Structural Design

Guide to the

Building Code

~.

Structural Design Guide to the

Building: Code

Edward S. Hoffman President

Edward S. Hoffman, Ltd., Chicago, IL

David P. Gustafson Vice President of Engineering

Concrete Reinforcing Steel Institute, Schaumburg, IL

Albert j. Gouwens President

Gouwens Engineering Consultants, Inc., Elmhurst, IL

" SPRINGER SCIENCE+BUSINESS MEDIA, LLC

Library of Congress Cataloging-in-Publication Data

A C.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-1-4419-4725-3 ISBN 978-1-4757-6619-6 (eBook) DOI 10.1007/978-1-4757-6619-6

Copyright © 1998 by Springer Science+Business Media New York Originally published by Kluwer Academic Publishers in 1998

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, mechanical, photo­copying, recording, or otherwise, without the prior written permission of the publisher, Springer Science+Business Media, LLC.

Printed on acid-free paper.

Preface

This book is intended to guide practicing structural engineers familiar with ear­lier ACI building codes into more profitable routine designs with the ACI 1995 Building Code (ACI 318-95).

Each new ACI Building Code expresses the latest knowledge of reinforced concrete in legal language for safe design application. Beginning in 1956 with the introduction of ultimate strength design, each new code offered better uti­lization of high-strength reinforcement and the compressive strength of the con­crete itself. Each new code thus permitted more economy as to construction material, but achieved it through more detailed and complicated design calcula­tions. In addition to competition requiring independent structural engineers to follow the latest code for economy, it created a professional obligation to fol­low the latest code for accepted levels of structural safety.

The increasing complexity of codes has encouraged the use of computers for design and has stimulated the development of computer-based handbooks. Before computer software can be successfully used in the structural design of buildings, preliminary sizes of structural elements must be established from handbook tables, estimates, or experienced first guesses for input into the com­puter.

This book will guide the user to the various sections of the Code pertinent to design of common reinforced concrete structural elements. A brief explanation of the significance of these sections is presented, together with limits of applic­ability, the range in which results may control design; and, where possible, design short cuts to ensure automatic conformance to the Code without calcula­tions.

This Guide does not duplicate nor replace the ACI Code, its Commentary, design handbooks, or use of computers. It complements the ACI Code and Com­mentary, shows how to take full advantage of available handbooks based on the Code, and should shorten time to develop computer design programs. It converts some code formulas from the review form (or trial designs) to direct design. It presents some simple appropriate formulas, tabulations, and charts for conserv­ative longhand direct design.

Specifications for materials and special Code requirements superimposed upon the ASTM Specifications for materials are explained to aid the structural engineer to avoid difficulties with use of obsolete specifications.

vi / Structural Design Guide to the ACI Building Code

The overall objective of this book is simply to save the engineer time in rein­forced concrete design.

HOW TO USE THIS GUIDE

Code requirements applicable to the design of structural building elements, scat­tered through various Code chapters, have been assembled for the analysis and design of one-way slabs, one-way joists, beams, the various types of two-way slab systems with and without beams, prestressed flexural members, columns, walls, and footings.

Most of the numerical examples are based on normal weight concrete with f: = 4,000 psi for flexural members and 4,000, 5,000, or 6,000 psi for columns; and the standard Grade 60 reinforcement. For lightweight aggregate concrete, see Chapter 15. Other concrete strengths used are so indicated.

Provisions new to the Code are noted as such for especial attention. It is assumed that users of the guide are familiar with reinforced concrete design and structural analysis as well as the terms and symbols in common use.

This Guide is intended for use with the Code itself. Space limitations make it impracticable to include the Code. The Guide indicates the proper sections of the Code in the order that a designer would normally require their use for design of a particular building element. In the appropriate chapter for the element being designed, the engineer will find the applicable Code sections indicated in paren­thesis thus: "(Section 00.00.00)" following the explanations of their application.

Explanations of requirements difficult to interpret are followed by numerical examples. Where several Code equations or requirements are applicable simul­taneously and must be solved to determine which controls, computer solutions over the usual range have been included as convenient tables or curves. Where examination of computer solutions over a wide range show simple approxima­tions by longhand possible, such short cuts, together with the limitations of range or accuracy are given. For especially difficult or unusual problems out­side the scope of this guide, other references are cited to guide the engineer to a quick source of information for detailed study. References to the ACI Code Commentary are indicated thus: "(Commentary ROO.OO.OO)."

No attempt has been made to explain each individual Section of the Code in this book. A large number of Code provisions which have provoked little or no question of interpretation in past codes have been repeated essentially without change in the 1995 Code.

Other exclusions are precast concrete and composite (precast with cast­in-place concrete) design procedures which involve no separate design theory but merely consideration of different load conditions due to construction sequences. An alternate (working stress) design method is permitted by Appen­dix A of the Code, but the working stress design method is uneconomical. The Code provisions for thin shell and folded-plate design serve only to include

Preface / vii

these structures within the scope of the Code. The variety of plates and shells precludes their inclusion here.

Two comprehensive indexes are provided, a subject index and a Code sec­tion reference index. The user wishing to locate all Code references to a partic­ular subject, as well as the user interested in the interpretation of a particular Code section, should find this arrangement most convenient. Commentary sec­tions referenced in the text are listed in a third index.

Inch-pound units are used throughout this Guide-consistent with the inch­pound version of the 1995 ACI Building Code. At press time, federal govern­ment-funded construction projects were required to be designed in metric units and built with metric materials. Construction projects in the private sector are not mandated to be metric. Some of the metric aspects of reinforced concrete design and construction are briefly discussed in Appendix A of this Guide.

Artwork for the book was prepared by Jesse Trevino. His skillful production of the drawings and charts is greatly appreciated by the authors.

The late Paul Rice originated the concept of this Guide. His vision, plus the participation and contributions of co-author Hoffman, culminated in the first edition of the Guide, which was published in 1973. The second edition under the stewardship of Rice and Hoffman followed in 1979. For the third edition in 1985, the senior authors were augmented with the addition of Gustafson and Gouwens. Although a quarter of a century has passed since the first edition was published, this fourth edition follows the style and format as envisioned and fostered by Rice. Paul Rice's legacy has inspired us to follow through with the preparation of this new edition, and we gratefully dedicate this book to his memory.

Edward S. Hoffman David P. Gustafson Albert J. Gouwens

Contents

Preface / v

1 Structural Materials, Specifications, and Testing / 1

2 Structural Analysis and Design-General/15 3 One-way Reinforced Concrete Slabs / 37

4 One-way Joist Systems / 55 5 Two-way Solid Flat Plate Design / 76

6 Two-way Solid Flat Slab Design /142 7 Two-way (Waffle) Flat Slab Design /178

8 Two-way Slab-Beam Design /203 9 Beams and Girders / 216

10 Columns / 266 11 Walls /324

12 Footings /336

13 Splices and Details of Reinforcement / 354 14 Prestressed Concrete / 388 15 Structural Lightweight Aggregate Concrete / 419

16 Structural Plain Concrete /423

17 Field Inspection and Construction / 432

18 Strength Evaluation of Existing Structures /437 Appendix A Metrication / 444 Subject Index / 453

Code Section Index / 459

Commentary Section Index / 461