Permanent Bracing Commentary - Cover - Concord …

1 Commentary for Permanent Bracingof Metal Plate Connected Wood TrussesJohn E. Meeks, , Original AuthorReviewed by theEngineering Review Committeeof the Wood Truss Council of Americaand theTechnical Advisory Committeeof the Truss Plate InstituteWood Truss Council of AmericaOne WTCA Center6425 Normandy Lane Madison, WI 53719-1133608/274-4849 608/274-3329 (fax) 1999 Wood Truss Council of AmericaCOMMENTARY FOR Permanent Bracing OF METAL PLATE CONNECTED WOOD TRUSSESTABLE OF 2 GENERAL 2 Roof or Floor Loads .. 3 Architect and/or Engineer of Record - Building Designer .. 3 Approval of Truss Submittals .. 5 Truss Installation .. 5 TRUSS 6 Permanent Bracing per ANSI/TPI 1 .. 6 Web Member Plane .. 6 Truss Members in Compression .. 6 Truss Members in Tension .. 7 Special 7 TRUSS SYSTEM 7 Lateral Stability Bracing .. 7 SPECIAL 8 Gable End Braces .. 8 Diagonal Braces .. 9 Sway Bracing .. 10 Top Chord Bracing - Multi-piece Truss.

2 12 Chord Extensions and Fillers .. 13 Valley Framing Bracing .. 16 Hip Truss Bracing .. 17 Mono Pitch Triangular Trusses .. 18 Top Chord Bracing by Purlins .. 19 Knee Braces .. 21 Bottom Chord Bracing .. 21 Floor Trusses .. 23 ILLUSTRATIVE 26iTRUSS TECHNOLOGY TODAYiiCOMMENTARY FOR Permanent Bracing OF METAL PLATE CONNECTED WOOD TRUSSESINTRODUCTIONB uilding Designers and Contractors recognize the design versatility and economies of MetalPlate Connected Wood Trusses (MPCWT). From its beginning in the early 1950 s, the use ofMPCWT has increased to the point of being the dominant roof framing method in the residentialmarket and continues penetration into commercial, institutional, and agricultural markets. Animportant contribution to the growth of the use of trusses has been the early use of computeranalysis, material optimization and the design efficiencies of wood trusses by the truss are offered to the marketplace as individual engineered wood components to beincorporated into a complete structural system by the Building Commentary is intended to give guidelines to the Building Designer in defining those partsof the structure that, under present industry practice, will be designed by the Truss Designer andthose parts that will be designed by the Building Designer.

3 The Building Designer must deter-mine and use the proper design criteria when applying the information provided within : The registered architect responsible for all or part of the design of the BuildingStructural System and/or who produces structural drawings which are included in the BuildingStructural System Design Structural System: The completed combination of structural elements, connectionsand systems, which serve to support the Building s self weight, and all applicable live andenvironmental Designer: The individual or organization responsible for the overall design of theBuilding Structural System in accordance with all Legal Requirements, and with respect tocompliance of applicable state architectural and engineering registration laws. The BuildingDesigner may be an Architect, the Engineer of Record, a registered building designer, the owneror the Structural System Design Documents: The architectural drawings, structural drawings,and any other drawings, specifications, and addenda which set forth the overall structural designof the Building Structural System and which are issued by the Building Designer.

4 These documentsshould contain complete detailed information on the wood truss structural system, includingframing plan, section details, truss profiles or configurations, connections, tie-downs, andpermanent Bracing requirements, for contractor and supplier bidding : The individual or organization responsible for constructing the building inaccordance with all Legal Requirements, the Building Structural System Design Documentsand the Truss Submittals. The term Contractor shall include those subcontractors who have adirect contract with the Contractor to perform all or a portion of the storage, handling, andinstallation of the of Record: The registered engineer responsible for the design of the Building StructuralSystem and/or who may produce structural drawings included in the Building Structural SystemDesign Documents. The Engineer of Record is one who is legally eligible to seal the structuraldrawings contained within the Building Structural System Design Documents.

5 This sealacknowledges that he/she has performed or supervised the analysis, design, and documentpreparation of the Building s Structural System, and has knowledge of the requirements for theload carrying Building Structural TECHNOLOGY TODAYL egal Requirements: The applicable provisions of all statutes, laws, rules, regulations,ordinances, codes or orders of any governmental authority of the United States of America, anystate, and any political subdivision or quasi-governmental authority of any of the same, includingbut not limited to departments, commissions, boards, bureaus, agencies, counties, municipalities,provinces, and other : An individual metal plate connected wood structural element manufactured by the TrussManufacturer and supplied to the Designer: The individual or organization responsible for the design of metal plate connectedwood trusses, and with respect to compliance of applicable state architectural and engineeringregistration laws.

6 The Truss Designer may be a registered engineer and accordingly may bereferred to as a Truss Design Engineer or design Design Drawing: The graphic depiction of an individual Truss prepared by the Manufacturer: An individual or organization regularly engaged in the manufacturing Placement Plan: The drawing identifying the location assumed for each Truss based onthe Truss Manufacturer s interpretation of the Building Structural System Design Truss Placement Plan will reflect a truss identifying mark and perhaps other products andstructural elements supplied by the Truss Manufacturer so that they may be more easily identifiedby the Contractor during field Submittals: Those Truss Design Drawings and the Truss Placement Plan, if required bythe contract, submitted to the owner, Building Designer and Contractor for their review purpose of this document is to provide guidelines for Building Designers to use in designingand specifying the Permanent Bracing for metal plate connected wood truss systems.

7 The emphasisfor Bracing wood trusses is always on the application of triangulation, perpendicular to the planeof the trusses, which will hold every truss component in its proper position to create a structurallystable roof or floor truss document is written in general terms only and does not include specific Bracing memberand connection design. Lateral forces due to wind or seismic loads must be considered separatelyby the Building Designer. This document is not intended to take the place of any building is up to the Building Designer to decide how the Building Structural System will function andhow the wood truss components will be incorporated within this PROCEDUREB efore trusses can be analyzed, certain basic design considerations must be decided. Usually,the character of the floor/roof covering, the truss span, and the geometrical shape (profile) of thetrusses are fixed by architectural requirements. The span and spacing of trusses are also usuallyestablished by the architectural location, in plan, of the supporting columns, beams, girders,and/or load bearing walls.

8 The location of the building site and its exposure will fix the amount2 Commentary FOR Permanent Bracing OF METAL PLATE CONNECTED WOOD TRUSSESof snow and wind loads or seismic loading which must be considered in the overall design of theBuilding Structural System. Design loads are usually based upon local building code requirementsor ANSI/ASCE 7-95, Minimum Design Loads for Buildings and Other Structures (1).Roof or Floor Loads: The loads which must be considered by the Building Designer in thedesign of a roof or floor truss system usually consist of, but are not limited to the following:a. The weight of the deck materials and coverings, including the anticipation of future layers ofcoverings, such as replacing existing floor or roofing material with heavier floor or The weights of purlins, Bracing and other The weight of the truss Ceiling loads, Special loads, such as suspended loads, concentrated loads, sprinkler piping, HVAC or othermechanical Maximum expected roof and floor live loads, including anticipated live load changes due topotential changes in Maximum and minimum expected snow loads, including Maximum expected wind loads, including distinct zone loadings, and any transfer loadingsrequired by the structural wind analysis, where Maximum expected seismic loads, and any transfer loadings required by the structural seismicanalysis, where and/or Engineer of Record - Building Designer.

9 Metal plate connected wood trussesare required by all major model building codes to be designed and manufactured in accordancewith ANSI/TPI 1, National Design Standard for Metal Plate Connected Wood Truss Construction(2), a national consensus standard published by the Truss Plate Institute (TPI) and approved bythe American National Standards Institute (ANSI). Section of ANSI/TPI 1-1995 providesthe definition of Building Designer that is virtually identical to the one included at the beginningof this document (Note: The definitions set forth in this Commentary have been submitted foradoption into ANSI/TPI 1-2000). In addition, ANSI/TPI 1 also The Building Designer shall make provisions for bearings, cross and lateral Bracing , Bracing to transfer truss member buckling forces to the structure, and Bracing to resist wind,seismic or other horizontal Connections between two or more [wood] members, all of which are designed or specifiedby the Truss Designer, shall be designed or specified by the Truss Designer.

10 Connections betweentwo or more [wood] members, one or more of which are not designed or specified by the TrussDesigner, shall be designed or specified by the Building Designer. See Figure 1 on page The Building Designer shall specify the following:a. Design loads as described Truss profile [shape] and intended support Temperature and moisture environment for the intended Any special requirements to be considered in the truss TECHNOLOGY ..the Building Designer shall provide for the following in the design and detailing of thebuilding:a. Truss Truss movement due to moisture and temperature Truss supports and anchorage accommodating horizontal, vertical or other reactions Permanent truss Bracing to resist wind, seismic and any other lateral forces acting perpendicularto the plane of the Permanent lateral Bracing as specified by the Truss Designer, to prevent buckling of individualtruss members due to design Building Designer is legally responsible for the overall design of the Building StructuralSystem.