2018 National Design Specification - AWC

1 By downloading this file to your computer, you are accepting and agreeing to the terms of AWC's end-user license agreement (EULA), which may be viewed here: End User License Agreement. Copyright infringement is a violation of federal law subject to criminal and civil penalties. 2018. E D I T I O N. NDS.. National Design Specification . for Wood Construction AMERICAN. WOOD. APPROVED. NOVEMBER 16, 2017 COUNCIL. Updates and Errata While every precaution has been taken to ensure the accuracy of this document, errors may have occurred during development. Updates or Errata are posted to the American Wood Council website at Technical inquiries may be addressed to On behalf of the industry it represents, AWC is committed to ensuring a resilient, safe, and sustainable built environment. To achieve these objectives, AWC contributes to the development of sound public policies, codes, and regulations which allow for the appropriate and responsible manufacture and use of wood products.

2 We support the utilization of wood products by developing and disseminating consensus standards, comprehensive technical guidelines, and tools for wood Design and construction, as well as providing education regarding their application. 2018. E D I T I O N. NDS.. National Design Specification . for Wood Construction AMERICAN. WOOD. COUNCIL. APPROVED. NOVEMBER 16, 2017. ii National Design Specification FOR WOOD CONSTRUCTION. National Design Specification (NDS) for Wood Construction 2018 Edition First Web Version: November 2017. ISBN 978-1-940383-42-2. Copyright 2017 by American Wood Council All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including, without limitation, electronic, optical, or mechanical means (by way of example and not limitation, photocopying, or recording by or in an information storage retrieval system) without express written permission of the American Wood Council.

3 For information on permission to copy material, please contact: Copyright Permission American Wood Council 222 Catoctin Circle, SE, Suite 201. Leesburg, VA 20175. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL. National Design Specification FOR WOOD CONSTRUCTION iii FOREWORD. The National Design Specification for Wood tion , relating to the designer's responsibility to Construction (NDS ) was first issued by the Na- make adjustments for particular end uses of structures. tional Lumber Manufacturers Association (now the Since the first edition of the NDS in 1944, the American Wood Council) (AWC) in 1944, under the Association's Technical Advisory Committee has title National Design Specification for Stress-Grade continued to study and evaluate new data and devel- Lumber and Its Fastenings. By 1971, the scope of opments in wood Design .

4 Subsequent editions of the the Specification had broadened to include additional Specification have included appropriate revisions to wood products. In 1977, the title was changed to provide for use of such new information. This edi- reflect the new nature of the Specification , and the tion incorporates numerous changes considered by content was rearranged to simplify its use. The 1991 AWC's ANSI-accredited Wood Design Standards edition was reorganized in an easier to use equation Committee. The contributions of members of this format , and many sections were rewritten to provide Committee to improvement of the Specification as a greater clarity. National Design standard for wood construction are In 1992, the American Forest & Paper Association especially recognized. (AF&PA) formerly the National Forest Products Acknowledgement is also made to the Forest Association was accredited as a canvass sponsor by Products Laboratory, Department of Agriculture, the American National Standards Institute (ANSI).

5 For data and publications generously made avail- The Specification subsequently gained approval as an able, and to the engineers, scientists, and other users American National Standard designated ANSI/NFoPA who have suggested changes in the content of the NDS-1991 with an approval date of October 16, 1992. Specification . AWC invites and welcomes comments, In 2010, AWC was separately incorporated, re- inquiries, suggestions, and new data relative to the chartered, and accredited by ANSI as a standards provisions of this document. developing organization. The current edition of the It is intended that this document be used in con- Standard is designated ANSI/AWC NDS-2018 with junction with competent engineering Design , accurate an approval date of November 16, 2017. fabrication, and adequate supervision of construction. In developing the provisions of this Specification , AWC does not assume any responsibility for errors the most reliable data available from laboratory tests or omissions in the document, nor for engineering and experience with structures in service have been designs, plans, or construction prepared from it.

6 Carefully analyzed and evaluated for the purpose of Those using this standard assume all liability aris- providing, in convenient form, a National standard ing from its use. The Design of engineered structures of practice. is within the scope of expertise of licensed engineers, It is intended that this Specification be used in architects, or other licensed professionals for applica- conjunction with competent engineering Design , tions to a particular structure. accurate fabrication, and adequate supervision of American Wood Council construction. Particular attention is directed to Sec- Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL. iv National Design Specification FOR WOOD CONSTRUCTION. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL.

7 National Design Specification FOR WOOD CONSTRUCTION v TABLE OF CONTENTS FOR THE NDS. Part/Title Page Part/Title Page 1 General Requirements for structural 7 Prefabricated Wood 47. 1 General 48. Scope 2 Reference Design Values 48. General Requirements 2 Adjustment of Reference Design Standard as a Whole 2 Values 48. Design Procedures 2 Special Design Considerations 50. Specifications and Plans 3. Notation 3 8 structural Composite 51. General 52. 2 Design Values for structural Reference Design Values 52. 9 Adjustment of Reference Design General 10 Values 52. Reference Design Values 10 Special Design Considerations 54. Adjustment of Reference Design Values 10 9 Wood structural General 56. 3 Design Provisions and Reference Design Values 56. General 14 Adjustment of Reference Design Bending Members General 15 Values 57. Bending Members Flexure 15 Design Considerations 58. Bending Members Shear 17. Bending Members Deflection 19 10 Cross- laminated Compression Members General 20 General 60.

8 Solid Columns 21 Reference Design Values 60. Tension Members 22 Adjustment of Reference Design Combined Bending and Axial Loading 22 Values 60. Design for Bearing 23 Special Design Considerations 62. 4 Sawn 11 Mechanical General 26 General 64. Reference Design Values 27 Reference Design Values 65. Adjustment of Reference Design Adjustment of Reference Design Values 28 Values 65. Special Design Considerations 31 12 Dowel-Type 5 structural glued laminated General 74. General 34 Reference Withdrawal Design Values 76. Reference Design Values 35 Reference Lateral Design Values 83. Adjustment of Reference Design Combined Lateral and Withdrawal Values 36 Loads 89. Special Design Considerations 39 Adjustment of Reference Design Values 89. 6 Round Timber Poles and Multiple Fasteners 93. General 44. Reference Design Values 44 13 Split Ring and Shear Plate Adjustment of Reference Design Values 44 General 120. Reference Design Values 121.

9 Placement of Split Ring and Shear Plate Connectors 127. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL. vi TABLE OF CONTENTS. Part/Title Pag Part/Title Page 14 Timber General 134 A Construction and Design Practices 158. Reference Design Values 134 B Load Duration (ASD Only) 160. Placement of Timber Rivets 136 C Temperature Effects 162. D Lateral Stability of Beams 163. 15 Special Loading E Local Stresses in Fastener Groups 164. Lateral Distribution of a F Design for Creep and Critical Concentrated Load 146 Deflection Applications 169. Spaced Columns 146 G Effective Column Length 171. Built-Up Columns 148 H Lateral Stability of Columns 172. Wood Columns with Side Loads and I Yield Limit Equations for Connections 173. Eccentricity 151 J Solution of Hankinson Formula 176. 16 Fire Design of Wood K Typical Dimensions for Split Ring and General 154 Shear Plate Connectors 179.

10 Design Procedures for Exposed L Typical Dimensions for Dowel-Type Wood Members 154 Fasteners and Washers 180. Wood Connections 156 M Manufacturing Tolerances for Rivets and Steel Side Plates for Timber Rivet Connections 185. N Load and Resistance Factor Design (LRFD) 186. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL. National Design Specification FOR WOOD CONSTRUCTION vii LIST OF TABLES FOR THE NDS. Frequently Used Load Duration Group Action Factors, Cg, for 4 Split Ring Factors, CD .. 11 or Shear Plate Connectors with Wood Side Temperature Factor, Ct .. 11 70. Format Conversion Factor, KF Group Action Factors, Cg, for Bolt or Lag (LRFD Only).. 12 Screw Connections with Steel Side 71. Resistance Factor, (LRFD Only).. 12 Group Action Factors, Cg, for 4 Shear Plate Connectors with Steel Side 72. Effective Length, e, for Bending 16 Lag Screw Reference Withdrawal Design Values, 77.