source where he/she could obtain additional background information. Although an attempt has been made to cover as many problems related with the earthquake-resistant design of masonry buildings as possible, not everything could have been mentioned in the book. At least two important issues in the field of modern masonry construction have been completely omitted. Consequently, the interested reader should search, on his own, for information regarding the large panel prefabricated construction, which is used in the case of residential masonry buildings, and seismic isolation, which can be applied to new and existing masonry buildings. It is my pleasure to acknowledge Imperial College Press, who have given me opportunity to write this book. My gratitude also goes to former and recent colleagues who have assisted me in carrying out my research in the past years: most of their names can be found on the list of references in individual chapters. Without them, there would not be much to write about in this book. Although most of the technical work is now done by powerful computers, the hands of Ms Zvonka Rekece were needed to prepare the drawings. Last but not least, my deepest thanks go to Natasa and Nejc — who have not seen much of their husband and father recently — for their encouragement and support during the days when the end of this adventure had seemed unattainable. Miha TomaZevic This page is intentionally left blank CONTENTS PREFACE v 1. INTRODUCTION 1 2. EARTHQUAKES AND SEISMIC PERFORMANCE OF MASONRY BUILDINGS 5 2.1 Introduction 5 2.2 Earthquakes and Seismic Ground Motion 6 2.2.1 Causes of earthquakes 6 2.2.2 Seismic waves and earthquake ground motion 9 2.2.3 Magnitude and intensity 11 2.2.4 Occurrence of earthquakes 17 2.2.5 Earthquake ground motion and effects on buildings 18 2.3 Seismic Performance of Masonry Buildings 25 2.3.1 Structural typology 25 2.3.2 Seismic performance and classification of damage 28 2.4 References 32 3. MASONRY MATERIALS AND CONSTRUCTION SYSTEMS 35 3.1 Introduction 35 3.2 Masonry Materials 36 3.2.1 Masonry units 36 3.2.2 Mortar 41 3.2.3 Concrete infill 42 3.2.4 Reinforcing steel 43 3.2.5 Masonry 45 ix