The Long and Short of Wood Roof Systems
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9/30/2014 The Long and Short of Wood Roof Systems Presented by Scott Breneman, PhD, PE, SE October 1, 2014 Photo Al Karevy/Bensonwood “The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program 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 program 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. 1 9/30/2014 Course Description This course is an overview of the many framing systems commonly used in buildings in the United States for a variety of span lengths. The presentation will review the possible wood structural framing systems including rafters, metal plated wood trusses, engineered wood products and hybrid roof systems. Also covered will be how these components can be combined to create efficient and versatile roof framing systems. All of these concepts will be reinforced through the presentation of real example projects with details on the framing system used to achieve the project goals. Learning Objectives At the end of this program: • Participants will be familiar with wood framing options available for use as roof framing and be able to evaluate different framing systems to use for building projects • Participants will be familiar with the variety of roof geometries that are possible with wood framing systems • Through the presentation of several project case studies, the participant will understand how long span roof systems can be built from all wood and hybrid wood structural configurations • Participants will be familiar with the International Building Code provisions that allow the use of wood systems in many roof applications including use in non-combustible Type I and Type II construction buildings 2 9/30/2014 Wood Roof Riding Arena 3 9/30/2014 Commercial Strip Mall Christ the King Catholic Church Christ the King Catholic Church Hamilton, GA Architect: CDH Partners, Inc. Engineer: KSI Structural Engineers Timber trusses and wood decking Spire created unique skylight effect 4 9/30/2014 Photo courtesy RedBuilt Photo Scott Breneman - WoodWorks Freedom Truck Center, Spokane, WA Architects: ALSC Architects Structural Engineer: DCI Engineers University Laval Soccer Stadium, Quebec City Architect: ABCP Architecture + urbanisme Photos courtesy Nordic Engineered Wood Products 5 9/30/2014 Layton Petro Mart, Greenfield, Wisconsin ARCHITECT: Arquitectura, Inc. ENGINEER: Jendusa Engineering Associates, Inc. PHOTOS: Arquitectura, Inc. Outline of Presentation • Wood Roof Components • Wood Roof Systems • IBC Code Provisions for Wood Roofs • Why Consider Wood 6 9/30/2014 Outline of Presentation • Wood Roof Components • Wood Roof Systems • IBC Code Provisions for Wood Roofs • Why Consider Wood Components of Roof System? 7 9/30/2014 Components of a Wood Roof System Components of a Wood Roof System Continuous Weather Proof Layers 8 9/30/2014 Components of a Wood Roof System Structural Sheathing Components of a Wood Roof System Structural Framing 9 9/30/2014 Wood Roof Sheathing Options Wood Structural Panels Oriented Strand Board (OSB) and Plywood Solid Sawn Decking 2x, 3x and 4x dimensional lumber Mechanically Laminated or Tongue & Groove Panel Products: Structural Insulated Panels (SIPS) Cross-Laminated Timber (CLT) Panels Wood Structural Panels Plywood - the original engineered wood panel (>100 years) Oriented Strand Board (OSB) - a second generation engineered wood panel (>25 years) 10 9/30/2014 IBC 2012 2303.1.4 Wood structural panels. Wood structural panels, when used structurally (including those used for siding, roof and wall sheathing, subflooring, diaphragms and built-up members), shall conform to the requirements for their type in DOC PS 1, DOC PS 2 or ANSI/APA PRP 210. Each panel or member shall be identified for grade, bond classification, and Performance Category by the trademarks of an approved testing and grading agency. The Performance Category value shall be used as the “nominal panel thickness” or “panel thickness” whenever referenced in this code. Wood structural panel components shall be designed and fabricated in accordance with the applicable standards listed in Section 2306.1 and identified by the trademarks of an approved testing and inspection agency indicating conformance to the applicable standard. In addition, wood structural panels when permanently exposed in outdoor applications shall be of Exterior type, except that wood structural panel roof sheathing exposed to the outdoors on the underside is permitted to be Exposure 1 type. APA Engineered Wood Construction Guide 11 9/30/2014 Lumber Decking • See IBC 2012 2304.8 • American Wood Council’s Wood Construction Data No. 2 “Tongue and Grove Roof Decking” Lumber Decking Code Acceptance for 2, 3 and 4 inch thick Tongue & Groove Lumber Decking per IBC 2012 2304.8 3x6 Double T&G Pine 2x6 T&C Doug Fir Photo Bear Creek Lumber Photo Southern Wood Specialities 12 9/30/2014 Lumber Decking Layup Options Details in IBC with further information in AWC WCD 2 American Wood Council Wood Construction Data 2 Tongue and Groove Roof Decking Christ the King Catholic Church Christ the King Catholic Church Hamilton, GA Architect: CDH Partners, Inc. Engineer: KSI Structural Engineers Timber trusses and wood decking Spire created unique skylight effect 13 9/30/2014 Lumber Roof Decking Spans • AWC WCD 2 T&G Decking Design Tools. • Used with Lumber Design Values from National Design Specification for Wood Construction and Supplement. Lumber Roof Decking Spans • 2 inch can span up to 8 feet or more • 3 inch can span up to 12 feet or more • 4 inch can span up to 16 feet or more • Spans depend on Loads, Species and Grade of Lumber, Deck Layup Pattern, Acceptable Deflection, etc. 14 9/30/2014 Diaphragm Sheathing Limitations • IBC 2012 2306.2 applies to wood-framed diaphragms and references AWC Special Design Provisions for Wind & Seismic 2008 (SDPWS): • Example capacities are: Diaphragm MaX Aspect MaX Possible Allowable Shear Type Ratio Capacity (ASD) in SPDWS Lumber Sheathing Horizontal 2x sheathing 2:1 VW=70 plf, VS=50 plf 1 layer Diagonal 2x sheathing 3:1 VW=420 plf, VS=300 plf 2 layers Diagonal 2x sheathing 4:1 VW=840 plf, VS=600 plf Wood Panels Blocked WSP* 4:1 VW=2520 plf, VS=1800 plf Unblocked WSP 3:1 VW=447 plf, VS=320 plf *Maximum value from high load diaphragms Components of a Wood Roof System Structural Framing Rafters 15 9/30/2014 Components of a Wood Roof System Structural Framing Purlins Components of a Wood Roof System Structural Framing Rafters and Purlins 16 9/30/2014 Ithaca Foreign Car Repair, Ithaca NY Photos courtesy New Energy Works Timberframers Ithaca Foreign Car Ithaca Foreign Car Repair Photos courtesy New Energy Works Timberframers 17 9/30/2014 Solid Sawn Roof Framing Design Routes: IBC 2012 2308 – Conventional Light-Frame Construction AWC NDS 2012 – Engineered Design AWC Wood Frame Construction Manual 2012 -Design tools based upon NDS Solid Sawn Roof Framing Spans Possible long spans based upon a common 24” o.c. spacing in lightly loaded applications Size Achievable Span 2x4 8 ft 2x6 12 ft 2x8 16 ft 2x10 20 ft 2x12 24 ft Acceptable spans depend on Loads, Species and Grade of Lumber, Acceptable Deflection, etc. See NDS 2012 or Wood Frame Construction Manual 2012 for design 18 9/30/2014 Glulam Glulam What is Glulam? Glulam = a structural composite of lumber and adhesives 19 9/30/2014 Dispersal of Strength Reducing Characteristics Single Lamination Glued Laminated Timber Spans of 100 feet or greater achievable 12-1/4” X 84” 140 ft. clear span Camber = 8” 20 9/30/2014 FleXibility of Shapes and Spans Portland International Jetport, Portland, Maine Architect : Gensler Structural Engineer: Oest Associates Timber Engineer: DeStefano & Chamberlain Photos courtesy DeStafano & Chamberlain, Inc. 21 9/30/2014 Portland International Jetport, Portland, Maine Architect : Gensler Structural Engineer: Oest Associates Timber Engineer: DeStefano & Chamberlain Photos courtesy DeStafano & Chamberlain, Inc. Portland International Jetport, Portland, Maine 32 by 64 feet bays Photos courtesy DeStafano & Chamberlain, Inc. 40,000 sf timber roof 22 9/30/2014 Lemay America Auto Museum 104’ Span Glulam Arches Photos courtesy Western Wood Structures Glulam purlins @ 4’ o.c Promega Feynman Center, The Crossroads, Madison, Wisconsin ARCHITECT: Uihlein-Wilson Architects, Inc. ENGINEER: EwingCole DESIGN CONSULTANT: Archemy Consulting PHOTOS: Aitor Sanchez/EwingCole 23 9/30/2014 Promega Feynman Center, The Crossroads, Madison, Wisconsin Photos: Aitor Sanchez/EwingCole Pre Fabricated Wood I-Joists Recognized in IBC 2303.1.2 using ASTM D 5055 Proprietary Products with Evaluation Reports SCL or lumber flanges Structural Structural glue joints wood panel web 24 9/30/2014 Prefabricated Wood I-Joists Wide range of depths and flange widths Commercial Strip Mall 25 9/30/2014 Havens Elementary School, Piedmont CA Design : ATI Architects and Engineers General Contractor: Webcor 46,000 sf school replacement Completed 2010 Photo Janelle Leafblad - WoodWorks Havens Elementary School, Piedmont CA Design : ATI