1996 LRFD Manual for Engineered Wood Construction

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viithickness (timbers), green shall be defined in accordancewith the provision of the applicable lumber grading rulescertified by the ALSC Board of Review.Horizontal diaphragm. A sheathed horizontal or nearlyhorizontal element (roof, floor) acting to transfer lateralforces to the vertical resisting elements.I-beams. Wood I-beams are custom designed and fabricatedfor specific applications. Lumber flanges and panelwebs are bonded with adhesives to form “I”, multiweb, orbox sections. The design of wood I-beams is in accordancewith App. A6 of this standard.I-joists (prefabricated). Structural members manufacturedusing sawn or structural composite lumber flangesand structural panel webs, bonded together with waterproofadhesives, forming an “I” cross-sectional shape. Thedesign of I-joists is in accordance with ASTM D5055-94.Joist (lumber). Pieces (nominal dimensions 2 to 4 in.(51 to 102 mm) in thickness by 5 in. (127mm) and widerwith rectangular cross-section graded primarily with respectto strength in bending when loaded on the narrowface. Typically used as framing members for floor or ceilings.Kiln dried. Lumber that has been seasoned in a chamberto a predetermined moisture content by applying heat.Laminated veneer lumber (LVL). A composite of woodveneer sheet elements with wood fibers primarily extendedalong the length of the member. Veneer thickness doesnot exceed 0.25 in. (6.4 mm).Limit state. A condition in which a structure or componentis judged either to be no longer useful for its intendedfunction (serviceability limit state) or to be unsafe (strengthlimit state).Load duration (time-effect). The period of continuousapplication of a given load, or the cumulative period ofintermittent applications of the maximum load.Load factor. A factor that accounts for unavoidable deviationsof the actual load from the nominal value and foruncertainties in the analysis that transforms the load intoa load effect.Load sharing. The load redistribution mechanism amongparallel components constrained to deflect together orjoined by crossing members such as sheathing or decking.Load/slip constant. The ratio of the applied load to aconnection and the resulting lateral deformation of the connectionin the direction of the applied load.LRFD (Load and Resistance Factor Design). A methodof proportioning structural components (members, connectors,connecting elements, and assemblages) using loadand resistance factors such that no applicable limit stateis reached when the structure is subjected to all appropriateload combinations.Lumber. The product of the sawmill and planing millusually not further manufactured other than by sawing,resawing, passing lengthwise through a standard planingmachine, cross-cutting to length, and matching.Lumber Sizes. Lumber is typically referred to by sizeclassifications. Two of the frequently used size classificationsare dimension and timbers. Additionally, lumberis specified by manufacturing classification. Rough lumberand dressed lumber are two of the routinely usedmanufacturing classifications.Boards. Lumber of less than nominal 2 in. (51 mm) thicknessand of nominal 2 in. (51 mm) or greater width.Dimension. Lumber from nominal 2 in. through 4 in. (51mm through 102 mm) thick and nominal 2 or more in. (51or more mm) wide.Dressed size. The dimensions of lumber after surfacingwith a planing machine. Usually 1/2 to 3/4 in. (12.7 to19.0 mm) less than nominal size. The American SoftwoodLumber Standard lists standard dressed sizes.Rough lumber. Lumber that has not been dressed (surfaced)but that has been sawed, edged, and trimmed atleast to the extent of showing saw or other primary manufacturingmarks in the wood on the four longitudinalsurfaces of each piece for its overall length. Lumber surfacedon one edge (S1E), two edges (S2E), one side (S1S),or two sides (S2S) is classified as rough lumber in theunsurfaced width or thickness.Timbers. Lumber of nominal 5 in. (127 mm) or greaterin least dimension.Stress-graded lumber. Lumber graded for its mechanicalproperties.AMERICAN FOREST & PAPER ASSOCIATION
viiiMachine evaluated lumber (MEL). Lumber that hasbeen nondestructively evaluated by mechanical gradingequipment. Each piece is evaluated and marked to indicateits strength classification. MEL lumber is alsorequired to meet certain visual requirements.Machine stress-rated (MSR) lumber. Lumber that hasbeen evaluated by mechanical stress-rating equipment.Each piece is nondestructively tested and grademarked toindicate the assigned bending strength and modulus ofelasticity. MSR lumber is also required to meet certainvisual requirements.Main member. In three-member connections, the centermember. In two-member connections, the thicker member.Mat-formed panel. A structural-use panel designationrepresenting panels manufactured in a matformed process,such as oriented strand board and wafer board.Moisture content. The weight of the water in wood expressedas a percentage of the weight of the wood fromwhich all water has been removed (ovendry).Nominal loads. The loads specified by the applicablecode.Nominal size. The approximate commercial size by whichlumber products are known and sold in the market. Thenominal size is generally greater than the actual dimensions,i.e., a dry 2 x 4 is surfaced to 1½ in. by 3½ in. (38mm by 89 mm).Oriented strandboard. A mat-formed structural-usepanel comprised of thin rectangular wood strands arrangedin cross-aligned layers with surface layers normally arrangedin the long panel direction and bonded withwaterproof adhesive.Ovendry wood. Wood dried until it is free of any moisture.Panel. A sheet-type wood product.Panel rigidity. Shear rigidity of a panel, the product ofpanel thickness and modulus of rigidity.Panel shear. Shear developed in a structural-use paneldue to in-plane loads, commonly called “shear throughthe thickness and is developed in shear walls, diaphragms,and webs of I-joists.Panel stiffness. Flexural or axial stiffness of a panel.The product of panel section property and modulus of elasticity.Parallel strand lumber (PSL). A composite of woodstrandelements with wood fibers primarily oriented alongthe length of the member. The least dimension of thestrands is not greater than 0.25 in. (6.4 mm) and the averagelength is not less than 150 times the least dimension.Performance rating. A classification designating enduseapplications for which specific performance testprocedures and criteria have been established.Performance standard. A standard for trademarkedproducts based on performance. Performance is measuredby tests that approximate end-use conditions.Pile. Round timber structural element of any size or length,that is driven or otherwise introduced into the soil for thepurpose of providing vertical or lateral support.Pitch or spacing. The longitudinal center-to-center distancebetween any two consecutive holes or fasteners in arow.Planar shear. The shear developed in structural-use panelsdue to flatwise bending, commonly referred to as“rolling shear” in plywood.Plank. A piece of lumber, from 2 to 4 in. (51 to 102 mm)thick, used with the wide face placed horizontally (differsfrom joist only that latter is used on edge).Ply. A single sheet of veneer, or several strips laid withadjoining edges that form one veneer lamina in a gluedplywood panel.Plywood. A structural-use panel comprised of plies ofwood veneer arranged in cross-aligned layers. The pliesare bonded with an adhesive that cures on application ofheat and pressure.Pole. A round timber of any size or length, usually usedwith the larger end in the ground.Pole construction. A form of construction in which theprincipal vertical members are round poles or sawn timbers(post-frame construction) embedded in the groundand extending vertically above ground to provide bothfoundation and vertical framing for the structure.AMERICAN WOOD COUNCIL
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1996 LRFD Manual for Engineered Wood Construction

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