Significant Changes to AWC s Special Design Provisions for Wind and Seismic

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1 Significant Changes to AWC s Special Design Provisions for Wind and Seismic Michelle Kam-Biron, PE, SE, SECB Director of Education American Wood Council Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of AWC is prohibited. American Wood Council rights reserved. 1

2 The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516 Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non AIA members are available upon request. This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. 3 Course Description AWC's 2015 Special Design Provisions for Wind and Seismic (SDPWS) standard is referenced in US building codes and used to design wood structures worldwide. The current edition, designated ANSI/AWC SDPWS-2015, were approved as ANSI American National Standards in This presentation will provide an overview of changes in the 2015 SDPWS relative to previous editions that include shear walls and diaphragms.. 4 rights reserved. 2

3 Objectives Upon completion, participants will understand: 1. Discuss significant changes between the 2008 and 2015 SDPWS. 2. Be able to identify and discuss background behind the significant changes. 3. Be able to identify the lateral resisting systems and undwerstand where to obtain design provisions for these systems. 4. Discuss the overall format and content within the 2015 SDPWS. 5 Outline Overview NDS SDPWS Chapter-by-chapter discussion Changes from previous editions SDPWS Summary More Info 6 rights reserved. 3

4 NDS History Governing Codes for Wood Design 2015 NDS referenced in 2015 IBC 8 rights reserved. 4

5 ANSI Accreditation AWC ANSI-accredited standards developer Consensus Body Wood Design Standards Committee 9 Outline Overview NDS SDPWS Chapter-by-chapter discussion Changes from previous editions SDPWS Summary More Info 10 rights reserved. 5

6 2015 NDS Primary Change New Provisions to Address CLT Charging Language Design Values Design Equations Product Chapter Connection Design Fire Design NDS Chapter Reorganization 2012 NDS 1-3 General 4-9 Products Connections 14 Shear Walls & Diaphragms 15 Special Loading 16 Fire 2015 NDS 1-3 General 4-10 Products +CLT Connections Shear Walls & Diaphragms 15 Special Loading 16 Fire 12 rights reserved. 6

7 NDS 2015 Chapters 1. General Requirements for Building Design 2. Design Values for Structural Members 3. Design Provisions and Equations 4. Sawn Lumber 5. Structural Glued Laminated Timber 6. Round Timber Poles and Piles 7. Prefabricated Wood I-Joists 8. Structural Composite Lumber 9. Wood Structural Panels 10. Cross-Laminated Timber 11. Mechanical Connections 12. Dowel-Type Fasteners 13. Split Ring and Shear Plate Connectors 14. Timber Rivets 15. Special Loading Conditions 16. Fire Design of Wood Members 13 NDS 2015 Supplement 1. Sawn Lumber Grading Agencies 2. Species Combinations 3. Section Properties 4. Reference Design Values Sawn Lumber and Timber MSR and MEL Decking Non-North American Sawn Lumber Structural Glued Laminated Timber Timber Poles and Piles 14 rights reserved. 7

8 NDS 2015 Appendices A. Construction and Design Practices B. Load Duration (ASD Only) C. Temperature Effects D. Lateral Stability of Beams E. Local Stresses in Fastener Groups F. Design for Creep and Critical Deflection Applications G. Effective Column Length H. Lateral Stability of Columns I. Yield Limit Equations for Connections J. Solution of Hankinson Equation K. Typical Dimensions for Split Ring and Shear Plate Connectors L. Typical Dimensions for Standard Hex Bolts, Hex Lag Screws, Wood Screws, Common, Box, and Sinker Nails M. Manufacturing Tolerances for Rivets and Steel Side Plates for Timber Rivet Connections N. Appendix for Load and Resistance Factor Design (LRFD) Mandatory 15 Outline Overview NDS SDPWS Chapter-by-chapter discussion Changes from previous editions SDPWS Summary More Info 16 rights reserved. 8

9 Code Acceptance of Standard 2012 IBC References 2008 SDPWS in Section 2305 for lateral design and construction 2015 IBC References 2015 SDPWS in Section 2305 for lateral design and construction General Overview Outline Chapter 1: Flowchart Chapter 2: General Design Requirements Chapter 3: Members and Connections Chapter 4: Lateral Force Resisting Systems rights reserved. 9

10 Chapter 1 Designer Flowchart Chapter 1 Designer Flowchart rights reserved. 10

11 Chapter 2 General Requirements Chapter 2 General Requirements General Terminology Notation rights reserved. 11

12 Chapter 2 General Requirements Terminology Definitions New Flexible and Rigid Diaphragm removed Chapter 3 - Members and Connections rights reserved. 12

13 Chapter 3 - Members and Connections Framing Sheathing Connections Covers out-of-plane wind load resistance of shear walls and diaphragms 26 Chapter 3 - Members and Connections Framing walls Accounts for composite action Strength and Stiffness Applies now to EI Up to 24 oc New Extension of 1.15 repetitive member factor, C r 27 rights reserved. 13

14 Chapter 3 - Members and Connections Sheathing capacities - walls Revised 28 Chapter 3 - Members and Connections Sheathing capacities roof Revised 29 rights reserved. 14

15 Chapter 3 - Members and Connections Uplift Resisting Systems New Chapter 3 - Members and Connections 3.4 Uplift Force Resisting Systems New rights reserved. 15

16 Chapter 4 - Lateral Force-Resisting Systems Chapter 4 - Lateral Force-Resisting Systems General Wood Diaphragms Wood Shear Walls Covers in-plane wind and seismic load resistance of shear walls and diaphragms 33 rights reserved. 16

17 Chapter 4 - Lateral Force-Resisting Systems Diaphragms 34 Chapter 4 Anchorage of Concrete or Masonry Walls Anchorage of Concrete or Masonry Walls to Diaphragm SDC C, D, E, or F New 40 rights reserved. 17

18 Chapter 4 Anchorage of Concrete or Masonry Walls Source: APA 41 Chapter 4 Anchorage of Concrete or Masonry Walls Pre-fabricated roof sections lifted into place Safety, cost, speed Two common types All wood Hybrid 42 rights reserved. 18

19 Subdiaphragm and Continuous Ties 43 Chapter 4 - Lateral Force-Resisting Systems Wood Diaphragms a) b) 44 rights reserved. 19

20 Chapter 4 Anchorage of Concrete or Masonry Walls Source: WoodWorks 45 Chapter 4 Anchorage of Concrete or Masonry Walls 46 rights reserved. 20

21 Irregularity Collector forces likely comply with exception per ASCE Sec Exception to Overstrength 48 rights reserved. 21

22 Exception to Overstrength 49 Irregularity Reentrant Corner Collector Collector 50 rights reserved. 22

23 Irregularity 51 Chapter 4 - Lateral Force-Resisting Systems Wood Diaphragms Anchor bolting of ledger : Design for 25% more shear 52 rights reserved. 23

24 Chapter 4 - Lateral Force-Resisting Systems Wood Diaphragms Collector beam Boundary nail (B.N.) diaphragm NOT subject to 25% increase 53 Chapter 4 Nominal Design Value Revised rights reserved. 24

25 Chapter 4 Nominal Design Value Diaphragm Configuration Figures Direction with respect to load of Continuous panel joints Framing members Independent of panel orientation Revised Chapter 4 Horizontal Distribution Revised Horizontal Distribution of Shear Idealized as Flexible ASCE , or DIAPHRAGM > 2 x SHEARWALLS tributary area Idealized as Rigid ASCE , or DIAPHRAGM <2 x SHEARWALLS relative lateral stiffness of vertical LFRS Semi-rigid complex analysis or envelope (NEW) 56 rights reserved. 25

26 Chapter 4 - Lateral Force-Resisting Systems Torsional Irregularity Torsional Irregular Story Drift A max > 1.2 A & B Average 57 Chapter 4 - Lateral Force-Resisting Systems Revised Torsional Irregularity SDC A - Exempt Rigid or Semi-rigid Conform to Diaphragm Assemblies , or WSP diaphragms L/W < 1.5:1 Diagonal Lumber (single or double layer) L/W < 1:1 A max < ASCE 7 allowable story drift 58 rights reserved. 26

27 Chapter 4 Open Front Structures Revised 59 Chapter 4 Open Front Structures Revised Open Front Structures Conform to Diaphragm Assemblies , or Not Torsionally Irregular WSP diaphragms L /W < 1.5:1 Diagonal Lumber (single or double layer) L /W < 1:1 Torsionally Irregular > 1-story L /W < 0.67:1 1-story L /W < 1:1 60 rights reserved. 27

28 Chapter 4 Open Front Structures Revised Open Front Structures Load parallel to opening - model as semi-rigid or rigid A max < ASCE 7 allowable story drift L < 35 Exception: Cantilever < 6 beyond nearest vertical LFRS need not comply to Chapter 4 Open Front Structures Revised Open Front Structures 1 story L < 25 L /W < 1:1 Idealized as rigid - distribution of torsional shear rights reserved. 28

29 Chapter 4 Open Front Structures 63 Chapter 4 High Load Diaphragms Consistent with IBC 2006 Includes apparent shear stiffness (G a ) Table 4.2B Nominal Unit Shear Capacities for Blocked Wood-Frame Diaphragms Utilizing Multiple Rows of Fasteners (High Load Diaphragms) 64 rights reserved. 29

30 Chapter 4 High Load Diaphragms Blocked Diaphragm Configuration Figures Direction with respect to load of Continuous panel joints Framing members Independent of panel orientation Revised High Load Diaphragms rules for construction Need 3" or greater nominal members Requires Special Inspection rights reserved. 30

31 Chapter 4 High Load Diaphragms High Load Blocked Diaphragms 4. The depth of framing members and blocking into which the nail penetrates shall be 3" nominal or greater The width of the nailed face of framing members and blocking at boundaries and adjoining panel edges shall be 3" nominal or greater. The width of the nailed face not located at boundaries or adjoining panel edges shall be 2" nominal or greater. High Load Diaphragms Boundary and panel edge nailing details rights reserved. 31

32 Chapter 4 High Load Diaphragms Avoid Nail Splitting Source: John Lawson, S.E., Kramer and Lawson Chapter 4 - Lateral Force-Resisting Systems Shear Walls 70 rights reserved. 32

33 Chapter 4 - Lateral Force-Resisting Systems Wood Shear Walls Chapter 4 - Lateral Force-Resisting Systems Structural Fiberboard Shear Walls NEW rights reserved. 33

34 Chapter 4 Nominal Design Value Wind nominal unit shear capacity v w Legacy IBC allowable stress design value x 2.8 Seismic nominal unit shear capacity v s v s = v w / Chapter 4 Design Value Format Nominal design values tabulated for shear walls ASD reduction factor (2.0) LRFD resistance factor (0.80) rights reserved. 34

35 Chapter 4 - Lateral Force-Resisting Systems Shears Walls in a Line: same materials and construction Individual full height shear walls provide all same deflection sw 75 Chapter 4 - Lateral Force-Resisting Systems Shears Walls in a Line: same materials and construction Individual full height shear walls provide all same deflection sw REVISED Exception: WSP h/b s > 2:1 v s x 2b s /h Fiberboard h/b s > 1:1 v s x ( b s /h) Shear distribution proportional to capacities Shear capacity reduction not combined with 2:1 unless v s = 2(b s /h) aspect ratio adjustment ( ) 2:1 3:1 3½: rights reserved. 35

36 Chapter 4 - Lateral Force-Resisting Systems Wood Shear Walls Chapter 4 Aspect Ratios & Capacity Adjustments Revised Shear Wall Aspect Ratio Factors h/b s > 2:1 WSP v s x ( h/b s ) h/b s > 1:1 Struct. Fiberboard v s x ( h/b s ) 2:1 unless v s = ( (h/b s )) 2:1 3:1 3½: rights reserved. 36

37 Chapter 4 Aspect Ratios & Capacity Adjustments Revised Perforated Shear Walls h/b s > 3.5:1 Not considered h/b s > 2:1 L i = L (2b s /h) Aspect Ratio Factors ( ) do not apply Shear distribution exceptions ( ) do not apply Chapter 4 Aspect Ratios & Capacity Adjustments Force-transfer Shear Walls h/b s > 3.5:1 Not considered rights reserved. 37

38 Chapter 4 Construction Requirements NEW Common Framing Members 2-2x permitted to replace 3x Fastened together per NDS Spacing <4 o.c. shall be staggered Applies broadly to all framing Shear Wall Systems 2-2x permitted to replace 3x Wood Structural Panels ( (5)) Particleboard ( (5)) 83 What s Missing for CLT? Seismic Design! ASCE 7 Minimum Design Loads for Buildings and Other Structures Response Modification Coefficient, R CLT not recognized system in ASCE 7 Table Options Performance-based design procedure per ASCE 7 Demonstrating equivalence to an existing ASCE 7 system ASCE 7-10, FEMA P695, and FEMA P795 Quantification of Building Seismic Performance Factors; Component Equivalency Methodology 84 rights reserved. 38

39 Outline Overview NDS SDPWS Chapter-by-chapter discussion Changes from previous editions SDPWS More Info 85 Availability PDF versions Free view-only Buy a printable PDF Winter 2015 Commentary Printed version 86 rights reserved. 39

40 Technical Articles Structure Magazine 2015 NDS January SDPWS July 2015 Wind & Seismic Standards More details on changes Wood Design Focus papers 2008 Special Design Provisions for Wind and Seismic Use of Wood Structural Panels to Resist Combined Shear and Uplift from Wind 2015 National Design Specification for Wood Construction Download free at rights reserved. 40

41 Questions? Michelle Kam-Biron, PE, SE, SECB Director of Education 89 rights reserved. 41