Wood Connections Sam Hensen, P.E. Branch Engineering Manager Concepts of Well Designed Connections Must provide sufficient capacity to transfer loads to supporting members Utilize fastener spacing which does not cause splitting of the lumber Hold the wood members in a manner such that shrinkage/swelling cycles do not induce splitting across the grain Minimize regions that might collect moisture Minimize the potential for tension perpendicular to grain stresses Choose a finish on the connector appropriate for the application 2 Concepts of Well Designed Connections Production Will the last part look like the first part? Will the part be the same in San Antonio and Dallas, Florida, Virginia? Accuracy of rated loads To what standard? What does approved sources mean for alternate products not listed in the building code? 3
Alternative Materials IBC 104.11 Alternative Materials, design and methods of construction and equipment The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability and safety. Alternative Materials IBC 104.11.1 Research Reports Supporting data, where necessary to assist in the approval of materials or assemblies not specifically provided for in this code, shall consist of valid research reports from approved sources. ICC-ES and IAPMO-ES Approval process Acceptance Criteria Established through consensus process Evaluation Agency establishes minimum QA and QC requirements Lab performs test Evaluation Agency issues Code Report Independent Agency Witnesses Test Evaluation Agency Performs biannual audits Independent Agency issues Lab report Building Official Confident in product evaluation Lab report & Calculations submitted to Evaluation Agency Lab does test Lab issues Report
IAPMO-ES Accredited by the American National Standards Institute (ANSI) Began evaluating plumbing and mechanical products Approved to evaluate structural products IAPMO-ES performs technical evaluations of building products, components, methods, and materials. Issues reports on code compliance Made available free of charge to code officials, contractors, specifiers, architects, engineers, and anyone else with an interest in the building industry and construction. IAPMO-ES evaluation reports provide evidence that products and systems meet code requirements. ICC-ES ICC-ES is a nonprofit, public-benefit corporation. (Not ICC) ICC-ES performs technical evaluations of building products, components, methods, and materials. Issues reports on code compliance Made available free of charge to code officials, contractors, specifiers, architects, engineers, and anyone else with an interest in the building industry and construction. ICC-ES evaluation reports provide evidence that products and systems meet code requirements. ICC-ES/IAPMO-ES Main purpose evaluation reports is to assist those enforcing model codes to determine whether a given subject complies with those codes An evaluation report is not to be construed as representing a judgment about aesthetics or any other attributes not specifically addressed in the report Not an endorsement or recommendation for use of the subject of the report Approval for use of the subject of the report is the prerogative and responsibility of the Code Official
ICC-ES Quality Assurance Applicants for ICC-ES evaluation reports are required to provide quality documentation for the products to be covered in the report At the time of the qualifying inspection, the inspector will check the completeness of the documentation The inspector will also verify that the manufacturer is actually operating in accordance with the quality documentation, and that the product being manufactured is consistent with the product information submitted to ICC-ES. For cases where the report holder and the manufacturer are different, and the manufacturer is not an additional listee on the report, the report holder and the manufacturer will have to jointly fill out and submit ICC-ES Quality Assurance Prior to publication of a new ICC-ES evaluation report ICC-ES must have objective evidence that a qualifying inspection of the facilities manufacturing products to be recognized in the evaluation report has been successfully completed The qualifying inspection will verify that the manufactured products are consistent with the recognized evaluation report The manufacturer has documented and effectively implemented a quality system that meets all requirements of ICC-ES Agencies must be accredited for inspections of the product in question ICC-ES Quality Assurance
IAPMO-ES Quality Assurance IAPMO-ES Quality Assurance The Process of Selecting the Appropriate Connector 15
What is the application? CONCRETE TOP FLANGE HANGERS ANCHORS PLATED TRUSS POST BASES FACE MOUNT HANGERS POST CAPS MASONRY STRAPS AND TIES 16 What are the Size and Species of the Members? Dimension Lumber Sizes (2X4, 2X6, etc ) Engineered Wood Sizes (Glulam, LVL, I-joist, etc ) Member Species (DF, SP, SPF, HF) Fastened to Steel, Concrete, or Block 17 How are the members oriented relative to one another? 18
What are the type of Fasteners that will be used? BOLTS NAILS SDS SCREWS 19 What is the Load Requirement for the Connection? Gravity Load (LL, SL, RL, WL)? Uplift Load? Lateral Load? 20 What are the costs? Website http://www.strongtie.com/literature/pricebook/ 21
What is the appropriate finish for the connector (if applicable)? 22 Finishes Available 23 Concerns with PTW 24
IBC - Fasteners 25 IRC - Fasteners 26 Technical Assistance Available! 1-800-999-5099 27
Where did all of these products come from? Building Code Driven Specifier Driven Installer Driven 28 BUILDING CODES 29 Load Path Requirements IBC Section 2304.9.6 Where wall framing members are not continuous from foundation sill to roof, the members shall be secured to ensure a continuous load path. Where required, sheet metal clamps, ties or clips shall be formed of galvanized steel or other approved corrosionresistant material not less than 0.040- inch nominal thickness (20 ga) 30
Load Path Code Requirement IBC Section 1604.4 Analysis Any system or method of construction to be used shall be based on a rational analysis in accordance with well-established principles of mechanics. Such analysis shall result in a system that provides a complete load path capable of transferring loads from their point of origin to the load-resisting elements. Every structure shall be designed to resist the overturning effects caused by the lateral forces specified in this chapter. 31 How do we determine the allowable loads? 32 IBC 2304.9.3 Joist hangers and framing anchors Connections depending on joist hangers or framing anchors, ties and other mechanical fastenings not otherwise covered not otherwise covered are permitted where approved. The vertical loadbearing capacity, torsional moment capacity, and deflection characteristics of joist hangers shall be determined in accordance with Section 1716.1 33
Connector Allowable Load Determination Building Code Requirements IBC 1716.1 Requires that the connector allowable load be determined from the lowest of the following Code Allowed Fastener and Bearing Calculations Lowest Value from 3 Tests of either 1/8 Deflection Limit or Ultimate/3 Limit Steel Capacity (strap type products) Lumber Capacity 34 Determining NDS BOLT Calculation Limitations CAPACITY OF A BOLT IN LUMBER IS A FUNCTION OF: 1. Bolt Diameter/length in members 2. Lumber S.G. 3. Fastener Grouping 4. Edge/End distances 5. Orientation of load to lumber grain 6. Number of members being attached 7. Duration of Load 8. Steel Strength when connecting metal to wood 35 Bolt Yield Limit Equations
Single vs Double Shear Edge/End distances Determining NDS Fastener Calculation Limitations CAPACITY OF A SINGLE NAIL IS A FUNCTION OF: 1. Nail Diameter 2. Nail Length in member 3. Nail bending yield strength 4. Lumber S.G. 5. Steel Thickness 6. Steel Tensile Strength 8dX1½ 10dX1½ 10d Common 16d Sinker 16d Common 0.131 0.148 0 1 ½ 3 3¼ 3½ 0.148 0.148 0.162 39
10.2.3 Design of Metal Parts Continuous Load Path Dow Uplift nload 41 Examine an HTU210 HTU210 Max Nailing Requires 32-16d Common Nails Allowable Floor Load = 4705 lbs 42
Nail capacity calc from the NDS 32 Nails x 147 lbs = 4705 lbs 43 Load Duration Concept Nail calculations are at a normal load duration What is a normal Load Duration? Weight Time Holding 5 lbs 120 seconds 20 lbs 30 seconds 50 lbs 10 seconds 100 lbs 2 seconds 44 Load Duration Factors Application Duration Factor Duration Assumption Floor Load (D+L) 1.0 10 Years Snow Load 1.15 3 Months Roof Live Load Wind/EQ Load 1.25 7 Days 1.60 10 Minutes 45
Nail Limitations Calculated Nail Values 32 Nails X 127 = 4705 lbs (100) Floor: 1.00 X 4705 = 4705 lbs (100) Snow: 1.15 X 4705 = 5411 lbs (115) Roof: 1.25 X 4705 = 5881 lbs (125) Wind: 1.60 X 4705 = 7528 lbs (160) Each Value is compared against test limitations 46 Why Test if Calcs show it works? 47 Determining Test Limitations Test #1 Test #2 Test #3 1/8 Ult/3 1/8 Ult/3 1/8 Ult/3 48
What s the Factor of Safety? Item Factor of Safety Connectors (except straight straps) 3.0 Straight Strap Connectors Per steel design manuals Shear Walls 2.0 Anchor Systems Products 4.0 49 Nail Limitations Test Limitation Test Limitation on HU210 = 5995 lbs (Steel tore at 17985 lbs) Floor: 1.00 X 4705 = 4705 lbs (100) Snow: 1.15 X 4705 = 5411 lbs (115) 5345 lbs * Roof: 1.25 X 4705 = 5881 lbs (125) 5760 lbs * Wind: 1.60 X 4705 = 7528 lbs (160) 5995 lbs * ANSI/TPI limitations on truss chords limit listed values Reference T-ANSITPI technical bulletins 50 Simpson Test Labs 51
Simpson Connector Test Lab 52 Code Bearing Requirements IBC 2308.8.1 Bearing Except where supported on a 1 by 4 ribbon strip and nailed to the adjoining stud, the ends of each joist shall not have less than 1 1/2 of bearing on wood or metal, or less than 3 on masonry. IRC R502.6 Bearing The ends of each joist, beam or girder shall have not less than 1.5 of bearing on wood or metal and not less than 3 on masonry or concrete except where supported on a 1 by 4 ribbon strip and nailed to the adjacent stud or by the use of approved joist hangers 53 What is a Ribbon Strip? 54
55 1 2 1½ of bearing? 3 456 57
58 Straps and angles are not hangers! 59 Solid Sawn Lumber Composite Wood I-joist HANGERS Structural Composite Lumber Plated Truss 60
HANGER TYPES FACE MOUNT TOP FLANGE SLOPED & SKEWED OPTIONS SPEC NON-CATALOG CUSTOMS 61 Nail Hole Identification Fill all round holes Triangle holes optional for additional load Diamond holes optional for ease of installation 62 Round Nail Holes Fill all round and obround nail holes Exception to the rule: Strap hangers and straps 63
General Installation of Connectors Manufacturers face the facts: Proper nails are not always used Simpson provides tables that have factors for use of some alternate size nails Also reduction for inadequate nail penetration (10 nail diameters): 1-3/8 for 8d 1-1/2 for 10d 1-5/8 for 16d Depth of connected members important (e.g. reduction for 3-inch nail in 2x member) 64 Alternate Nails Can NOT substitute 1½ nails in double shear hangers LUS, MUS, HUS, HHUS, HGUS Top Flange Hangers, hurricane ties and any others not applicable to this table 65 Prevent Torsional Effects IBC 1715.1.3 requires torsion to be factored into the capacity of a hanger or provide restraint against torsion 66
67 Hanger Height Considerations Header Nails should find lumber or a reduction in capacity must be calculated. 68 Short Cut Joist or Trusses Joist or truss should not be more than 1/8 from the Header Too much gap 69
Hanger not Plumb 70 Hanger Over Spread 71 Field Bent Flanges 72
Field Welded 73 Welded Applications 4-1 segments for < 3280 lbs 6-1 segments for 3280 lbs to 4855 lbs Don t recommend welding thicknesses less than 14 Ga. 74 What are we Connecting To? 75
76 HU Hangers to Block/Concrete Walls 77 CONNECTOR SELECTOR 78
Uplift Continuous Load Path Lateral 79 Overall Wind Effects Roof suction (uplift) Suction on side and back walls Positive (inward) pressure on windward walls Pressure distribution Flow pattern 80 Uplift Load Path 1 1) Sheathing 2) Truss/Rafter to Top Plate 2 3 4 3) Top Plate to Stud 4) Header to Studs 5 5) Stud to Stud 6) Stud to Sill Plate 6 7 7) Sill Plate to Foundation 81
Has Anyone Seen My Roof? 82 83 Truss to Wall Connections 84
Girder to Wall Connections 85 Remember the Contractor! Every other truss and stud will line up! Don t end up with this! 86 When Framing Aligns H10S Truss to stud Allows for offset Works for masonry 87
Overlapping Connectors 24 & 16 O.C. Every other truss/rafter will line up with a stud 2 options: Tie truss/rafter directly to stud Use alternate connectors Remember the H10S 88 89 Top Plate to Wall Connectors 90
Headers to Studs 91 92 Floor to Floor Connectors 93
94 Stud to Sill Plate 95 96
Sill Plate to Foundation 97 MAS Installed 98 MAS Installed 99
Continuous Load Path Dow nload Lateral 100 Ceiling Joists an Rafter Connections Continuous Tie Across Building Ceiling joist tie prevents walls from spreading under downward load on rafters 101 R802.3.1 Ceiling joist and rafter connections Ceiling joists and rafters shall be nailed to each other in accordance with Table R802.5.1(9), and the rafter shall be nailed to the top wall plate in accordance with Table R602.3(1). 102
Table R802.5.1.9 103 Table R802.5.1.9 Footnotes a. 40d box nails shall be permitted to be substituted for 16d common nails. b. Nailing requirements shall be permitted to be reduced 25 percent if nails are clinched. c. Heel joint connections are not required when the ridge is supported by a load-bearing wall, header or ridge beam. d. When intermediate support of the rafter is provided by vertical struts or purlins to a load bearing wall, the tabulated heel joint connection requirements shall be permitted to be reduced proportionally to the reduction in span. e. Equivalent nailing patterns are required for ceiling joist to ceiling joist lap splices. f. When rafter ties are substituted for ceiling joists, the heel joint connection requirement shall be taken as the tabulated heel joint connection requirement for two-thirds of the actual rafter-slope. 104 Table R802.5.1.9 Footnotes g. Tabulated heel joint connection requirements assume that ceiling joists or rafter ties are located at the bottom of the attic space. When ceiling joists or rafter ties are located higher in the attic, heel joint connection requirements shall be increased by the following factors: where: Hc = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls. HR = Height of roof ridge measured vertically above the top of the rafter support walls. 105
R802.3.1 Ceiling joist and rafter connections Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters 106 R802.3.1 Ceiling joist and rafter connections Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters 107 R802.3.1 Ceiling joist and rafter connections (continued) Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the attic shall be installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. 108
R802.3.1 Ceiling joist and rafter connections (continued) Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Rafter ties shall be a minimum of 2-inch by 4-inch (nominal), installed in accordance with the connection requirements in Table R802.5.1(9), or connections of equivalent capacities shall be provided. 109 What s the issue here? 110 Continuous tie examples Rafter ties used to be spaced not more than 4 feet o.c. NOW, have to space at 24 so you can meet fastening of Table 802.5.1.9 111
Rafter Tie Lookout nailed to rafter Strap connects lookout to joists Subflooring connects joists across floor 112 2x4 1x4 Crosstie Location 2x4 Have to adjust span based on height of joist or tie (see Span Tables) 113 Adjust rafter span for height of tie The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below: where: HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls. HR = Height of roof ridge measured vertically above the top of the rafter support walls. 114
R802.3.1 Ceiling joist and rafter connections (continued) Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice. Ridge beam must be supported 115 Continuous Load Path Lateral 116 Shearwall Overturning Restraint 117
Simpson Strongwall Shearwall Steel Strong-Wall Widths Available from 12 to 24 Plate Heights from 8 to 13 Stackable up to 20 plate height Ordinary Moment Frame Column Widths 6 to 15 Plate Heights from 8 to 19 Clear openings 8 to 16 118 QUESTIONS? 119