Presentation on theme: "Wood Structural Panels"— Presentation transcript:
1Wood Structural Panels CE A433 – Spring 2008T. Bart Quimby, P.E., Ph.D.University of Alaska AnchorageCivil Engineering
2Wood Structural Panel Uses Structural panels are used for a wide variety of uses includingSheathing of roofs, floors, and walls toTransfer pressure loads normal to the surface to supporting framingCarry shear loads in structural diaphragmsStructural Components such asLumber-plywood beamsVarious types of panel componentsGusset PlatesConcrete Formwork
3Sheathing Applications See figure 8.1 from textThe required panel thickness is a function of the loads applied normal to the surfaceAttachment of sheathing is a function of the loads in the plane of the panel (i.e. diaphragm shears)
4Types of Wood PanelsThe principle types of wood panels used in timber construction include:PlywoodOriented Strand Board (OSB)WaferboardComposite panelsStructural particle board
5Plywood Made by gluing veneers together Plys have different names FaceBackCrossbandCenterGrain direction is alternated by layerThis creates different strengths in each principle directionVeneers come in different qualitiesDependant on number and types of imperfections
6Section Properties by Principle Direction See text figure 8.6Face Grain
7More PlywoodPlywood comes in many different thickness and plys.
8Species Groups Species are grouped together by similar strengths. See text for the five plywood species groups.
9Veneer GradesVeneers come in different levels of quality, based on imperfections.See text for different grade specifications.
10Exposure Durability Classifications U.S. Product Standard PS-1 – Construction and Industrial Plywood SpecificationInteriorExteriorAPA Performance-rated panelsExposure 1: Interior plywood with exterior glueExposure 2: Interior panels
11Plywood Grades There are a large number of grades Most SHEATHING applications useC-C ExteriorC-D Exterior 1C-C STR IC-D STR 1The “STR I” grades have added strength properties and are more expensive.Span ratings give the maximum recommended span lengths for roof and subfloor applicationsAssumes strong direction over two or more spansMust satisfy edge support requirementsDifferent thickness can result in same span rating
12Plywood Grade StampsSee examples in the text (pgs 8.15, 8.18, 8.19, 8.29)Also see…
14Oriented Strand BoardMade of wood strands or wafers directionally oriented, compressed and bonded by a resin.Two different surfacesGrade designated by Performance-based ratings and PS 2
15Combined Sheathing-Siding T1-11 is commonly used.See text figures
16Two Layer Floor Sheathing Two Layer SystemSee text Figure 8.28SubfloorThe structural support for the floorUnderlaymentProvides a smooth surface for floorNon StructuralNeed to make sure the panel edges don’t align with adjacent layer.Second number is span rating when used as subfloor
18One Layer Floor Sheathing Must have some means of connecting edges of panels so that they move togetherTongue & GrooveBlockingOffset underlaymentLightweight concreteThick wood finished flooring
19Selection of Floor Sheathing “typical wood structural panel applications for floor sheathing are not controlled by uniform load criteria, but instead are based on deflection under concentrated loads and how the floor feels to building occupants.” (text pg 8.27)Can use span ratings to select the flooringSee “Guide to Panel Use” (ASD/LRFD Manual for Engineered Wood Construction, Table M9.1-1), and Table M9.2-1 for usage and typical span ratings.
20Wall Sheathing All edges must be blocked See text Figure 8.16 Architectural panels can be used that are combined sheathing and sidingDetails for preventing water infiltration are shown in text figure 8.19c
21Structural Calculations Not normally done for sheathing applicationsUse span ratings.The ASD/LRFD Design Manual for Engineered Wood ConstructionAPA Documents:Load-Span Tables for APA Structural Use PanelsPanel Design Specification