WOOD PRODUCTS COUNCIL WEBINAR February 18, 2011

Connection Solutions for  Wood Framed Structures Wood Framed Structures  Tom Williamson, P.E. Consulting Engineer Consulting Engineer Retired Vice President, APA

“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported t d to t AIA/CES for f AIA members. b Certificates C tifi t off Completion C l ti for f both AIA members and non-AIA members are available upon request. This program 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. Questions related to specific materials materials, methods methods, and services will be addressed at the conclusion of this presentation.

Learning Objectives Copyright Materials #1 To familiarize designers with the wide variety of connectors

This presentation is protected by US and International Copyright laws. Reproduction, di t ib ti distribution, di display l and d use off th the presentation t ti without written permission of the speaker is prohibited.

© The Wood Products Council 2010

available for wood framed structures and how they can be used most effectively to meet a specific design need. #2 To acquaint designers with how design properties are established for wood connectors and what adjustment factors must be applied to ensure the proper performance of these connectors. t #3 To provide design professionals with an overview of wood connection techniques to help ensure efficient, durable and structurally sound connections #4 To use design examples to illustrate these principles and to acquaint designers with additional resources available to assist them in wood connection design and detailing.

Outline •Fastener Fastener types •Fastener design values •Connection design basics Wood connection design •Wood philosophy •Environmental E i t l effects ff t - moisture i t p •Examples •Additional information

Mechanical Connectors

Nails are generally used when loads are light. They are used for light-frame construction, diaphragms, and shear walls. Staples can be used in place of nails, but equivalent capacities need to be confirmed

Screws may be more satisfactory than nails under vibration or ithdra al loads since the they ha have e withdrawal less tendency to work loose

Mechanical Connectors Common Dowel Type Fasteners  Nails  Staples  Wood Screws  Lag screws  Bolts B lt

Light Frame Commercial Buildings

Mechanical Connectors

Other types:  Timber rivets  Split rings  Shear plates  Metal plates  Wood dowels  Pre-engineered hangers

Specialized Connectors  Split Ring  Wood-to-wood  Require special tooling of wood prior to job site

 Shear Plates  Wood-to-wood or wood-to-dissimilar materials (concrete or steel)

 Both have successful long history  Glulam or PSL

 NDS provides design values

Timber Rivets  Timber Rivets  Hot-Dipped Galvanized  Fixed-shank cross-section  Fixed head dimension  Vary only in length  NDS provides design values  Used in Canada for several decades  Added to 2005 NDS  Glued Laminated Timber  DFL  SP

National Design Specification

 Long History > 100 years  Wood dowels and pegs  Difficult to obtain published design values  Uses automated CNC milling technology  Timber Framer’s Guild www.tfguild.org

Pre-Engineered Pre Engineered Connectors Joist and beam hangers  Top and face mount

 Product specific  Use correct nails  Fill all holes  Ensure proper fastener penetration

Air Force Trestle Project Wood bolts ((laminated beech)) in all-wood structure

150 feet

All-Wood All Wood Fasteners System

Pre-Engineered Pre Engineered Connectors

Pre-Engineered Hold-Downs All i ffor Sh Allowing Shrinkage i k

Pre-Engineered Pre Engineered Connectors Hold-down Hold down hardware

 Proprietary devices are a ailable to address potential available shrinkage problems in multi-story multi story buildings  Need to verify code compliance with manufacturer

Small Diameter Fasteners Lots of Types box box nail common nail ring shank ring sinker, cooler, …

Lots of Pennyweights 2d, 4d, 6d, 8d, 10d, …

Small Diameter Fasteners Nails and nomenclature       

Short Box nail Ri nail Ring il Common nail Sinker Power-driven Roofing

 Etc. Etc

Specifying Nails

Nail Nomenclature There is no control over nail nomenclature! Manufacturers can and will call fasteners anything y g that they y want. 10d is not a clear specification!

In ASTM F 1667 both pennyweight and type define a size Avoid problems by specifying pennyweight, t type, di diameter t and d length l th

 Ex: E 10d common : 0 0.148” 148” x 3”

Nail Comparison

Small Diameter Fasteners Nails and nomenclature        

Short Box nail Ring nail Common nail Sinker Power-driven Roofing Etc Etc.

C Comparison i off common, box b and d sinker i k nails il Type

Pennyweight

Length

Diameter

Box

10d

3”

.128

Sinker

10d

2‐7/8”

.120

Common

10d

3” 3

.148 148

Assume 1-1/2” side member thickness Diameter

Lateral Load  for DF

Common

Box

Sinker

.148

118 lbs

10d

20d

16d

Power Driven Nailed Connections Often Used in Shear Walls and Diaphragms

Power Driven Nailed Connections Of Often U Used d iin Sh Shear W Walls ll and d Di Diaphragms h

Nail installation

APA Prescriptive Recommendations for overdriven nails provided in APA Technical Topic TT-012A

Overdriving reduces performance

If < 20% fasteners overdriven by 20% fasteners overdriven by >1/8”, th add then dd 1 additional dditi l fastener f t for f every 2 overdriven. di Or:  re-analyze l capacity it based b d on average thickness thi k of panel measured from the bottom of the nail head  example: 5/8” panel with fasteners overdriven by 1/8” = capacity of 1/2” 1/2 panel  adjust nailing schedule accordingly

Large a ge Sc Screw ew Type ype Fasteners aste e s Lag Screws or Lag Bolts  Typically used as an alternative to bolts  Turned into prepre drilled holes  Lead holes are a function of sp. gr. of wood g

Bolted Connections Bolts  1/2”, 5/8”, 3/4”, 7/8”, 1” inch diameters  Diameters of >1” not permitted by the NDS since they can initiate high g tension-perp p p stresses on the bolt hole that can induce splitting of the wood  Pre-drilled holes 1/32” to 1/16” larger than diameter used  Common C mistake i t k iis nott allowing room for installation

Bolted Connections

Bolted Connections

Bolts may have more slip than others due to over drilled holes which other fasteners such as screws do not require Bolted Screw

Bolted Truss Connections

Align fasteners concentrically with forces – avoid eccentricities

Partially Concealed Kerf Plate B lt d C Bolted Connections ti

Long Span Arches with ith Moment M t Splice S li

Moment Splice

Lag screws

Bolts

Steel plates plus mechanical fasteners top/bottom transfer axial tension and compression forces pressure plates l t transfer t f thrust th t shear plates transfer shear

Design/Specification Options Prescriptive  Follows a recipe  IBC, IRC, ESR reports and tables  Based on predetermined design values, joint configuration, materials used, etc  Ex: IBC tables for shear walls or diaphragms

Engineered  NDS & NER-272  Published design values  Accounts for performance of different materials  Nominal values  Adjustments j applied pp for end use conditions

Chicago Bears Practice Facility

Engineered Connection Design Must evaluate and provide for:  forces present  environmental effects  material effects  aesthetics

Basic Theory: Engineered Design  Nominal design values al es determined based on equations provided in the NDS  Nominal design values published in tables in the NDS or in other references  Published nominal design values based on assumed end-use conditions  Normal load duration (10 year)  Dry condition of use  And others

Other References for Mechanical Fasteners ICC Reports p  NER-272 International Staple, Nail and Tool Association  ESR-1539 International Staple, N il and Nail d Tool T l Association ISANTA

Basic Theory: Engineered Design Values published for: Nails Wood Screws Lag Screws Bolts Shear Plates Split Rings Timber Rivets

Fastener Interchangeability ISANTA NER-272 or ESR-1539  Provide “conversion” conversion tables for prescriptive requirements For example, if model code requires 8d commons at 6” oc, then th what h t fastener f t type t and d spacing i is i “equivalent”

 Has values for engineered designs for staples and d a variety i t off other th power-driven di fasteners f t  Available from International Staple, Nail and Tool Association (ISANTA) www.isanta.org  NDS does not have design values for staples

Basic Theory: Engineered Design For dowel F d l type t fasteners: f t nails, il spikes, ik bolts, lag screws and wood screws  Lateral L t l load l d design d i values l are calculated l l t d by b yieldi ld limit equations – Yield Model  Withdrawal design capacity calculated from empirical (test-based) equations

Split p rings, g , shear plates, p , dowels,, drift pins, and timber rivets etc.  Lateral and withdrawal design g values from empirically based tables

Yield Equations (Based on Mode)

Lateral Connection Strength, Strength Z Lateral connection strength, Z, based on yield model and depends on:  Crushing (bearing) strength of wood  Size of wood pieces

Z

 Fastener size and strength  Plus applicable end use adjustment factors

NDS DOWEL YIELD EQUATIONS MODE I

Mechanics based: 4 modes 6 equations

bearing dominated yield y of wood fibers

MODE II pivoting of fastener with localized crushing of wood fibers

NDS DOWEL YIELD EQUATIONS MODE III fastener yield in bending at one plastic hinge and bearing dominated yield of wood fibers

MODE IV fastener yield in bending at two plastic hinges and bearing dominated yield of wood fibers

Withdrawal Connection Strength Withdrawal Connection Strength Depends On:  Depth of

penetration in main member

 Wood density  F Fastener t size i and d type  Plus applicable end use adjustment factors

Connection Design The NDS has design provisions and tabulated nominal values for commonly l used d connectors t for wood framed structures Allowable = nominal x adjustment factors Adjustment factors account for a wide range of different end use conditions

Typical Tabulated Results Nominal connection strengths are tabulated in pages of tables in the NDS and other reference books Thickness Steel Main G = 0.50 side Bolt member b plate ts , diameter D Douglas-Fir-Larch l Fi L h Z , lb Zll, lb tm , in D, in in 2 1/2 2-1/2 1/4 1/2 1510 790 5/8 2190 880 3/4 2630 980 7/8 3060 1050 1 3500 1130

G = 0.43 H Fi Hem-Fir Z , lb Zll, lb 1410 640 1880 700 2250 770 2630 830 3000 900

Yield Equation Input Parameters Specific Gravity

Equivalent Specific Gravity (G) f N for Nail il L Lateral t lV Values l iin LVL

For composite engineered wood products such as SCL (LVL, (LVL PSL, PSL LSL and OSL) use an equivalent specific gravity gravity, as determined by the manufacturer based on tests

Connections With Wood Structural Panels

Dowel Bearing Strength of W d St Wood Structural t lP Panell and dN Nails il Wood Structural Panel Plywood Structural I, ((a)) Other grades Oriented Strand All grades

Specific Gravity, G

Dowel Bearing Strength, Fe

0.5 0 42 0.42

4650 psi 3350 psi

0.5

4650 psi

(a) Use G = 0.42 when species of the plies is not known. When species

of the plies is known, specific gravity listed for the actual species and the corresponding p g dowel bearing g strength g mayy be used,, or the weighted g average may be used for mixed species.

Angle to Grain Adjustments H ki Hankinson Formula F l

Adjustment Factors

Geometry Factor, Factor CΔ Minimum Spacing, End, & Edge Distances Parallel and perpendicular to grain When D < ¼”, C∆ = 1.0 When D > ¼” and if end distance OR spacing p g < required q then C∆ factor applied to all fasteners

Calculate wood bearing strength, strength Fe, at any angle to grain (for large fasteners: bolts, lag screws, etc) Not necessary for nails or wood screws



Fe  Fe

Fe Fe  Fe sin 2   Fe  cos 2 

Fe Fell

Multiple-Bolt Multiple Bolt Tension Connection Determine the adjusted ASD capacity of the multiple-bolt double shear tension connection ti att the th end d off the th 24F-V4 24F V4 D Douglas-Fir l Fi glulam l l Given: (2) ¼” thick A36 steel side plates (6) 1” 1 Φ A307 bolts Seismic Tension Load

2 steel pl’s  (1/4”x6”)

5 1/8 x 12 GLB GLB dry (initial & in-service) in service) Temperature normal

8” 8

T

1”Φ bolts b l typ.

4” 4 4 4”

5 1/8 x 12 glulam

3” 3””” 6” 6””

CD - Load duration CM - Wet Service Ct - Temperature Cg - Group action CD - Geometry, G t applied li d when h spacing i and end or edge distances are less th optimal than ti l Ctn - Toe-nail factor Fe ϴ - Angle of grain adjustment

1”Φ bolts typ.

T

Multiple-Bolt Multiple Bolt Tension Connection

Wet Service Factors Factors, CM

Find Geometry Factor, CΔ Find Geometry Factor, C Check spacing and end/edge distance requirements: End distance End distancemin = 7D = 7(1”) = 7 in