Wood Connections
Sam Hensen, P.E.Branch Engineering Manager
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Must provide sufficient capacity to transfer loads to supporting membersUtilize fastener spacing which does not cause splitting of the lumberHold the wood members in a manner such that shrinkage/swelling cycles do not induce splitting across the grainMinimize regions that might collect moistureMinimize the potential for tension perpendicular to grain stressesChoose a finish on the connector appropriate for the application
Concepts of Well Designed Connections
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ProductionWill 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?
Concepts of Well Designed Connections
Alternative Materials
IBC 104.11 Alternative Materials, design and methods of construction and equipmentThe 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 ReportsSupporting 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
Lab performs
test
Independent Agency
Witnesses Test
IndependentAgency
issues Lab report
Lab report & Calculations submitted to Evaluation
AgencyEvaluation
Agency issues Code
Report
Approval process
Lab does test
Lab issues Report
Evaluation Agency establishes
minimum QA and QC requirements
Evaluation Agency
Performs biannual audits
Acceptance Criteria Established through consensus process
Building Official Confident in
product evaluation
IAPMO-ES
Accredited by the American National Standards Institute (ANSI)Began evaluating plumbing and mechanical productsApproved to evaluate structural productsIAPMO-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 complianceMade 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 codesAn evaluation report is not to be construed as representing a judgment about aesthetics or any other attributes not specifically addressed in the reportNot an endorsement or recommendation for use of the subject of the reportApproval 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 actuallyoperating 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 completedThe qualifying inspection will verify that the manufactured products are consistent with the recognized evaluation reportThe 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
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The Process of Selecting the Appropriate Connector
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What is the application?
CONCRETE ANCHORS POST BASES POST CAPS FACE MOUNT HANGERS
TOP FLANGE HANGERS
PLATED TRUSS MASONRY STRAPS AND TIES
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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
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How are the members oriented relative to one another?
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What are the type of Fasteners that will be used?
SDS SCREWSBOLTS NAILS
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What is the Load Requirement for the Connection?
Gravity Load (LL, SL, RL, WL)?
Uplift Load?
Lateral Load?
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What are the costs?
Website
http://www.strongtie.com/literature/pricebook/
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What is the appropriate finish for the connector (if applicable)?
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Finishes Available
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Concerns with PTW
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IBC - Fasteners
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IRC - Fasteners
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Technical Assistance Available!
1-800-999-5099
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Where did all of these products come from?
Building Code Driven
Specifier Driven
Installer Driven
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BUILDING CODES
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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 corrosion-resistant material not less than 0.040-inch nominal thickness (20 ga)
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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.
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How do we determine the
allowable loads?
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IBC 2304.9.3Joist 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
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Connector Allowable Load Determination
Lowest Value from 3 Tests of either 1/8Deflection Limit or
Ultimate/3 Limit
Code Allowed Fastener and Bearing
Calculations
Steel Capacity (strap type products)
IBC 1716.1Requires that the connector allowable load be determined from the lowest of the following
Building CodeRequirements
Lumber Capacity
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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
Bolt Yield Limit Equations
Single vs Double Shear
Edge/End distances
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Determining NDS Fastener Calculation Limitations
CAPACITY OF A SINGLE NAIL IS A FUNCTION OF:
0 1 ½ 3 3¼ 3½
1. Nail Diameter
2. Nail Length in member
3. Nail bending yield strength
4. Lumber S.G.
5. Steel Thickness
6. Steel Tensile Strength
10dX1½
8dX1½
10d Common
16d Sinker
16d Common
0.162
0.148
0.148
0.148
0.131
10.2.3 Design of Metal Parts
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Up
lift
Do
wn
loa
d
Continuous Load Path
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Examine an HTU210
HTU210Max Nailing Requires
32-16d Common Nails
Allowable Floor Load = 4705 lbs
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Nail capacity calc from the NDS
32 Nails x 147 lbs = 4705 lbs
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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
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Load Duration Factors
ApplicationDuration Factor
Duration Assumption
Floor Load (D+L)
1.0 10 Years
Snow Load 1.15 3 Months
Roof Live Load
1.25 7 Days
Wind/EQ Load
1.60 10 Minutes
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Nail Limitations
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
32 Nails X 127 = 4705 lbs (100)
Calculated Nail Values
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Why Test if Calcs show it works?
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Determining Test Limitations
Test #1
1/8 Ult/3
Test #2
1/8 Ult/3
Test #3
1/8 Ult/3
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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
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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)
Nail Limitations
Test Limitation on HU210 = 5995 lbs (Steel tore at 17985 lbs)
Test Limitation
5995 lbs
5760 lbs *
5345 lbs *
* ANSI/TPI limitations on truss chords limit listed values Reference T-ANSITPI technical bulletins
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Simpson Test Labs
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Simpson Connector Test Lab
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Code Bearing Requirements
IRC R502.6 BearingThe 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
IBC 2308.8.1 BearingExcept 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.
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What is a Ribbon Strip?
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1 2
3 4
1½ of bearing?
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Straps and angles are not hangers!
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Solid Sawn LumberSolid Sawn Lumber
Plated TrussPlated Plated TrussTruss
Composite Wood I -joist
Composite Composite Wood Wood II --joistjoist
Structural Composite
Lumber
Structural Structural CompositeComposite
LumberLumber
HANGERS
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HANGER TYPES
FACE MOUNTTOP FLANGESLOPED & SKEWEDOPTIONSSPEC NON-CATALOGCUSTOMS
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Nail Hole Identification
Fill all round holes
Triangle holes optional for additional load
Diamond holes optional for ease of installation
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Round Nail HolesRound Nail Holes
Fill all round and obround nail holes Exception to the rule: Strap hangers and straps
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General Installation of Connectors
Manufacturers face the facts:Proper nails are not always usedSimpson provides tables that have factors for use of some alternate size nailsAlso reduction for inadequate nail penetration (10 nail diameters):1-3/8 for 8d1-1/2 for 10d1-5/8 for 16dDepth of connected members important (e.g. reduction for 3-inch nail in 2x member)
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Alternate Nails
Can NOT substitute 1½ nails in double shear hangersLUS, MUS, HUS, HHUS, HGUS
Top Flange Hangers, hurricane ties and any others not applicable to this table
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Prevent Torsional Effects
IBC 1715.1.3 requires torsion to be factored into the capacity of a hanger or provide restraint against torsion
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Header Nails should find lumber or a reduction in capacity must be calculated.
Hanger Height Considerations
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Joist or truss should not be more than 1/8 from the Header
Too much gap
Short Cut Joist or Trusses
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Hanger not Plumb
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Hanger Over Spread
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Field Bent Flanges
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Field Welded
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4-1 segments for < 3280 lbs
6-1 segments for 3280 lbs to 4855 lbs
Don t recommend welding thicknesses less than 14 Ga.
Welded Applications
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What are we Connecting To?
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HU Hangers to Block/Concrete Walls
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CONNECTOR SELECTOR
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Up
lift
Lateral
Continuous Load Path
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Overall Wind Effects
Roof suction (uplift)
Suction on side and back walls
Positive (inward) pressure on windward walls
Flow patternPressure distribution
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1) Sheathing
2) Truss/Rafter to Top Plate
3) Top Plate to Stud
4) Header to Studs
5) Stud to Stud
6) Stud to Sill Plate
7) Sill Plate to Foundation
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5
6
Uplift Load Path
1
7
4
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Has Anyone Seen My Roof?
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Truss to Wall Connections
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Girder to Wall Connections
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Remember the Contractor!
Every other truss and stud will line up!
Don t end up with this!
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When Framing Aligns
H10STruss to studAllows for offsetWorks for masonry
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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
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Top Plate to Wall Connectors
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Headers to Studs
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Floor to Floor Connectors
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Stud to Sill Plate
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Sill Plate to Foundation
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MAS Installed
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MAS Installed
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Lateral
Continuous Load PathD
ow
nlo
ad
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Ceiling Joists an Rafter Connections Continuous Tie Across Building
Ceiling joist tie prevents walls from spreading under downward load on rafters
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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).
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Table R802.5.1.9
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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 toceiling 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.
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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.
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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
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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
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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.
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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.
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What s the issue here?
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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
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Rafter Tie
Lookout nailed to rafter
Strap connects lookout to joists
Subflooring connects joists across floor
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1x4 Crosstie Location1x4 Crosstie Location
Have to adjust span based on height of joist or tie (see Span Tables)
2x4
2x42x4
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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.
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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
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Lateral
Continuous Load Path
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Shearwall Overturning Restraint
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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
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QUESTIONS?