Structural CLT Floor and Roof Design Scott Breneman, PhD, PE, SE Senior Technical Director Project Resources and Solutions Division WoodWorks Wood Products Council Photo Ema Peter Photography 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. scott.breneman@woodworks.org 1
Course Description This presentation is intended for designers of building systems seeking to familiarize themselves with the category of products known as mass timber, and specifically cross laminated timber (CLT). Topics will include manufacturing and product performance standards, structural design standards, and recognition of CLT in the International Building Code. Specific attention will be given to the design of CLT in horizontal applications i.e., as panels of floor and roof systems and discussion will include how to address important serviceability requirements related to deflection and floor vibration design. Example projects and details will be presented to highlight possible applications of CLT in building structures. Learning Objectives 1. Discuss product manufacturing and design standards relevant to cross laminated timber (CLT), and identify where these standards are recognized in the International Building Code. 2. Consider the structural design properties of CLT relevant to floor and roof applications. 3. Discover how to design CLT floors to achieve serviceability goals related to deflection and vibration. 4. Examine the use of CLT in example buildings and connection details. scott.breneman@woodworks.org 2
Introduction Wood Building Systems Post and Beam Light Frame Mass Timber scott.breneman@woodworks.org 3
Mass Timber Products Nail Laminated Timber (NLT) Glue Laminated Timber (GLT) Glulam Beams & Columns Laminated Veneer Lumber (LVL) Massive Plywood Panels (MPP) Cross Laminated Timber (CLT) Images Source: Structurecraft Mass Timber Products Cross-laminated timber (CLT) 8 scott.breneman@woodworks.org 4
Cooley Landing Education Center East Palo Alto, CA Photo: Arbor Building Group Photos: WoodWorks Cooley Landing Education Center East Palo Alto, CA scott.breneman@woodworks.org 5
Albina Yard Portland, OR Photo Credit: LEVER Architecture Albina Yard Portland, OR Photo Credit: WoodWorks scott.breneman@woodworks.org 6
Albina Yard Portland, OR 4 stories 16,000 sf Green Roof ARCHITECT: Lever Architecture 13 Photo: Scott Breneman Albina Yard Portland, OR ARCHITECT: Lever Architecture 14 Photo: Scott Breneman scott.breneman@woodworks.org 7
Redstone Arsenal Hotel Huntsville, AL Image Credit: Lend Lease Redstone Arsenal Hotel 62,600 sf, 4 story hotel, 92 private rooms CLT used for walls, roof panels, and floor panels 1,557 CLT Panels; Typical floor panel is 8 x50 Completed Late 2015 Photos: Lend Lease, IHG Hotels, & Schaefer scott.breneman@woodworks.org 8
2017 TallWood House at Brock Commons University of British Columbia Vancouver, Canada 18 Stories (17+1) 174 Feet tall Beamless two-way CLT floor slab ARCHITECT: Acton Ostray ENGINEER: Fast & Epp Cross Laminated Timber Considerations: Large light-weight panels Dimensionally stable Precise CNC machining available Recognized by IBC Dual Directional span capabilities Often architecturally exposed Fast on-site construction Graphic Credit: StructureCraft scott.breneman@woodworks.org 9
SB31 CLT History Timeline Europe North America 1990 2000 2005 2010 2015 Austria industryacademia joint research Significantly increased use in Europe interest began 2010 1 st Production 2011- PRG320 2011 -Canadian Handbook 2013 US Handbook.3 million m 3 of built CLT projects Recognized in 2015 IBC.6-1 million m 3 of built CLT projects CLT Product Standardization scott.breneman@woodworks.org 10
What is CLT? 3+ layers of laminations Typically Solid Sawn Laminations Cross-Laminated Layup Thickness 3 to 20 inches* Max Length 24 to 60 feet* Max Width 8 to 10 feet* *All dimensions are approximate. Consult with manufacturers First Tech Credit Union, Hillsboro, Oregon Photo Credit: Structurlam Products scott.breneman@woodworks.org 11
North American CLT Product Standard The Standard Covers: - U.S. and Canada Use - Panel Dimensions and Tolerances - Component Requirements - Structural Performance Requirements - Panel and Manufacturing Qualification - Marking (Stamping) - Quality Assurance ANSI/APA PRG 320 Standard for Performance-Rated Cross-Laminated Timber CLT Stress Grades Stress Grade Major Strength Direction Minor Strength Direction E1 1950f-1.7E MSR SPF #3 Spruce Pine Fir E2 1650f-1.5E MSR DFL #3 Doug Fir Larch E3 1200f-1.2E MSR Misc #3 Misc E4 1950f-1.7E MSR SP #3 Southern Pine V1 #2 Doug Fir Larch #3 Doug Fir Larch V2 #1/#2 Spruce Pine Fir #3 Spruce Pine Fir V3 #2 Southern Pine #3 Southern Pine Standard (Non-mandatory) CLT stress grade in PRG 320-2012. Other custom stress grades including structural composite lumber (SCL) permitted scott.breneman@woodworks.org 12
Common CLT Layups 3-ply 3-layer 5-ply 5-layer 7-ply 7-layer 7-ply 5-layer 9-ply 9-layer 9-ply 7-layer PRG 320 Defined Layups scott.breneman@woodworks.org 13
3 rd Party Product Certification of CLT CLT Product Reports Stress Grade (standard or custom) Layup (standard or custom) Panel Properties scott.breneman@woodworks.org 14
Structural Design Standardization National Design Specification for Wood Construction 2015 Edition Model Building Code Acceptance 2015 International Building Code scott.breneman@woodworks.org 15
SB9 CLT is Defined 2015 IBC SB16 SB17 Highlights of CLT Provisions in IBC 2015 CLT is generally available for use in Type III, IV and V construction. IBC 2015 Chapter 6 Defines Dimensions of CLT to qualify as Heavy Timber (Type IV Construction) 6 Walls 4 Floors 3 Roofs Non Fire-Retardant Treated CLT allowed in Exterior Walls of Type IV construction in many conditions. (IBC 2015 602.4) The Heavy Timber construction size requirements only apply to Type IV Construction scott.breneman@woodworks.org 16
CLT Manufactures for use in the US to PRG-320 DR Johnson Lumber, Oregon KLH USA, Subsidiary of KLH Massivholz, Austria. Nordic Structures, Quebec, Canada SmartLam, Columbia Fall, Montana Structurlam, British Columbia, Canada Working with CLT: Know Your Supply Chain CLT Manufactures different CLT grades and maximum panel sizes CLT Manufacturers have specific CNC capabilities 3 rd Party Fabricators can have additional CNC capabilities Photo: DR Johnson Photo: Sauter Timber scott.breneman@woodworks.org 17
Working with CLT: Communicate Your Requirements Define the deliverables you need from the supplier: - Shop drawings - Shop drawings with Engineering Stamp - Engineered Drawings and Calculations (e.g. as a deferred submittal) Structural Properties scott.breneman@woodworks.org 18
Structural Section Properties Non-homogenous, anisotropic material FLATWISE Panel Loading Span in MAJOR Strength Direction Parallel Direction Span in MINOR Strength Direction Perpendicular Direction Reference & Source: ANSI/APA PRG 320-2017 scott.breneman@woodworks.org 19
EDGEWISE Panel Loading Span in MAJOR Strength Direction Span in MINOR Strength Direction Reference & Source: ANSI/APA PRG 320-2017 Flatwise Flexural Strength Design properties based on an Extreme Fiber Model: Flexural Capacity Check: Mb M b (F b S eff ) Bending Stress M b = applied bending moment (F b S eff ) = adjusted bending capacity S eff F b = effective section modulus = reference bending design stress of outer lamination Reference: NDS 2015 scott.breneman@woodworks.org 20
Flatwise Flexural Strength Flexural Capacity Check (ASD) Mb Bending Stress (F b S eff ) = C D C M C t C L (F b S eff ) per NDS Commonly 1.0 M b C D (1.0) (F b S eff ) Provided as combined value Reference: NDS 2015 Flatwise Flexural Strength Design Example Select acceptable CLT section Given: 16 foot span floor 40 psf live load, 40 psf total dead load. Assume: one-way spanning action in major axis of CLT Analysis of a 1 ft strip of panel as beam Calculate ASD Dead + Live Applied Moment M b = w L 2 / 8 = (40+40psf) (16ft) 2 / 8 = 2560 lb-ft/ft 40 psf DL, 40 psf LL 16 foot span scott.breneman@woodworks.org 21
Flatwise Flexural Strength Design Example Look for Acceptable CLT Grade from PRG 320: F b S eff,0 > 2560 lb-ft/ft 4,800 Select 5-Ply 6 7/8 Thick V1 Panel with F b S eff,0 = 4800 lb-ft/ft Reference: ANSI/APA PRG 320-2012 Flatwise Flexural Strength Design Example 40 psf DL, 40 psf LL ASD Flexural Capacity: Dead + Live load, C D = 1.0 (F b S eff ) = C D (1.0) (F b S eff ) = 1.0 (1.0) (4800 lb-ft/ft) = 4800 lb-ft/ft 16 foot span M b = 2560 lb-ft/ft (F b S eff ) = 4800 lb-ft/ft Flexural Strength OK scott.breneman@woodworks.org 22
Flatwise Shear Strength Design Properties based on Extreme Fiber Model: Shear Capacity Check: V a F s (Ib/Q) eff V a = applied shear F s (IbQ eff ) = adjusted shear strength Shear Stress V a Jargon Alert! AKA Planar Shear, Out-of-Plane Shear, or Rolling Shear Strength Reference: NDS 2015 Wood Structural Panel Term Structural Engineering Term CLT Term Flatwise Shear Strength Design Properties based on Extreme Fiber Model: Shear Capacity Check (ASD): V planar Shear Stress F s (IbQ) eff = C M C t (F s (IbQ) eff ) = C M C t V s Commonly 1.0 V planar (1.0) V s From Manufacturer Note: Duration of Load Effects (Cd and λ) NOT applicable to Flatwise Shear Strength in the NDS Reference: NDS 2015 & Product Reports scott.breneman@woodworks.org 23
Shear Force Terminology Source: ANSI/APA PRG 320-2017 Planar Shear Rolling Shear Shear-In-the-Plane? Out-of-plane forces? FLATWISE Shear in PRG 320 2017 Source: NDS 2015 Manual NDS 2015: F s (Ib/Q) eff PRG 320 Product Reports: V s,0 & V s,90 Flatwise Shear Strength Rolling Shear Source: CSA O86-14, 2016 Supplement scott.breneman@woodworks.org 24
Shear Force Terminology & Jargon Source: ANSI/APA PRG 320-2017 Source: NDS 2015 Manual Through-the-Thickness Shear In-plane Shear Forces EDGEWISE Shear in PRG 320-2017 NDS 2015: F v (t v ) PRG 320-2017: F v,e,0 t p & F v,e,90 t p Flatwise Flexural Stiffness Shear Analogy Method EI eff Bending Stress Reference: US CLT Handbook Chapter 3 scott.breneman@woodworks.org 25
Flatwise Flexural Stiffness EI eff GA eff Flatwise Flexural Stiffness Important EI eff to develop properties of new CLT Sections. Not to use standard CLT Sections GA eff scott.breneman@woodworks.org 26
Flatwise Flexural Stiffness EI Advanced eff Use: Calculating Structural Capacities under Fire Conditions using NDS 2015 Chapter 16 GA eff Flatwise CLT Panel Section Properties Flexural Strength: Flexural Stiffness: F b S eff,0 EI eff,0 F b S eff,90 EI eff,90 Shear Strength: V s,0 Shear Stiffness: GA eff,0 V s,90 GA eff,90 Values in RED provided by CLT manufacturer Reference: PRG 320 and CLT Product Reports scott.breneman@woodworks.org 27
Using PRG 320 Standard Grades for Design? PRG 320 includes pre-defined Stress Grades, Layups and related Design Properties Is doesn t tell you what CLT grades and layups are available. Coordinate your design with manufactures availability and information Deflection Calculations General Purpose: 1 Way, Beam Action Needed Stiffness: EI eff,0 GA eff,0 Can model multiple spans, cantilevers, etc. scott.breneman@woodworks.org 28
Example Deflection Calculations Example Calculation: w = 80 psf Uniform loading on one way slab: Beam Analysis using Flexural Stiffness: EI eff,0 Shear Stiffness: 5/6 GA eff,0 Maximum Deflection @ Mid-Span 16 foot span 5/6 GA eff Design Example: = 0.284 in + 0.034 in = 0.318 in = L / 604 Deflection Creep Factor Deformation to Long Term Loads Δ " =$ %& Δ (" +Δ *" NDS Eq 3.5-1 Δ *" Δ (" $ %& Deflection due to short-term loading Immediate deflection due to long term loading 2.0 for CLT in dry service conditions Design Example: ST from 40psf = 0.159 in LT from 40psf = 0.159 in T = 2.0 (0.159) + 0.159 = 0.477 in = L / 403 Reference: NDS 2015 w = 40 + 40 psf 16 foot span scott.breneman@woodworks.org 29
Deflection Calculations Simplified Beam Deflections: Given load pattern and support conditions: Uniform load, w 5/6 GA eff Span, L Find Apparent Flexural Stiffness, EI app, such that EI app +, -.. = Reference: US CLT Handbook +, /00 1 + 11.5+, /00 45 /00 6 7 Deflection Calculations Simplified Beam Deflections For single span, simple loading patterns, Apparent Flexural Stiffness, EI app, to determine maximum (mid-span) deflection: +, -.. = +, /00 +, /00 +, -.. = 1+ 16$ 9, /00 1+ $ 9+, /00 45 5 /00 6 7 /00 6 7 NDS 2015 US CLT Handbook & NDS 2015 Commentary For Major Axis Spans:, /00 = +, /00 ; +: 5 /00 = 45 /00 4 : Reference: US CLT Handbook & NDS 2015 4 : = + : 16 scott.breneman@woodworks.org 30
Deflection Calculations Simplified Beam Deflections For single span, simple loading patterns, Apparent Flexural Stiffness, EI app, to determine maximum (mid-span) deflection: +, -.. = +, /00 1+ $ 9+, /00 45 /00 6 7 +, -.. = +, /00 1+ 16$ 9, /00 5 /00 6 7 Apparent Flexural Stiffness depends on Span Length L 1 = 20 foot +, -.. = +, -.. 7 L 2 = 16 foot Deflection Calculations General Purpose, 2 Way, Plate Action Flexural Stiffness EI eff,0 Shear Stiffness: EI eff,90 5/6 GA eff,0 5/6 GA eff,90 5/6 from A = 5/6 A shape factor for rectangular sections scott.breneman@woodworks.org 31
Floor Vibration Occupant perception of vibration is a highly recommended design consideration. One approach: US CLT Handbook, Chapter 7 (FPI Method) Calculated natural frequency of simple span of bare CLT: Where:?= 2.188 +, -.. 26 7 "5 EI app = apparent stiffness for 1 foot strip, pinned supported, uniformly loaded, simple span (K s = 11.5) (lb-in 2 ) ρ = specific gravity of the CLT A = the cross section area (thickness x 12 inches) (in 2 ) Reference: US CLT Handbook, Chapter 7 Floor Vibration FPI Method Recommends Limiting CLT Floor Span such that Frequency f > 9.0 Hz Based on: - Un-topped CLT - Simple span - Bearing wall supports. Span L Does not account for: - Supporting beam flexibility - Multi-span conditions - Additional floor mass (topping slab, etc) Recommend for preliminary sizing only Reference: US CLT Handbook, Chapter 7 scott.breneman@woodworks.org 32
Floor Vibration CLT Handbook, Chapter 7 Recommendations Experimental Verification Results Static Deflection (inch) 0.07 0.06 0.05 0.04 0.03 0.02 Criterion ( f/d^0.7>125.1) Unacceptable Marginal Acceptable 0.01 0 0 5 10 15 Fundamental Natural Frequency (Hz) 20 Research by Lin Hu, et al. at Floor Vibration FPI Method Recommends Limiting CLT Floor Span such that Frequency f > 9.0 Hz Span L Recall: Using spreadsheet & iterate: 1) Estimate L 2) Calculate EI app 3) Calculate L limit 4) Repeat until converges OR Values provided by Manufacturers, et al. Reference: US CLT Handbook, Chapter 7 scott.breneman@woodworks.org 33
Floor Vibration FPI Method Recommends Limiting CLT Floor Span such that: Frequency f > 9.0 Hz Span L 16 Foot Simple Span Design Example: 5-Ply V1 CLT Layup previously selected: EI eff,0 = 415x10 6 lbf-in 2 /ft Converged solution: EI app,0 = 375.9x10 6 lbf-in 2 /ft f = 11.0 Hz max L = 17.03 ft > 16 ft Span meets recommended limit. Probably OK performance. Reference: US CLT Handbook, Chapter 7 FPI Span Limit for Standard Grades / Layups Grade Layup Thickness FPI Span Limit E1 3ply 4 1/8 12 5 E1 5ply 6 7/8 17 4 E1 7ply 9 5/8 21 8 E2 3ply 4 1/8 12 0 E2 5ply 6 7/8 16 8 E2 7ply 9 5/8 20 10 E3 3ply 4 1/8 11 7 E3 5ply 6 7/8 16 1 E3 7ply 9 5/8 20 1 E4 3ply 4 1/8 12 2 E4 5ply 6 7/8 17 0 E4 7ply 9 5/8 21 3 Approximate FPI Span Limits: 3-ply: 11 to 12 ft 5-ply: 16 to 17 ft 7-ply: 20 to 21 ft Grade Layup Thickness FPI Span Limit V1 3ply 4 1/8 12 2 V1 5ply 6 7/8 17 0 V1 7ply 9 5/8 21 3 V2 3ply 4 1/8 11 11 V2 5ply 6 7/8 16 8 V2 7ply 9 5/8 20 10 V3 3ply 4 1/8 12 0 V3 5ply 6 7/8 16 9 V3 7ply 9 5/8 21 0 Approximate FPI Span Limits: - Not for final design: - Does not account for strength or deflections - Does not account for project specifics - Vibrations can be felt by the client. Sharpen your pencil! scott.breneman@woodworks.org 34
Alternative Vibration Criteria Alternative: Use acceptance criteria which address low frequency floors and alternative support configurations. Calibration of dynamic modeling with physical testing valuable SB10 Possible Alternative Vibration Criteria AISC Design Guide 11, Velocity Criteria (Chapter 6 & 7) Example Acceptance Criteria: (good performance) 16,000 µ-in/sec (mips) response to moderate walking in living areas 8,000 µ-in/sec (mips) response to slow walking pace in sleeping areas. AISC DG 11 suggests approximate velocity limit of human perception 8,000 µ-in/sec at 8 Hz and above. AISC Design Guide 11 not for dynamic modeling of CLT floors scott.breneman@woodworks.org 35
SB23 Possible Alternative Vibration Criteria A common European CLT Floor Design Method: a) Static deflection to 1 kn point load > 0.25 mm b) Keep fundamental frequency > 8 Hz OR Fundamental frequency > 4.5 Hz + additional acceleration investigation and limits For more information see: - Floor Vibrations New Results Hamm, Richter & Winter, 2010 - Cross-Laminated Timber Structural Design. Basic design and engineering principles according to Eurocode. proholz Austria, 2014 Edgewise Structural Properties scott.breneman@woodworks.org 36
EDGEWISE Panel Loading Span in MAJOR Strength Direction Span in MINOR Strength Direction Reference & Source: ANSI/APA PRG 320-2017 CLT in Lateral Force Resisting Systems CLT Panels have a significant in-plane shear strength. Source: ICC-ES ESR 3631 ~75 to 195+ PSI Allowable Edgewise Shear ~900 to 2300 PLF per Inch of Thickness. Consult with the Manufacturers for Details Source: APA Product Report PR-L306 Standard test method defined using ASTM D198 scott.breneman@woodworks.org 37
ICC-ES Acceptance Criteria AC 455 Standardizes In-plane Panel Shear Strength for use in Floor and Roof Decks Similar Tests in PRG 320 Standard 2017 Update SB32 EDGEWISE Panel Loading Span in MAJOR Strength Direction Preview of PRG 320-2017 Update Nomenclature Reference Shear Capacity F v,e,0 W p t p Shear Stiffness G e,0 W p t p Reference Flexural Capacity F b,e,0 S e,0 S e,0 = W p 2 t p / 6 Flexural Stiffness E e,0 I e,o I e,0 = W p 3 t p / 12 Source: ANSI/APA PRG 320-2017 scott.breneman@woodworks.org 38
Connection Details SB7 Connection Styles Panel to Panel at floors, roofs or walls Single Surface Spline Half Lap scott.breneman@woodworks.org 39
An Efficient Panel to Panel Connection Self-Tapping Screws as erection bolts ~18 24 o.c 5 ½ to 6 plywood strip ¾ or 1 Thick Nails at spacing required for shear transfer Graphics: ASPECT Structural Engineers Connection Styles Simple connections with: - Metal angles - Self taping Screws and Nails Source: US CLT Handbook scott.breneman@woodworks.org 40
Mass Timber Design Connections Photo Credit: Alex Schreyer Long self tapping screws used extensively throughout mass timber construction 87 Proprietary Products Variety of Self Tapping Screws scott.breneman@woodworks.org 41
SB24 Proprietary Products Source: Simpson Strong-Tie Source: rothoblaas SB22 CLT in NDS 2015 - Connectors Connectors for CLT in NDS 2015: Dowel Type Fasteners, e.g. Lag Screws, Bolts and Nails scott.breneman@woodworks.org 42
CLT in Lateral Force Resisting System CLT in Lateral Force Resisting Systems Source: A Ceccotti in the US CLT Handbook scott.breneman@woodworks.org 43
Connections Determine Lateral Strength Similar to Wood Structural Panel Shear Walls Light frame shear wall strength is dependent on perimeter (edge) nailing Source: SDPWS 2008 Connections Determine Lateral Strength Similar to Wood Structural Panel Shear Walls CLT Shear Strength Depends on Connections Source: US CLT Handbook scott.breneman@woodworks.org 44
CLT Shear Wall Seismic Design Values What R value can I use? Photo: KLH Photo: FPI? CLT Seismic Design CLT Seismic Force Resisting Systems Not addressed In ASCE/SEI 7-10 SDPWS 2015 scott.breneman@woodworks.org 45
Albina Yard Portland Oregon LEVER Architecture KPFF Engineering 4-story office CLT floors and Roof Glulam Gravity Frame Light-Frame Shear Walls Photo: WoodWorks The Bullitt Center Seattle, WA Architect: Miller Hull Partnership Photos Nick Lehoux for the Bullitt Center scott.breneman@woodworks.org 46
T3 Minneapolis Central Core concrete shearwalls Photo Credit: Structurecraft 99 FEMA P-695 Study for CLT Shear Walls Project Lead: John van de Lindt, Colorado State University 4 3 2 1 0-1 -2-3 -4-6 -4-2 0 2 4 6 Modeling Design Method scott.breneman@woodworks.org 47
State of Oregon Statewide Alternative State of Oregon Statewide Alternative ASCE 7-10 Table 12.2-1 modified by Oregon Buildings Code Division Y Y scott.breneman@woodworks.org 48
Mass timber design Lateral framing systems Central core mass timber shearwalls Photo Credit: alex schreyer 103 CLT Diaphragms Strength of CLT rarely (never?) governs. Capacity provided by manufactures via ASTM standard testing. Standard to be included in PRG 320 Update. Strength of Connections covered by NDS 2015 and Proprietary Fastener Evaluation Reports scott.breneman@woodworks.org 49
CLT Floors as Diaphragms Panel In-Plane Strength: Panel strength generally does not govern diaphragm shear strength. Reference Design Values Not covered by APA PRG 320-12 product standard Are covered by New ICC AC455 Acceptance Criteria Ask for design values from the Manufacturers Connection Strength: Commodity connectors (e.g. Nails) per NDS 2015 Proprietary Connectors (Self-Tapping Screws) per Evaluation Reports, Manufacturer s Information and Engineering Mechanics. For seismic design, select connection details so ductile limit states govern capacities. SB26 CLT Diaphragm Design Example Paper scott.breneman@woodworks.org 50
SB27 CLT Diaphragm Design Example Paper Lateral load, w =1 kip/ft CLT Panels Shear Wall SB28 CLT Diaphragms Is the Diaphragm Rigid or Flexible?. scott.breneman@woodworks.org 51
CLT Diaphragms in US Seismic Applications Calculated Diaphragm Deflections OR Enveloped Diaphragm Design (check for both flexible and rigid diaphragm behavior) (check for conservatively flexible and conservatively stiff semi-rigid behavior) CLT Diaphragm Design Example Paper Detailed design example for simple diaphragm following NDS 2015, US CLT Handbook Includes approximate deflection equation: Modified 4-term wood panel sheathed diaphragm equation in SDWPS 15 # $%& = '()* +,-. + () +2)3 /0 ( 1 4 + 67 8 ( 9. Chord Flexure Panel Shear Connector Slip Chord Slip 2= : 9 : + : P L is panel length ; ) ; P W is panel width. is connector slip at diaphragm edge e n scott.breneman@woodworks.org 52
CLT Diaphragm Design Example Paper 0.283 in + 0.300 in + 0.568 in + 0.199 in = 1.35 in Seismic Detailing: An European Approach Fragiacomo, Vasallo et al. Yielding Connections Non Yielding Connections Designed to Overstrength factor of 1.3 to 1.6 of yielding connection strength Typical Assumption of Rigid Diaphragm Behavior for CLT wall and floor systems scott.breneman@woodworks.org 53
Seismic Detailing: US CLT Handbook Approach Yielding Connections NDS Yield Modes III and IV govern. Strength of other (non-yielding) limit states at connection designed to nominal yielding connection capacity. 1/ϕ = 1/0.65 = 1.54 overstrength factor Non Yielding Connections Chords and Anchorage Routes for Seismic Diaphragms Possible routes for near term seismic project designs under Alternative Means and Methods include: 1) Elastic Design Method Based on lower-bound strength of components Following new ASCE 7-16 alternative diaphragm method to determine elastic seismic diaphragm force demands 2) Capacity-Based Design Method Using designated yielding connections with overstrength design of non-desirable limit states. Based on yielding connection technologies of proven cyclic behavior! Relatively equivalent to Wood Structural Panel diaphragm behavior OR! Advanced Engineering with supporting testing to justify design scott.breneman@woodworks.org 54
SB6 WoodWorks Solutions Paper on CLT Modeling http://www.woodworks.org/wp-content/uploads/approach-to-clt-diaphragm-modeling-for-seismic-woodworks-jan-2017.pdf Additional Resources scott.breneman@woodworks.org 55
SB6 June 2016 Structures Magazine Article http://www.structuremag.org/wp-content/uploads/2016/05/c-strucdesign-breneman-jun161.pdf SB15 US CLT Handbook 1. Introduction 2. Manufacturing 3. Structural 4. Lateral 5. Connections 6. DOL and Creep 7. Vibration 8. Fire 9. Sound 10.Enclosure 11.Environmental 12.Lifting scott.breneman@woodworks.org 56
Source of CLT Handbook www.rethinkwood.com/masstimber Questions? This concludes The American Institute of Architects Continuing Education Systems Course Scott Breneman Scott.Breneman@WoodWorks.org 144 scott.breneman@woodworks.org 57
Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited. The Wood Products Council 2017 scott.breneman@woodworks.org 58