DESIGN OF LOADBEARING TALL WOOD STUDS FOR WIND AND GRAVITY LOADS (DES30) John Buddy Showalter, P.E. Vice President, Technology Transfer American Wood Council Lori Koch, P.E. Manager, Educational Outreach American Wood Council Description Proper design of wood structures to resist high wind loads requires the correct use of wind load provisions and member design properties. A thorough understanding of the interaction between wind loads and material properties is important in the design process. Adjustments from reference wind conditions to extreme-value peak gusts require designers to make similar adjustments to design properties to ensure equivalent and economic designs. Wind load provisions have been developed for design of major structural elements using Main Wind-Force Resisting System (MWFRS) loads and secondary cladding elements using Component & Cladding (C&C) loads. Elements and subassemblies which receive loads both directly and as part of the main wind force resisting system, such as wall studs, must be checked independently for MWFRS loads and C&C loads. A load bearing stud wall design example based on the allowable stress design methods outlined in AWC's 015 National Design Specification (NDS ) for Wood Construction and 015 Wood Frame Construction Manual along with ASCE 7-10 Minimum Design Loads for Buildings and Other Structures will demonstrate standard design checks for limit states of strength and deflection. Learning Objectives Upon completion of this webinar, participants will: 1. Understand how to analyze wall framing as part of the MWFRS per ASCE 7-10. Understand why wall framing is analyzed using out of plane C&C wind pressures independent of gravity loads 3. Be familiar with various ASCE 7-10 ASD load combinations used for bearing walls 4. Be knowledgeable of standards including the 015 NDS, 015 WFCM, and ASCE 7-10 used for design of tall walls 1
This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of AWC is prohibited. American Wood Council 017 The American Wood Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider # 5011137. 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. 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 Questions related to specific materials, methods, and request. services will be addressed at the conclusion of this presentation.
Poll Question What is your profession? a) Architect/Building Designer b) Engineer c) Code Official d) Builder e) Other 3
Course Outline Background on Design Loads Wind and Gravity Engineered Provisions Calculating Design Loads Prescriptive Provisions Wood Frame Solutions Design Example Reference Material 4
Reference Codes and Standards 001 WFCM 01 WFCM 015 WFCM ASCE 7-10 003, 006, 009 IRC/IBC 01 IRC/IBC 015 IRC/IBC 015 WFCM 5
By downloading this file to your computer, you are accepting and agreeing to the terms of AWC s end-user license agreement (EULA), which may be viewed here: End User License Agreement. Copyright infringement is a violation of federal law subject to criminal and civil penalties. WFCM Wood Frame Construction Manual for One- and Two-Family Dwellings COMMENTARY 015 EDITION 6
GENERAL INFORMATION WFCM Commentary C1.1 Scope C1.1.1 General The scope statement limits applicability of the provisions of the Wood Frame Construction Manual to one- and two-family dwellings. This limitation is related primarily to assumed design loads and to structural configurations. Code prescribed floor design loads for dwellings generally fall into the range of 30 to 40 psf, with few additional requirements such as concentrated load provisions. In these applications, use of closely spaced framing members covered by structural sheathing has proven to provide a reliable structural system. C1.1. Design Loads Unless stated otherwise, all calculations are based on standard linear elastic analysis and Allowable Stress Design (ASD) load combinations using loads from ASCE 7-10 Minimum Design Loads for Buildings and Other Structures. Dead Loads Unless stated otherwise, tabulated values assume the following dead loads: Roof Ceiling Floor Walls Partitions 10 psf 5 psf 10 psf 1 psf (for Seismic) 11 psf 8 psf (for Seismic) ASD wind pressures, pmax, for Main Wind-Force Resisting Systems (MWFRS) and Components and Cladding (C&C) are computed by the following equations, taken from ASCE 7-10: MWFRS Envelope Procedure: pmax = q[(gcpf) (GCpi )] (lbs/ft) q = 0.60 qh qh = 0.0056KzKztKdV Unless stated otherwise, tabulated values assume the following live loads: Wind Loads Basic Design Equations: where: Live Loads Roof Floor (sleeping areas) Floor (living areas) no significant structural discontinuities. In addition, the buildings are assumed to be enclosed structures in which the structural elements are protected from the weather. Partially enclosed structures are subjected to loads that require further consideration. For wind load calculations, ASCE 7-10 is used. ASCE 7-10 calculations are based on 700-year return period three second gust wind speeds corresponding to an approximate 7% probability of exceedence in 50 years, and use combined gust and pressure coefficients to translate these wind speeds into peak design pressures on the structure. The 015 WFCM includes design information for buildings located in regions with 700-year return period three second gust design wind speeds between 110 and 195 mph. 0 psf 30 psf 40 psf (ASCE 7-10 Equation 8.3-1) GCpf = external pressure coefficients (ASCE 7-10 Figure 8.4-1) GCpi = internal pressure coefficients (ASCE 7-10 Table 6.11-1) C&C: Wind forces are calculated assuming a box-like structure with wind loads acting perpendicular to wall and roof surfaces. Lateral loads flow into roof and floor diaphragms and are transferred to the foundation via shear walls. Roof uplift forces are transferred to the foundation by direct tension through the wall framing and tension straps or wall sheathing. Shear wall overturning forces are resisted by the structure s dead load and by supplemental hold down connections. Implicit in the assumption of a box-like structure is a roughly rectangular shape, relatively uniform distribution of shear resistance throughout the structure, and where: pmax = q[(gcp) (GCpi)] (lbs/ft) q = 0.60qh qh = 0.0056KzKztKdV (ASCE 7-10 Equation 30.3-1) GCp = external pressure coefficients (ASCE7-10 Figures 30.4-1,30.4-A, B, &C) GCpi = internal pressure coefficients (ASCE 7-10 Table 6.11-1) The calculation of ASD velocity pressure, q, for various wind speeds and Exposures is shown in Table C1.1. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 7
COMMENTARY TO THE WOOD FRAME CONSTRUCTION MANUAL WFCM Commentary Table C1.1 ASD Velocity Pressure, q (psf), for Exposures B, C, and D and 33' MRH Exposure B Exposure C Exposure D 110 11.37 15.80 18.64 115 1.43 17.7 0.37 ASD Velocity Pressure, q (psf) 700-yr. Wind Speed 3-second gust (mph) 10 130 140 150 160 170 13.54 15.89 18.4 1.15 4.06 7.17 18.80.06 5.59 9.38 33.4 37.73.18 6.04 30.0 34.66 39.44 44.5 180 30.46 4.30 49.9 GENERAL INFORMATION Exposure Category 1 195 35.74 49.65 58.58 q = 0.6 qh and qh = 0.0056 Kz Kzt Kd V Kz (33 ft) = 0.7 ASCE 7-10 Table 8.3-1 (MWFRS), Table 30.3-1(C&C) at mean roof height (MRH) of 33 ft Kzt = 1.0 No topographic effects Kd = 0.85 ASCE 7-10 Table 6.6-1 Design wind pressures in ASCE 7-10 are based on an ultimate 700-year return period. Since the WFCM uses allowable stress design, forces calculated from design wind pressures are multiplied by 0.60 in accordance with load combination factors per ASCE 7-10. For example, the ASD velocity pressure, q, at 150 mph for Exposure B is calculated as follows: q = 0.6 (0.0056)(0.7)(1.0)(0.85)(150) (lbs/ft) = 1.15 (lbs/ft) Uplift Calculations Note that the worst case of internal pressurization is used in design. Internal pressure and internal suction for MWFRS are outlined in WFCM Tables C1.3A and C1.3B, respectively. Pressure coefficients and loads for wind parallel and perpendicular to ridge are tabulated. Parallel to ridge coefficients are used to calculate wind loads acting perpendicular to end walls. Perpendicular-toridge coefficients are used to calculate wind loads acting perpendicular to side walls. Pressures resulting in shear, uplift, and overturning forces are applied to the building as follows: Shear Calculations intermediate floor diaphragms (one-half from above and one-half from below) and one-half of the bottom story goes directly into the foundation. Lateral roof and wall pressures for determining diaphragm and shear wall loads are calculated using enveloped MWFRS coefficients. Spatially-averaged C&C coefficients are used for determining lateral framing loads, suction pressures on wall and roof sheathing, and exterior stud capacities. The horizontal component of roof pressures is applied as a lateral load at the highest ceiling level (top of the uppermost wall). Windward and leeward wall pressures are summed and applied (on a tributary area basis) as lateral loads at each horizontal diaphragm. For example, in typical two story construction, one-half of the height of the top wall goes to the roof or ceiling level, a full story height goes to Uplift for roof cladding is calculated using C&C loads. Uplift connections for roof framing members are calculated using enveloped MWFRS loads. The rationale for using MWFRS loads for computing the uplift of roof assemblies recognizes that the spatial and temporal pressure fluctuations that cause the higher coefficients for components and cladding are effectively averaged by wind effects on different roof surfaces. The uplift load minus sixty percent of the roof and/or ceiling dead load is applied at the top of the uppermost wall. As this load is carried down the wall, the wall dead load is included in the analysis. The dead load from floors framing into walls is not included, in order to eliminate the need for special framing details where floors do not directly frame into walls. Overturning Calculations Overturning of the structure as a result of lateral loads is resisted at the ends of shear walls in accordance with general engineering practice, typically with hold downs or other framing anchorage systems. In the WFCM, overturning loads are differentiated from uplift loads. Overturning moments result from lateral loads which are resisted by Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 8
GENERAL INFORMATION WFCM Commentary shear walls. Uplift forces arise solely from uplift on the roof, and are transferred directly into the walls supporting the roof framing. ASCE 7-10 requires checking the MWFRS with a minimum 5 psf ASD lateral load on the vertical projected area of the roof and a 10 psf ASD lateral load on the wall. The 015 WFCM incorporates this design check. Snow Loads The 015 WFCM includes design information for snow loads in accordance with ASCE 7-10 for buildings located in regions with ground snow loads between 0 and 70 psf. Both balanced and unbalanced snow load conditions are considered in design. Seismic Loads The 015 WFCM includes seismic design information in accordance with ASCE 7-10 for buildings located in Seismic Design Categories A-D, as defined by the 015 IRC. b. Building Length and Width Limiting the maximum building length and width to 80 feet is provided as a reasonable upper limit for purposes of tabulating requirements in the WFCM. C1.1.3. Floor, Wall, and Roof Systems See C.1.3. (Floor Systems), C.1.3.3 (Wall Systems), and C.1.3.4 (Roof Systems). C1.1.4 Foundation Provisions Design of foundations and foundation systems is outside the scope of this document. C1.1.5 Protection of Openings Design for sliding snow is outside the scope of this document. Wind pressure calculations in the WFCM assume that buildings are fully enclosed and that the building envelope is not breached. Interior pressure coefficients, GCpi, of +/-0.18 are used in the calculations per ASCE 7-10 Table 6.11-1. Penetration of openings (e.g. windows and doors) due to flying debris can occur in sites subject to high winds with a significant debris field. Where these areas occur, opening protection or special glazing requirements may be required by the local authority to ensure that the building envelope is maintained. C1.1.3 Applicability C1.1.6 Ancillary Structures C1.1.3.1 Building Dimensions Design of ancillary structures is outside the scope of this document. C1.1..1 Torsion Design for torsion is outside the scope of this document. C1.1.. Sliding Snow a. Mean Roof Height Building height restrictions limit the wind forces on the structure, and also provide assurance that the structure remains low-rise in the context of wind and seismic-related code requirements. The tables in the WFCM are based on wind calculations assuming a 33 ft mean roof height, (MRH). This assumption permits table coverage up to a typical 3-story building. Footnotes have been provided to adjust tabulated requirements to lesser mean roof heights. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 9
By downloading this file to your computer, you are accepting and agreeing to the terms of AWC s end-user license agreement (EULA), which may be viewed here: End User License Agreement. Copyright infringement is a violation of federal law subject to criminal and civil penalties. WFCM Wood Frame Construction Manual for One- and Two-Family Dwellings 015 EDITION ANSI/AWC WFCM-015 Approval date October 10, 014 10
GENERAL INFORMATION 015 WFCM Table 1 Applicability Limitations Attribute Limitation Reference Section Figures 1.1.3.1a 1.1.3.1a 1.1.3.1b 1. Ͳ Ͳ BUILDING DIMENSIONS Mean Roof Height (MRH) Number of Stories Building Length and Width 33' 3 80' LOAD ASSUMPTIONS (See Chapter or Chapter 3 tables for load assumptions applicable to the specific tabulated requirement) Load Assumption Load Type 0Ͳ8 psf of floor area Partition Dead Load 11Ͳ18 psf Wall Assembly Dead Load 10Ͳ0 psf Floor Dead Load Roof/Ceiling Assembly Dead Load 0Ͳ5 psf Floor Live Load 30Ͳ40 psf Roof Live Load 0 psf Ceiling Live Load 10Ͳ0 psf Ground Snow Load 0Ͳ70 psf Wind Load Seismic Load 110Ͳ195 mph wind speed (700Ͳyr. return period, 3Ͳsecond gust) Exposure B, C, and D Seismic Design Category (SDC) SDC A, B, C, D0, D1, and D AMERICAN WOOD COUNCIL 11
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM ENGINEERED DESIGN.1 General Provisions 15. Connections 17.3 Floor Systems 19.4 Wall Systems 1.5 Roof Systems 3 List of Figures 6 List of Tables 61 Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 1
ENGINEERED DESIGN 015 WFCM Table Engineered Design Limitations Limitation Reference Section Figures 33' 3 80'.1.3.1 1.1.3.1a 1.1.3.1b 1. 6' 4" o.c. d.1.3.a.1.3.b.1.3.c.1a d 6' 4" o.c. (see manufacturer).1.3.d.1.3.a.1.3.b.3..6 (see manufacturer) 6' 4" o.c. (see truss plans) (see truss plans) df.3..5.1.3.a.1.3.b.3.3.6.3.3.5.1d.4e,.9a,.9b.4d.13a,.13b.1.3.e.1i 4:1.1.3.f.1.3.g.1j.1k.1.3.3a.1.3.3a.1.3.3b.1l Attribute BUILDING DIMENSIONS Building Lumber Joists Wood IJoists Mean Roof Height (MRH) Number of Stories Building Length and Width FLOOR SYSTEMS Joist Span Joist Spacing Cantilevers Supporting loadbearing Setbacks Loadbearing walls1 IJoist Span IJoist Spacing Cantilevers Setbacks Wood Floor Trusses Truss Span Truss Spacing Cantilevers Setbacks Floor Diaphragms Vertical Floor Offset1 1 Floor Diaphragm Aspect Ratio Floor Diaphragm Openings Wall Studs Loadbearing Wall Height NonLoadbearing Wall Height Wall Stud Spacing Shear Walls Shear Wall Line Offset1 Lesser of 1' or 50% of Building Dimension WALL SYSTEMS 0' 0' 4" o.c. 1 Shear Wall Story Offset Shear Wall Segment Aspect Ratio 4'.1.3.3c No offset unless per Exception (see SDPWS ).1.3.3d.1.3.3e ROOF SYSTEMS Lumber Rafters Rafter Span (Horizontal Projection) Rafter Spacing Eave Overhang Length1 Roof Slope Wood IJoist Roof IJoist Span IJoist Spacing System Eave Overhang Length Roof Slope Wood Roof Trusses Truss Span Truss Spacing Eave Overhang Length Roof Slope Rakes Overhang Length1 Roof Diaphragms Roof Diaphragm Aspect Ratio1 1 See exceptions. For roof snow loads, tabulated spans are limited to 0 ft. 6' 4" o.c. Lesser of ' or rafter span/3 Flat 1:1 6' 4" o.c. (see manufacturer) Flat 1:1 60' 4" o.c. (see truss plans) Flat 1:1 Lesser of ' or purlin span/3 4:1.1.3.4a.1.3.4b.5.1.1..1.3.4d.1.3.4a.1.3.4b.5..1..1.3.4d.1.3.4a.1.3.4b.5.3.1.1.3.4d.1.3.4c.1.3.4e.1f.1g.1j Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 13
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM.3.3.3 End Restraint.3.3.4 Chord and Web Bracing Chord and web bracing shall be provided in a manner consistent with the guidelines provided in BCSI, ANSI/TPI 1, or in accordance with.3.3.1, and the bracing requirements specified in the construction design documents (see Figure.14)..3.4. Shear Capacity Floor sheathing and fasteners shall be capable of resisting the total shear loads calculated using Tables.5A and.5b for wind perpendicular and parallel to ridge respectively, or using Table.6 for seismic motion..3.4..1 Diaphragm Chords Diaphragm chords shall be continuous for the full length of the diaphragm. Diaphragm members and chord splices shall be capable of resisting the chord forces, calculated by the following equation: T= vl 4 where:.3.3.5 Single or Continuous Floor Trusses Supporting Walls (.3-1) T = Chord force, lbs v = Required unit shear capacity of the floor diaphragm, plf Floor trusses shall be designed for any intermediate loads and supports as shown on the construction documents and/or plans. L = Floor diaphragm dimension perpendicular to the lateral load, ft.3.4.3 Sheathing Edge Support.3.3.6 Cantilevered Trusses Cantilevered floor trusses shall be designed for all anticipated loading conditions (see Figures.13a-b)..3.3.7 Floor Openings Framing around floor openings shall be designed to transfer loads to adjacent framing members that are designed to support the additional concentrated loads. Fasteners, connections, and stiffeners shall be designed for the loading conditions..3.4 Floor Sheathing.3.4.1 Sheathing Spans Edges of floor sheathing shall have approved tongueand-groove joints or shall be supported with blocking, unless 1/4-inch minimum thickness underlayment or 1-1/ inches of approved cellular or lightweight concrete is installed, or unless the finish floor is of 3/4-inch wood strip..3.5 Floor Diaphragm Bracing At panel edges perpendicular to floor framing members, framing and connections shall be provided to transfer the lateral wind loads from the exterior wall to the floor diaphragm assembly in accordance with the requirements of Table.1 (see Figure.3). Floors shall be fully sheathed with sheathing capable of resisting and transferring the applied gravity loads to.4 Wall Systems.4.1 Exterior Walls.4.1.1 Wood Studs Exterior wall studs shall be in accordance with the requirements of Table.9A or Table.10 for the wind loads specified. Exterior loadbearing studs shall be in accordance with the requirements of Table.9B or Table.11 for the gravity loads specified. Exterior loadbearing studs shall be designed to resist the uplift loads specified in Table.A, independent of the requirements of Tables.9A,.9B,.10, and.11. Exterior non-loadbearing studs shall be designed to resist the rake overhang uplift loads specified in Table.C..4.1.1.1 Notching and Boring Notches in either edge Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 14 ENGINEERED DESIGN Restraint against twisting shall be provided at the end of each truss by fastening to a full-height rim, band joist, header, or other member or by using blocking panels between truss ends. Framing details (see Figure.15a) for end restraint shall be provided in a manner consistent with SBCA/TPI s Building Component Safety Information (BCSI) Guide to Good Practice for Handling, Installing, Restraining, & Bracing of Metal Plate Connected Wood Trusses, or ANSI/TPI 1, or.3.3.1. the floor framing members. Sheathing shall be continuous over two or more spans.
ENGINEERED DESIGN 015 WFCM of studs shall not be located in the middle one-third of the stud length. Notches in the outer thirds of the stud length shall not exceed 5% of the actual stud depth. Bored holes shall not exceed 40% of the actual stud depth and the edge of the hole shall not be closer than 5/8-inch to the edge of the stud. Notches and holes shall not occur in the same cross-section (see Figure 3.3b). EXCEPTION: Bored holes shall not exceed 60% of the actual stud depth when studs are doubled..4.1.1. Stud Continuity Studs shall be continuous between horizontal supports, including but not limited to: girders, floor diaphragm assemblies, ceiling diaphragm assemblies, and roof diaphragm assemblies. Where attic floor diaphragm or ceiling diaphragm assemblies are used to brace gable endwalls, the sheathing and fasteners shall be capable of resisting the minimum shear requirements of Table.5C..4.1.1.3 Corners Corner framing shall be capable of transferring axial tension and compression loads from the shear walls and the structure above, connecting adjoining walls, and providing adequate backing for the attachment of sheathing and cladding materials..4.1. Top Plates Exterior stud walls shall be capped with a single or double top plate with bearing capacity in accordance with Table.9B, and bending capacity in accordance with Table.11. Top plates shall be tied at joints, corners, and intersecting walls to resist and transfer lateral loads to the roof or floor diaphragm in accordance with the requirements of Table.1. Double top plates shall be lap spliced and overlap at corners and intersections with other exterior and interior loadbearing walls..4.1.3 Bottom Plate Wall studs shall bear on a bottom plate with bearing capacity in accordance with Table.9B. The bottom plate shall not be less than inch nominal thickness and not less than the width of the wall studs. Studs shall have full bearing on the bottom plate. Bottom plates shall be connected to transfer lateral loads to the floor diaphragm or foundation in accordance with the requirements of Table.1. Bottom plates that are connected directly to the foundation shall have full bearing on the foundation..4.1.4 Wall Openings Headers shall be provided over all exterior wall openings. Headers shall be supported by wall studs, jack studs, hangers, or framing anchors..4.1.4.1 Headers Headers shall be in accordance with the lateral capacity requirements of Table.1 and the gravity capacity requirements of Table.11..4.1.4. Studs Supporting Header Beams Wall and jack studs shall be in accordance with the same requirements as exterior wall studs selected in.4.1.1. Wall and jack studs shall be designed for additional lateral and uplift loads from headers and window sill plates in accordance with Table.1 and Table.A..4.1.4.3 Window Sill Plates Window sill plates shall be in accordance with the lateral capacity requirements of Table.1..4. Interior Loadbearing Partitions.4..1 Wood Studs Interior loadbearing studs shall be in accordance with the requirements of Table.9C or Table.11 for gravity loads..4..1.1 Notching and Boring Notches in either edge of studs shall not be located in the middle one-third of the stud length. Notches in the outer thirds of the stud length shall not exceed 5% of the actual stud depth. Bored holes in interior loadbearing studs shall not exceed 40% of the actual stud depth and shall not be closer than 5/8-inch to the edge. Notches and holes shall not occur in the same cross-section (see Figure 3.3b). EXCEPTION: Bored holes shall not exceed 60% of the actual stud depth when studs are doubled..4..1. Stud Continuity Studs shall be continuous between horizontal supports, including but not limited to: girders, floor diaphragm assemblies, ceiling diaphragm assemblies, and roof diaphragm assemblies..4.. Top Plates Interior loadbearing partition walls shall be capped with a single or double top plate with bearing capacity in accordance with Table.9C, and bending capacity in accordance with Table.11. Top plates shall be tied at joints, corners, and intersecting walls. Double top plates shall be lap spliced and overlap at corners and at intersections with other exterior and interior loadbearing walls..4..3 Bottom Plate Wall studs shall bear on a bottom plate with bearing capacity in accordance with Table.9C. The bottom plate shall not be less than inch nominal thickness and not less than the width of the wall studs. Studs shall have full bearing on the bottom plate. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 15
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM List of Tables Lateral Framing Connection Loads from Wind... 6.10 Exterior Wall Induced Moments from Wind Loads... 85.A Uplift Connection Loads from Wind... 63.11.B Ridge Connection Loads from Wind... 64 Loadbearing Wall Loads from Snow or Live Loads... 86.C Rake Overhang Outlooker Uplift Connection Loads... 65.3 Thrust Connection Loads... 66.4 Roof and Wall Sheathing Suction Loads... 67.5A Lateral Diaphragm Loads from Wind Perpendicular to Ridge... 68.5B Lateral Diaphragm Loads from Wind Parallel to Ridge... 69.5C Lateral Diaphragm Loads from Wind Parallel to Ridge (Attic/Floor/Ceiling)... 71.6 Lateral Loads from Seismic... 73.7A Floor Joist Spans for 30 psf Live Load... 74.7B Floor Joist Spans for 40 psf Live Load... 75.7C Floor Joist Bearing Stresses for Floor Loads... 76.8A Floor Framing Capacity Requirements for 30 psf Live Load... 77.8B Floor Framing Capacity Requirements for 40 psf Live Load... 78.9A Exterior Wall Stud Bending Stresses from Wind Loads... 80.9B Exterior Wall Stud Compression Stresses... 8.9C Interior Loadbearing Wall Stud Compression Stresses from Live Loads... 84 ENGINEERED DESIGN.1.1A1- Ceiling Joist Spans for 10 psf Live Load... 87.1B1- Ceiling Joist Spans for 0 psf Live Load... 89.13A1- Ceiling Joist Framing Capacity Requirements (without storage)... 91.13B1- Ceiling Joist Framing Capacity Requirements (with limited storage)... 93.14A Rafter Spans for 0 psf Live Load... 96.14B Rafter Spans for 30 psf Ground Snow Load... 99.14C Rafter Spans for 50 psf Ground Snow Load... 100.14D Rafter Spans for 70 psf Ground Snow Load... 101.15A Roof Framing Capacity Requirements for 0 psf Roof Live Load... 103.15B Roof Framing Capacity Requirements for 30 psf Ground Snow Load... 106.15C Roof Framing Capacity Requirements for 50 psf Ground Snow Load... 107.15D Roof Framing Capacity Requirements for 70 psf Ground Snow Load... 108.16 Ridge Beam Capacity Requirements for Interior Center Bearing Roof and Ceiling.. 110.17 Hip and Valley Beam Capacity Requirements...111 Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 16
ENGINEERED DESIGN 015 WFCM Table.1 Lateral Framing Connection Loads from Wind (For Roof-to-Plate, Plate-to-Plate, Plate-to-Stud, and Plate-to-Floor) 700yr. Wind Speed 3second gust (mph) 110 115 10 130 140 150 160 170 180 195 Unit Framing Loads (plf)1,,3,4 67 73 79 93 108 14 141 159 178 09 8 10 79 87 94 111 19 148 168 190 1 49 1 91 100 109 18 148 170 193 18 45 87 14 103 11 1 144 167 191 18 46 75 33 16 114 14 135 159 184 1 41 7 305 358 18 14 136 148 174 01 31 63 97 333 391 0 135 147 160 188 18 50 85 31 360 43 Tabulated framing loads shall be permitted to be multiplied by 0.9 for framing not located within 3 feet of corners for buildings less than 30 feet in width (W), or within W/10 of corners for buildings greater than 30 feet in width. Wall Height (ft) 1 3 4 Tabulated framing loads assume a building located in Exposure B with a mean roof height of 33 feet. For buildings located in other exposures, tabulated values shall be multiplied by the appropriate adjustment factor in Section.1.3.1. Tabulated framing loads are specified in pounds per linear foot of wall. To determine connection requirements, multiply the tabulated unit lateral framing load by the multiplier from the table below corresponding to the spacing of the connection: 1 16 19. 4 48 Connection Spacing (in.) 1.00 1.33 1.60.00 4.00 Multiplier When calculating lateral loads for ends of headers, girders, and window sills, multiply the tabulated unit lateral load by ½ of the header, girder, or sill span (ft). Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 17
COMMENTARY TO THE WOOD FRAME CONSTRUCTION MANUAL WFCM Commentary Table.1 Description: Procedure: Lateral Framing Connection Loads from Wind Lateral framing connection loads at base and top of wall expressed in pounds per linear foot of wall length. The internal pressure coefficient (GCpi) is taken from ASCE 7-10 Table 6.11-1. Compute the lateral framing connection load at the top and bottom of studs based on tributary wind loads, using external (end zone) components and cladding pressure coefficients and internal pressure coefficients for enclosed buildings. therefore: Example: Given -150 mph, Exposure B, 33' MRH, 10' wall height, 16" o.c. connection spacing. where: pmax = qgcp - qgcpi ENGINEERED DESIGN Background: Components and cladding (C&C) coefficients result in higher wind loads relative to main wind force resisting system (MWFRS) coefficients. When determining C&C pressure coefficients (GCp), the effective wind area equals the tributary area of the framing member. For long and narrow tributary areas, the area width may be increased to one-third the framing member span to account for actual load distributions. This results in lower average wind pressures. The increase in width applies only to calculation of wind force coefficients. GCpi = +/- 0.18 pmax = 1.15 (-1. - 0.18) = -9.61 psf (Negative pressure denotes suction) The pressure is multiplied by half the stud height to obtain the unit lateral framing connection load: = -9.61(10/) = -148 plf (WFCM Table.1) Required capacity of lateral framing connections spaced at 16" o.c. is: = 148plf (16 in./1 in./ft) = 197 lbs = 148 (1.33) (WFCM Table.1 Footnote 3) Footnote 1: Lateral framing connection loads are based on End Zone Coefficients (Zone 5) per the figure of Table.4. Where Interior Zones (Zone 4) occur, connection loads may be reduced. Adjustment of tabulated loads are conservatively based on a 0' wall height where A = 133 ft. End Zone pmax = pressure on the wall GCp = -0.8-0.6[(log(A/500)) / (log (10/500))] q = 1.15 psf (See Table C1.1) = -0.8-0.6[(log(133/500)) / (log(10/500))] GCp = external pressure coefficients for C&C = -1.00 GCpi = +/- 0.18 internal pressure coefficient for enclosed buildings Interior Zone Stud tributary area equals 13.3 ft. The minimum required area for analysis is h/3=33.3 ft. The GCp equation is determined using ASCE 7-10 Figure 30.4-1. End Zones (See Zone 5 as shown in WFCM Table.4): GCp = -1.4 for A 10 ft GCp = -0.8-0.6[(log(A/500)) / (log (10/500))] for 10 < A 500 ft GCp = -0.8 for A > 500 ft therefore: GCp = -0.8-0.3[(log(A/500)) / (log(10/500))] = -0.8-0.3[(log(133/500)) / (log(10/500))] = -0.9 The ratio of Zone 4 to Zone 5 loads is: (-0.9-0.18) / (-1.0-0.18) = 0.9 (WFCM Table.1 Footnote 1) Therefore, Interior Zone loads may be reduced to 9% of tabulated values. GCp = -0.8-0.6[(log(33.3/500)) / (log (10/500))] GCp = -1. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 18
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM Table.9A 700yr. Wind Speed 3second gust (mph) Stud Size 8 ft 10 ft 1 ft 14 ft 16 ft 18 ft 0 ft 1 3 Stud Spacing 150 x4 x6 160 x8 x4 x6 170 x8 x4 x6 180 x8 x4 x6 195 x8 x4 x6 x8 ENGINEERED DESIGN Wall Height Exterior Wall Stud Bending Stresses from Wind Loads (Cont.) Induced fb (psi)1,,3 1 in. 903 366 11 108 416 40 1160 470 70 1301 57 303 157 618 356 16 in. 105 488 81 1371 555 319 1547 67 361 1735 70 404 036 84 474 4 in. 1807 73 41 056 833 479 31 940 541 60 1054 606 3054 137 71 1 in. 1365 553 318 1553 69 36 1754 710 409 1966 796 458 307 934 538 16 in. 180 737 44 071 839 483 338 947 545 61 106 611 3077 146 717 4 in. 731 1106 636 3107 158 74 3507 140 817 393 159 916 4615 1869 1076 1 in. 1906 77 444 168 878 505 448 991 570 744 1111 640 30 1304 751 16 in. 541 109 59 891 1171 674 363 13 761 3659 148 853 494 1739 1001 4 in. 3811 1543 888 4336 1756 1011 4895 198 1141 5488 179 608 1501 1 in. 519 100 587 866 1161 668 336 1310 754 368 1469 845 458 174 99 16 in. 3359 1360 783 38 1548 891 4314 1747 1006 4837 1959 117 5677 99 133 4 in. 5039 040 1174 5733 3 1336 61 1508 938 1691 3448 1985 1 in. 303 197 746 3644 1476 849 4113 1666 959 461 1868 1075 541 19 161 16 in. 470 179 995 4858 1967 113 5485 1 178 490 1433 9 168 4 in. 594 1493 951 1698 333 1917 3735 150 4383 53 1 in. 395 1600 91 4496 181 1048 5076 056 1183 5691 304 136 705 1556 16 in. 569 134 18 5995 48 1397 741 1577 3073 1768 3606 075 4 in. 301 184 364 096 4111 366 4609 65 5409 3113 1 in. 4764 199 1110 540 195 163 478 146 778 1599 360 1876 16 in. 57 1480 97 1684 3304 1901 3704 13 4347 50 4 in. 3859 1 4390 57 4956 85 5556 3198 3753 Tabulated bending stresses assume a building located in Exposure B with a mean roof height of 33 feet. For buildings located in other exposures, the tabulated values shall be multiplied by the appropriate adjustment factor in Section.1.3.1. Tabulated bending stresses shall be permitted to be multiplied by 0.9 for framing not located within 3 feet of corners for buildings less than 30 feet in width (W), or within W/10 of corners for buildings greater than 30 feet in width. The tabulated bending stress (fb) shall be less than or equal to the allowable bending design value (Fb'). Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 19
COMMENTARY TO THE WOOD FRAME CONSTRUCTION MANUAL WFCM Commentary Table.9A Exterior Wall Stud Bending Stresses from Wind Loads Description: Bending stress in wall studs due to wind load. Procedure: Compute wind pressures using C&C coefficients and calculate stud requirements. Given - 150 mph, Exposure B, 33' MRH, 10' wall height, x4 studs, 16" o.c. stud spacing. Calculations from Table.10 for exterior wall induced moments from wind loads showed the applied bending moment for this case to be 464.6 ft-lbs. ENGINEERED DESIGN Background: As in Table.4, peak suction forces are very high. Defining the effective wind area and the tributary area of the wall stud is key to computing the design suction. Stud span equals the wall height minus the thickness of the top and bottom plates. For a nominal 8' wall, the height is: 97 1/8" - 4.5" = 9 3/8". Two cases have been checked in these tables. For C&C wind pressures, the bending stresses are computed independent of axial stresses. In addition, the case in which bending stresses from MWFRS pressures act in combination with axial stresses from wind and gravity loads must be analyzed. For buildings limited to the conditions in this Manual, the C&C loads control the stud design. Example: Substituting this bending moment into a bending stress calculation: fb = M(tabulated)/S = 464.6 (1)/3.065 = 1,80 psi fb (Tabulated) = 1,80 psi (WFCM Table.9A) Footnote : See Commentary Table.1 for calculation of footnotes. Considerations in Wind Design of Wood Structures http://awc.org/pdf/codes-standards/publications/archives/awc-considerations-0310.pdf Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 0
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM Table.10 Exterior Wall Induced Moments from Wind Loads 700yr. Wind Speed 3second gust (mph) Wall Height 10 ft 1 ft 14 ft 16 ft 18 ft 0 ft 1 115 10 130 140 150 160 170 180 195 Induced Moment (ftlbs)1, ENGINEERED DESIGN 8 ft Stud Spacing 110 1 in. 14 136 148 173 01 31 6 96 33 390 16 in. 165 181 197 31 68 307 350 395 443 50 4 in. 48 71 95 346 40 461 55 59 664 779 1 in. 187 05 3 6 304 348 396 448 50 589 16 in. 50 73 97 349 405 465 59 597 669 785 4 in. 375 410 446 53 607 697 793 895 1004 1178 1 in. 6 86 311 365 44 486 553 65 700 8 16 in. 349 381 415 487 565 648 738 833 934 1096 4 in. 53 57 6 731 847 973 1107 149 1401 1644 1 in. 346 378 411 483 560 643 73 86 96 1087 16 in. 461 504 549 644 747 857 975 1101 134 1449 4 in. 69 756 83 966 110 186 1463 165 185 173 1 in. 440 480 53 614 71 817 930 1050 1177 1381 16 in. 586 641 697 819 949 1090 140 1400 1569 184 4 in. 879 961 1046 18 144 1635 1860 100 354 763 1 in. 54 593 645 758 879 1009 1147 195 145 1704 16 in. 73 790 861 1010 1171 1345 1530 177 1936 73 4 in. 1085 1186 191 1515 1757 017 95 591 905 3409 1 in. 654 715 778 913 1059 116 1383 156 1751 055 16 in. 87 953 1038 118 141 161 1844 08 334 740 4 in. 1308 149 1556 186 118 43 767 313 350 4110 Tabulated induced moments assume a building located in Exposure B with a mean roof height of 33 feet. For buildings located in other exposures, the tabulated values shall be multiplied by the appropriate adjustment factor in Section.1.3.1. Tabulated induced moments shall be permitted to be multiplied by 0.9 for framing not located within 3 feet of corners for buildings less than 30 feet in width (W), or within W/10 of corners for buildings greater than 30 feet in width. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 1
ENGINEERED DESIGN WFCM Commentary Table.10 Exterior Wall Induced Moments From Wind Loads Description: Applied moment on wall due to wind loads. Procedure: Calculate the applied moment based on C&C wind pressures. Background: Applied suction force is dependent on tributary areas. Substituting this uniform load, w, into a bending calculation for a simply supported member: wl M= 8 Example: = Given - 150 mph, Exposure B, 33' MRH, 10' wall height, 16" o.c. stud spacing. pmax = 9.61 psf (See Commentary to Table.1) w = pmax (16 in./1in./ft) = 39.48 plf ( 39.48) (10 3.375 ) 1 8 = 466 ft lbs M(Tabulated) = 466 ft-lbs (A value of 465ft-lbs is shown in WFCM Table.10 difference due to rounding in calculation of pmax) Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL
ENGINEERED DESIGN 015 WFCM Table.9B Exterior Wall Stud Compression Stresses Dead Load Assumptions: Roof Assembly DL = 0 psf, Wall Assembly DL = 11 plf, Floor Assembly DL = 10 psf, Floor LL = 40 psf Ground Snow Load or Roof Live Load Loadbearing Wall Supporting Stud Stud Spacing Size 0 psf RLL 1 4 36 30 psf GSL 60 1 4 50 psf GSL Building Width (ft) 36 60 1 4 36 70 psf GSL 60 1 4 36 60 Induced fc (psi)1 x4 84 130 175 67 9 140 188 86 117 18 47 380 14 4 307 473 x6 53 83 11 170 58 89 10 18 74 116 157 4 91 143 195 301 x8 41 63 85 19 44 67 91 138 56 88 119 183 69 108 148 9 x4 11 173 34 356 1 186 51 381 156 43 330 506 190 99 409 631 16 in. x6 71 110 149 6 78 119 160 4 99 154 10 3 11 190 60 40 x8 54 83 113 17 59 90 11 184 75 117 159 44 9 144 197 305 x4 168 59 351 534 183 79 376 57 34 364 495 85 448 613 4 in. x6 107 165 3 340 117 178 39 364 149 3 315 483 181 85 390 603 x8 81 15 169 58 88 135 18 76 113 176 39 367 138 16 96 457 x4 61 84 107 153 73 100 18 17 93 131 171 30 113 16 13 91 Center x6 39 53 68 97 46 64 8 109 59 84 109 147 7 103 136 185 Bearing Roof 1 in. x8 30 41 5 74 35 48 6 83 45 63 8 111 55 78 103 141 & Ceiling x4 8 11 14 03 97 134 171 9 14 175 8 307 151 17 84 388 16 in. x6 5 71 91 19 6 85 109 146 79 111 145 196 96 138 181 47 x8 39 54 69 98 47 64 83 111 60 85 110 148 73 105 137 187 x4 1 168 14 305 145 00 57 344 186 63 34 461 6 35 46 58 4 in. x6 78 107 136 194 9 18 163 19 118 167 17 93 144 07 71 371 x8 59 81 103 147 70 97 14 166 90 17 165 3 109 157 06 81 x4 1 185 48 374 18 193 58 388 147 4 30 458 171 59 347 59 Roof, Ceiling, 1 in. x6 78 118 158 38 81 13 164 47 94 143 19 9 109 165 1 336 & 1 Center x8 59 89 10 180 6 93 14 187 71 108 146 1 83 15 167 55 Bearing Floor x4 163 47 331 498 171 57 343 517 196 99 403 611 8 345 46 16 in. x6 104 157 10 317 109 163 19 39 15 190 56 389 145 19 94 449 x8 79 119 160 41 8 14 166 50 95 144 194 95 110 166 3 340 x4 45 370 496 56 385 515 94 449 604 34 517 4 in. x6 156 36 316 476 163 45 38 494 187 85 384 583 18 39 441 x8 118 179 39 361 14 186 49 375 14 17 9 44 165 50 335 510 x4 145 31 317 488 151 38 36 50 170 70 371 573 189 30 415 643 Roof, Ceiling, 1 in. x6 9 147 01 311 96 15 08 30 108 17 36 364 10 19 64 409 & 1 Clear Span x8 70 111 153 36 73 115 157 4 8 130 179 76 91 146 00 310 Floor x4 194 308 4 651 01 318 435 7 360 494 5 40 553 16 in. x6 13 196 69 414 18 0 77 46 144 9 314 486 160 56 35 546 x8 93 149 04 314 97 153 10 33 109 174 39 369 1 194 67 414 x4 90 46 633 30 477 65 340 540 378 603 4 in. x6 185 94 403 61 19 303 415 639 16 344 47 40 384 58 x8 140 3 306 471 146 30 315 485 164 61 358 553 18 91 401 61 x4 10 145 188 74 111 157 04 88 16 181 36 33 14 04 68 378 Center 1 in. x6 65 9 10 174 71 100 130 183 80 115 150 11 90 130 170 40 Bearing Roof, x8 49 70 91 13 54 76 99 139 61 87 114 160 69 98 19 18 Ceiling, & 1 x4 136 194 51 365 148 10 7 384 168 41 315 443 189 7 357 503 Floor 16 in. x6 87 13 160 3 94 133 173 45 107 153 00 8 10 173 7 30 x8 66 93 11 176 71 101 131 186 81 116 15 14 91 131 17 43 x4 05 90 376 547 315 408 576 5 361 47 84 408 535 4 in. x6 130 185 39 348 141 00 60 367 160 30 300 43 181 60 341 481 x8 99 140 18 64 107 15 197 78 1 174 8 31 137 197 58 365 1 Tabulated compression stresses (fc) shall be less than or equal to the allowable compression perpendicular to grain design value (Fc ') for top and bottom plates, and less than or equal to the allowable compression parallel to grain design value (FcII') for studs. Roof & Clear Span Ceiling 1 in. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 3
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM Table.9B Exterior Wall Stud Compression Stresses (Cont.) Dead Load Assumptions: Roof Assembly DL = 0 psf, Wall Assembly DL = 11 plf, Floor Assembly Dead Load Assumptions: Assembly DL == 0 DL = Roof 10 psf, Floor LL 40psf, psfwall Assembly DL = 11 plf, Floor Assembly DL = 10 psf, Floor LL = 40 psf Ground Snow Load or Roof Live Load Roof, Ceiling, & Center Bearing Floors Roof, Ceiling, & Clear Span Floors Center Bearing Roof, Ceiling, & Floors 1 Stud Stud Spacing Size 1 4 36 30 psf GSL 60 1 4 50 psf GSL Building Width (ft) 36 60 1 4 36 70 psf GSL 60 1 4 36 60 ENGINEERED DESIGN Loadbearing Wall Supporting 0 psf RLL 1 Induced fc (psi) x4 168 54 340 511 174 61 349 55 193 93 394 596 1 35 438 x6 107 16 16 35 111 166 334 13 187 50 379 135 07 79 44 x8 81 13 164 47 84 16 169 54 93 141 190 88 10 157 11 3 x4 4 339 453 3 349 466 57 391 55 83 433 584 x6 143 15 88 434 148 96 446 164 49 334 505 180 76 37 565 16 in. x8 108 163 19 39 11 168 5 338 14 189 53 383 136 09 8 49 x4 336 508 348 53 386 586 44 649 x6 14 33 43 650 1 333 444 46 373 501 70 413 557 4 in. x8 16 45 38 493 168 5 337 507 186 83 380 575 05 314 43 643 x4 14* 351* 488* 0 353 488* 39 385 531 58 416 575 x6 136* 3* 311* 485* 140 5 311* 485* 15 45 338 54 164 65 366 569 1 in. x8 103* 169* 36* 368* 106 170 36* 368* 115 186 56 398 14 01 78 43 x4 85* 468* 651* 93 470 651* 318 513 344 555 x6 181* 98* 414* 647* 186 99 414* 647* 03 36 450 19 353 488 16 in. x8 138* 6* 314* 491* 141 7 314* 491* 154 47 34 531 166 68 370 576 x4 48* 439 477 515 x6 7* 447* 61* 80 449 61* 304 489 38 530 4 in. x8 07* 339* 471* 1 341 471* 30 371 51 49 40 555 x4 148 14 8 40 157 6 96 46 17 49 38 469 187 73 359 515 x6 94 136 180 67 100 144 188 71 109 159 08 99 119 174 9 38 1 in. x8 7 103 136 03 76 109 143 05 83 10 158 7 90 13 173 49 x4 198 85 377 559 09 301 394 567 9 333 437 66 50 364 479 x6 16 181 40 356 133 19 51 361 146 1 78 398 159 31 305 437 16 in. x8 95 138 18 70 101 146 190 74 111 161 11 30 11 176 31 331 x4 96 48 565 314 45 59 344 499 655 374 545 x6 189 7 360 534 00 88 376 54 19 317 417 598 38 347 457 655 4 in. x8 143 07 73 405 151 18 86 411 166 41 316 453 181 63 347 497 Tabulated compression stresses (fc) shall be less than or equal to the allowable compression perpendicular to grain design value (Fc ') for top and bottom plates, and less than or equal to the allowable compression parallel to grain design value (Fc ') for studs. 1 in. * Tabulated compression stresses are based on the maximum load combination: Dead Load + Floor Live Load (i.e. D + L). Reduced unit loads are permitted for load combinations that include Roof Live Load (RLL) and Ground Snow Load (GSL). Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 4
ENGINEERED DESIGN WFCM Commentary Table.9B Exterior Wall Stud Compression Stresses Description: Direct compression stress in wall studs under live load. Procedure: Sum gravity loads and calculate stud requirement. Background: See Commentary for Table.11. Calculate the compression load: P = wtotal (1 in./1) wheader =,665 plf (from Table.11) wwall = 11 psf (11 ft) = 11 plf Example: wtotal =,665 plf + 11 plf =,786 plf P =,786 (1 in./1in./ft) =,786 lbs Calculate compression stress: fc = P / A =,786 / 8.5 = 338 psi (WFCM Table.9B) Given - loadbearing wall supporting Roof, Ceiling, & Clear Span Floors, 36' building width, ' overhangs, x6 studs, 1" o.c. stud spacing, 11 plf wall dead load, 0 psf roof dead load, 40 psf floor live load, and 50 psf ground snow load. Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 5
ENGINEERED DESIGN 015 WFCM Table.11 Loadbearing Wall Loads from Snow or Live Loads (For Wall Studs, Headers, and Girders) Dead Load Assumptions: Roof Assembly DL = 0 psf, Wall Assembly DL = 11 plf, Floor Assembly DL = 10 psf, Floor LL = 40 psf Ground Snow Load or Roof Live Load (psf) GSL RLL 0 30 50 70 30 560 800 180 1 4 36 60 GSL RLL 0 30 50 360 613 867 1379 Ground Snow Load or Roof Live Load (psf) 30 50 70 0 0 Unit Header/Girder Beam Loads (plf) 67 00 60 367 473 40 1056 30 405 568 73 480 1489 440 553 776 998 70 365 680 78 1089 1407 100 GSL RLL 70 493 834 1178 187 30 50 GSL RLL 70 30 50 70 59 517 776 193 351 70 1053 1755 443 887 1330 17 0 30 50 GSL RLL 70 0 GSL RLL 30 50 70 461 705 951 139 541 87 1118 163 64 950 184 186 0 30 50 70 1 Roof Span (ft) 1 4 36 60 0 GSL RLL 1 Roof Span (ft) Ground Snow Load or Roof Live Load (psf) GSL RLL 641 671 771 871 1091 1130 197 1463 1541 1591 184 058 441 515 885 355 RLL 0 50 551 890 131 1915 RLL GSL 30 51 851 1181 1841 70 0 651 1057 1464 85 Unit Header/Girder Beam Loads (plf) 778 300* 300* 300* 300* 416 137 600* 600* 600* 600* 641 1700 900* 900* 900* 900* 866 655 1500* 1500* 1500* 1500* 1316 RLL GSL 30 50 70 0 RLL GSL 30 50 70 0 RLL GSL 30 50 571 585 654 74 101 1049 1188 136 1471 1513 171 199 371 441 787 3134 70 0 GSL 30 50 70 1 Roof Span (ft) Unit Header/Girder Beam Loads (plf) 100* 103 113 13 76 79 89 99 71* 71* 71* 71* 657 70 78 86 96* 96* 1015 1085 1 4 17* 1731 1898 064 11 151 1418 1584 131* 131* 131* 131* 100 1066 1188 1311 168* 168* 1789 197 36 44* 44* 665 899 166 171 1945 179 191* 191* 191* 191* 136 143 1599 1765 40* 40* 56 770 60 388* 388* 406 4576 56 636 3006 3376 311* 311* 311* 311* 08 113 344 583 384* 384* 4108 4455 1 Tabulated loads assume simplyͳsupported single span floor joists. For continuous two span floor joists, loads on interior loadbearing walls, headers, and girders shall be multiplied by 1.5. * Tabulated unit header/girder beam loads (plf) are based on the maximum load combination: Dead Load + Floor Live Load (i.e. D + L). Reduced unit loads are permitted for load combinations that include Roof Live Load (RLL) and Ground Snow Load (GSL). AMERICAN WOOD COUNCIL 6
COMMENTARY TO THE WOOD FRAME CONSTRUCTION MANUAL WFCM Commentary Table.11 Loadbearing Wall Loads From Snow or Live Loads (For Wall Studs, Headers, and Girders) Gravity loads on walls, headers, and girdhuv IRU VWRU\ EXLOGLQJ FRQ JXUDWLRQV Procedure: Sum gravity loads and calculate wall and KHDGHU JLUGHU UHTXLUHPHQWV Table.11, the following ASCE 7-10 load combinations were considered. When designing structural wood members, it is also necessary to consider the effect of ORDG GXUDWLRQ DV IROORZV Background: In calculating the unit header/girder beam ORDGV IRU HDFK EXLOGLQJ FRQ JXUDWLRQ LQ ENGINEERED DESIGN Description: 'ŽǀĞƌŶŝŶŐ >ŽĂĚ ƵƌĂƟŽŶ D ƚž ďğ ƉƉůŝĞĚ ŝŷ ĞƐŝŐŶŝŶŐ ^ƚƌƶđƚƶƌăů tžžě DĞŵďĞƌƐ ^ ϳͲϭϬ ^ >ŽĂĚ ŽŵďŝŶĂƟŽŶƐ #1 ĞĂĚ н ZŽŽĨ >ŝǀğ 1.5 # ĞĂĚ н &ůžžƌ >ŝǀğ 1.00 #3 ĞĂĚ н ^ŶŽǁ 1.15 #4 ĞĂĚ н Ϭ ϳϱ &ůžžƌ >ŝǀğ н Ϭ ϳϱ ZŽŽĨ >ŝǀğ 1.5 #5 ĞĂĚ н Ϭ ϳϱ &ůžžƌ >ŝǀğ н Ϭ ϳϱ ^ŶŽǁ 1.15 $V D UHVXOW RI WKH IDFWRU XVHG LQ ORDG FRPELQDWLRQV DQG DERYH VHYHUDO RI WKH PXOWL VWRU\ FDVHV LQ 7DEOH.11 were controlled by the Dead Load + Floor Live Load FDVH DV VKRZQ LQ WKH H[DPSOH EHORZ LOAD COMBINATIONS: Per ASCE 7-10, the following load combinations were FRQVLGHUHG IRU WKLV H[DPSOH VQRZ ORDG 1. Dead + Floor Live Example: Given - Loadbearing wall supporting Roof, Ceiling, & &OHDU 6SDQ )ORRUV EXLOGLQJ ZLGWK RYHUKDQJV [ studs, 1" o.c., 0 psf roof dead load, 30 psf ground snow ORDG SOI ZDOO GHDG ORDG DQG D SVI ÀRRU OLYH ORDG. Dead + Snow 3. 'HDG )ORRU /LYH 6QRZ LOADS: 'HDG /RDGV Unbalanced Snow Load Dead Load wroof dead = 0 psf [(36 ft/) + ft] = 400 plf Ridge wwalldead = 11 psf (11 ft)( walls) = 4 plf wfloordead = 10 psf (36 ft/) ( floors) = 360 plf TOTAL = 1,00 plf 6QRZ /RDGV Left Side of Building %DODQFHG 6QRZ /RDG Floor Dead and Live Loads qsnow = 0.7CeCtIpg = 0.7(1.0)(1.1)(1.0)(30 psf) = 3.1 psf Floor Dead and Live Loads Header Rright(Snow) = = Exterior Wall 3.1 psf (36ft + ft + ft)/ 46 plf 8QEDODQFHG 6QRZ /RDG qsnow = Ipg (building width < 40 ft) = (1.0)(30 psf) = 30.0 psf Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 7
ENGINEERED DESIGN WFCM Commentary )RU EXLOGLQJ ZLGWKV JUHDWHU WKDQ IW L H IW ZLGWKV in Table.11), a more complex unbalanced snow loadlqj LV UHTXLUHG SHU ASCE 7-10 which places 30 percent of the balanced snow load on the windward side of the roof and 100 percent of the balanced snow load plus a rectangular surcharge snow load on the leeward side of WKH URRI 7KLV VXUFKDUJH ORDG VSDQV KRUL]RQWDOO\ IURP WKH ULGJH WR D GLVWDQFH HTXDO WR KdS(1/) where hd is the roof step drift height and S is the slope expressed as the roof UXQ IRU D ULVH RI RQH L H IRU D RQ VORSH 6 7KH PDJQLWXGH RI WKLV VXUFKDUJH VQRZ ORDG LV HTXDO to hdj S(1/) where J is the unit weight of snow, which is a function of the ground snow load, J pg SFI The slope, S, assumed in calculating the unit header loads IRU EXLOGLQJ ZLGWKV HTXDO WR IW LQ 7DEOH ZDV WDNHQ WR FRQVHUYDWLYHO\ PD[LPL]H WKH UHVXOWLQJ XQEDODQFHG VQRZ ORDG RQ WKH KHDGHU IRU HDFK EXLOGLQJ FRQ JXUDWLRQ )ORRU /LYH /RDGV wlive = 40 psf (36 ft/)( floors) = 1,440 plf 6XPPDUL]LQJ WKH ORDGV wdead = 1,00 plf wfloorlive = 1,440 plf wsnow = 467 plf (YDOXDWLQJ WKH ORDG FRPELQDWLRQV Dead + Floor Live = 1,00 + 1,440 =,44 plf Dead + Snow = 1,00 + 467 Sum moments about the top of the wall opposite the unbalanced roof snow load. = 1,469 plf 'HDG )ORRU /LYH 6QRZ = 1,00 + 0.75(1,440) + 0.75(467) Mleft = 0 =,43 plf Mleft = [(30.0 psf)(8)][(36 ft/) + ] - 36RRight Rright(Snow) = 467 plf Unbalanced Case Governs In accordance with ASCE 7-10, balanced and unbalanced VQRZ ORDGV DUH FKHFNHG DQG WKH ODUJHU XVHG LQ WKH FDOFXlation. Unbalanced snow loads are 1.3 (30.0/3.1) times larger than balanced snow loads, but only act along one KDOI RI D GXDO SLWFKHG URRI IRU UDIWHUV RU OHVV LQ VSDQ KRUL]RQWDO SURMHFWHG OHQJWK 7KHUHIRUH IRU IRUFHV DORQJ the exterior, unbalanced snow loads result in the maximum force to the wall. wtotal =,44 plf (WFCM Table.11) Tabulated values in Table.11 denoted with a * are inwhqghg WR PDNH WKH GHVLJQHU DZDUH WKDW WKHVH DUH JRYHUQHG by the Dead Load plus Floor Live Load combination. The designer should therefore apply the appropriate load duration factor, CD, of 1.0 when using these loads to design a wood header. http://awc.org/pdf/codes-standards/publications/archives/awc-asce7-05-snowprovisions-0607.pdf Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 8
Poll Question True or False: Studs should be checked for either MWFRS or C&C wind loads, but not both. 9
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM PRESCRIPTIVE DESIGN 3 3.1 General Provisions 115 3. Connections 116 3.3 Floor Systems 119 3.4 Wall Systems 11 3.5 Roof Systems 13 List of Figures 15 List of Tables 146 Appendix A 303 Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 30
PRESCRIPTIVE DESIGN 015 WFCM Table 3 Prescriptive Design Limitations Attribute Building Reference Section Figures 33' 3 80'.1.3.1 1.1.3.1a 1.1.3.1b 1. 6' 4" o.c. 3.1.3.a 3.1.3.b d 3.1.3.c.1a 3.1.3.d 3.1.3.e 3.1.3.f 3.1.3.g.1d.1i.1k 3.1.3.3a 3.1.3.3a 3.1.3.3b 3.1.3.3c.1, 3.1b Limitation BUILDING DIMENSIONS Mean Roof Height (MRH) Number of Stories Building Length and Width FLOOR SYSTEMS Lumber Joists Joist Span Joist Spacing Cantilevers Supporting loadbearing walls1 1 Floor Diaphragm Setbacks Loadbearing walls Vertical Floor Offset Floor Diaphragm Aspect Ratio Floor Diaphragm Openings Wall Studs Loadbearing Wall Height NonLoadbearing Wall Height Wall Stud Spacing Shear Walls Shear Wall Line Offset1 d df Tables 3.16B and 3.16C Lesser of 1' or 50% of Building Dimension WALL SYSTEMS 10' 0' 4" o.c. 4' Shear Wall Story Offset1 Shear Wall Segment Aspect Ratio Lumber Rafters No offset unless per Exception Table 3.17D ROOF SYSTEMS Rafter Span (Horizontal Projection) Rafter Spacing Eave Overhang Length1 Rake Overhang Length1 Roof Slope Roof Roof Diaphragm Aspect Ratio1 Diaphragms 1 See exceptions. For roof snow loads, tabulated spans are limited to 0 ft. 3.1.3.3d 3.1.3.3e 6' 4" o.c. 3.1.3.4a 3.1.3.4b Lesser of ' or rafter span/3 Lesser of ' or purlin span/ Flat 1:1 Tables 3.16A and 3.16C 3.1.3.4c 3.1.3.4c 3.1.3.4d 3.1.3.4e.1f.1g Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 31
WOOD FRAME CONSTRUCTION MANUAL 015 WFCM 3.3.4 Floor Sheathing 3.3.5 Floor Diaphragm Bracing 3.3.4.1 Sheathing Spans For 700-year return period, 3-second gust wind speeds greater than 130 mph, blocking and connections shall be provided at panel edges perpendicular to floor framing members in the first two bays of framing and shall be spaced at a maximum of 4 feet on center. Nailing requirements are given in Table 3.1 (see Figure 3.7b). Floor sheathing spans shall not exceed the provisions of Table 3.14. 3.3.4. Sheathing Edge Support 3 PRESCRIPTIVE DESIGN Edges of floor sheathing shall have approved tongue and groove joints or shall be supported with blocking, unless ¼ inch minimum thickness underlayment or 1½ inches of approved cellular or lightweight concrete is installed, or unless the finish floor is of ¾ inch wood strip. 3.4 Wall Systems 3.4.1 Exterior Walls 3.4.1.1 Wood Studs Wall studs shall be in accordance with the maximum spans for common species and grades of walls studs specified in Tables 3.0A-B and spaced in accordance with Table 3.0C. Exterior loadbearing studs shall be limited to a height of 10 feet or less between horizontal supports as specified in Table 3.0C. Exterior non-loadbearing studs shall be limited to a height of 14 feet or less for x4 studs and 0 feet or less for x6 and x8 studs in accordance with Table 3.0C. 3.4.1.1.1 Notching and Boring Notches in either edge of studs shall not be located in the middle one third of the stud length. Notches in the outer thirds of the stud length shall not exceed 5% of the actual stud depth. Bored holes shall not exceed 40% of the actual stud depth and the edge of the hole shall not be closer than 5/8 inch to the edge of the stud (see Figure 3.3b). Notches and holes shall not occur in the same cross section. EXCEPTION: Bored holes shall not exceed 60% of the actual stud depth when studs are doubled. 3.4.1.1. Stud Continuity Studs shall be continuous between horizontal supports, including but not limited to: girders, floor diaphragm assemblies, ceiling diaphragm assemblies, and roof diaphragm assemblies. When attic floor diaphragm or ceiling diaphragm assemblies are used to brace gable endwalls, the sheathing and fasteners shall be as specified in Table 3.15. The framing and connections shall be capable of transferring the loads into the ceiling or attic floor diaphragm (see Figures 3.7a-b). 3.4.1.1.3 Corners A minimum of three studs shall be provided at each corner of an exterior wall (see Figures 3.8a b). EXCEPTION: Reduced stud requirements shall be permitted provided shear walls are not continuous to corners. Framing must be capable of transferring axial tension and compression loads from above and providing adequate backing for the attachment of sheathing and cladding materials. 3.4.1. Top Plates Double top plates shall be provided at the top of all exterior stud walls. The double plates shall overlap at corners and at intersections with other exterior or interior loadbearing walls (see Figure 3.8d). Double top plates shall be lap spliced with end joints offset in accordance with the minimum requirements given in Table 3.1. 3.4.1.3 Bottom Plates Bottom plates shall not be less than inch nominal thickness and not less than the width of the wall studs. Studs shall have full bearing on the bottom plate. 3.4.1.4 Wall Openings Headers shall be provided over all exterior wall openings. Headers shall be supported by wall studs, jack studs, hangers, or framing anchors (see Figures 3.9a b). 3.4.1.4.1 Headers Maximum spans for common species of lumber headers and structural glued laminated timber beams used in exterior loadbearing walls shall not exceed the lesser of the applicable spans given in Tables 3.A E and Table 3.3A. Maximum spans for common species of lumber headers used in exterior non loadbearing walls shall not exceed spans given in Table 3.3B. 3.4.1.4. Full Height Studs Full height studs shall meet the same requirements as exterior wall studs selected in 3.4.1.1 (see Figures 3.9a b). The minimum number of full height studs at each end of the header shall not be less Copyright American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized. AMERICAN WOOD COUNCIL 3
WFCM Wood Frame Construction Manual for One- and Two-Family Dwellings 015 EDITION WORKBOOK Design of Wood Frame Buildings for High Wind, Snow, and Seismic Loads 33
General Information BUILDING DESCRIPTION WFCM Workbook Figure 1: Isometric view (roof overhangs not shown). 34 AMERICAN WOOD COUNCIL
015 Wood Frame Construction Manual Workbook BUILDING DESCRIPTION WFCM Workbook North Wall Heights Finished Grade to Foundation Top Floor Assembly Height Roof Pitch House Mean Roof Height Roof Overhangs Building Length (L) Building Width (W) Top plate to ridge height = 9' = 1' = 1' = 7:1 = 4.7' = ' = 40' = 3' = 9.3' Windows Typical 3'x4'-6" Foyer 6'x4'-6" Kitchen 4'x4'-6" Bath 4'x6' Doors Typical 3'x7'-6" Foyer 6'x7'-6" Kitchen 9'x7'-6" AMERICAN WOOD COUNCIL 35
General Information WFCM Workbook LOADS ON THE BUILDING Structural systems in the WFCM 015Edition have been sized using dead, live, snow, seismic and wind loads in accordance with ASCE/SEI 7-10 Minimum Design Loads for Buildings and Other Structures. Lateral Loads: Wind: 3-second gust wind speed in Exposure Category B (700 yr. return) = 160 mph Seismic: Simplified Procedure (ASCE 7-10 Section 1.14) Seismic Design Category (SDC) (ASCE 7-10 Section 11.4. and IRC Subcategory) = D1 Vertical force distribution factor (F) - (ASCE 7-10 Section 1.14.8.1) = 1. Gravity Loads*: Roof: Roof Dead Load Ground Snow Load, Pg Roof Live Load = = = 10 psf 30 psf 0 psf Ceiling: Roof Ceiling Load = 10 psf *Assumptions vary for wind and seismic dead loads Floors: First Floor Live Load Second Floor Live Load Attic Floor Live Load Floor Dead Load = = = = 40 psf 30 psf 30 psf 10 psf Walls: Wall Dead Load = 11 psf Deflection limits per 015 IRC Roof Rafters with flexible Ceiling Attached Roof Rafters with no Ceiling Attached Raised Ceiling Joists with flexible finish Floor Joists Exterior Studs (gypsum interior) L/Δ = L/Δ = L/Δ = L/Δ = H/Δ = 40 180 40 360 180 Note: See comparable deflection limits in 015 IBC section 308 for joists and rafters. 015 International Residential Code for One- and Two-Family Dwellings, International Code Council, Inc., Washington, DC. Reproduced with permission. All rights reserved. www.iccsafe.org AMERICAN WOOD COUNCIL 36