ASD and LRFD with the 2005 NDSwith the 2005 NDS Part 2 ... · Design (LRFD) Design (LRFD) --MandatoryMandatory Chapters10Chapters 10-13MechanicalConnections13 Mechanical Connections

ASD and LRFD ASD and LRFD with the 2005 NDSwith the 2005 NDS®®with the 2005 NDSwith the 2005 NDSPart 2 Part 2 –– Connection DesignConnection Design

Presented by:Presented by:John “Buddy” Showalter P EJohn “Buddy” Showalter P E

Copyright © 2007-2010 American Wood Council. All rights reserved.

John Buddy Showalter, P.E.John Buddy Showalter, P.E.Vice President, Technology TransferVice President, Technology Transfer

OutlineOutline• Connection philosophyp p y• NDS Chapter-by-chapter description• Changes from previous editions• Examples

• Part 1: Member Design Webinar• Available at WoodWorks org• Available at WoodWorks.org


Connection PhilosophyConnection Philosophy

Tension perpendicular to grain• Tension perpendicular to grain– Wood’s weak link

Avoid if possible– Avoid if possible– Reinforce if not

initiators:• Notches• Hanging loads• EccentricityEccentricity


NotchingNotching

Problem Solution


Hanger to BeamHanger to Beam

Lower half of beam– may cause splitsmay cause splits– not recommended

Split


Hanger to BeamHanger to Beam

Upper half of beam– extended plates

move fasteners awayTop bearing option

move fasteners away from tension side of bending member

Compression side of the bending member


g

Beam to ConcreteBeam to Concrete

Notched Beam Bearing– may cause splitting– not recommended

Split



Notched Bearing Wall– alternate to beam notch



Sloped Beam– not fully supported– may split– exposes end grain– not recommended

Split



Sloped Beam– notched concrete wall– alternate to beam notch


OutlineOutline• Connection philosophyp p y• NDS Chapter-by-chapter description• Changes from previous editions• Examples


NDS 2005 ChaptersNDS 2005 Chapters200520051 General Requirements for Building Design1 General Requirements for Building Design2 Design Values for Structural Members2 Design Values for Structural Members3 Design Provisions and Equations3 Design Provisions and Equations4 Sawn Lumber4 Sawn Lumber4 Sawn Lumber4 Sawn Lumber5 Structural Glued Laminated Timber5 Structural Glued Laminated Timber6 Round Timber Poles and Piles6 Round Timber Poles and Piles7 Prefabricated Wood I7 Prefabricated Wood I--JoistsJoists8 S C8 S C8 Structural Composite Lumber8 Structural Composite Lumber9 Wood Structural Panels9 Wood Structural Panels10 Mechanical Connections10 Mechanical Connections11 Dowel11 Dowel--Type FastenersType FastenersT d ’ f {11 Dowel11 Dowel Type FastenersType Fasteners12 Split Ring and Shear Plate Connectors12 Split Ring and Shear Plate Connectors13 Timber Rivets13 Timber Rivets14 Shear Walls and Diaphragms14 Shear Walls and Diaphragms15 S i l L di C diti15 S i l L di C diti

Today’s focus {


15 Special Loading Conditions15 Special Loading Conditions16 Fire Design of Wood Members16 Fire Design of Wood Members

NDS 2005 Appendices20052005A Construction and Design PracticesA Construction and Design Practices

NDS 2005 Appendices

ggB Load DurationB Load DurationC Temperature EffectsC Temperature EffectsD Lateral Stability of BeamsD Lateral Stability of BeamsE Local Stresses in Fastener GroupsE Local Stresses in Fastener Groups Important!ppF Design for Creep and Critical Deflection F Design for Creep and Critical Deflection

ApplicationsApplicationsG Effective Column LengthG Effective Column LengthH Lateral Stability of ColumnsH Lateral Stability of Columns

Important!

yyI Yield Limit Equations for ConnectionsI Yield Limit Equations for ConnectionsJ Solution of Hankinson EquationJ Solution of Hankinson EquationK Typical Dimensions for Split Ring and Shear K Typical Dimensions for Split Ring and Shear

Plate ConnectorsPlate ConnectorsL Typical Dimensions for Standard Hex Bolts, Hex L Typical Dimensions for Standard Hex Bolts, Hex

Lag Screws, Wood Screws, Common, Box, Lag Screws, Wood Screws, Common, Box, and Sinker Nailsand Sinker Nails

M Manufacturing Tolerances for Rivets and Steel M Manufacturing Tolerances for Rivets and Steel


ggSide Plates for Timber Rivet Connections Side Plates for Timber Rivet Connections

N Appendix for Load and Resistance Factor N Appendix for Load and Resistance Factor Design (LRFD) Design (LRFD) -- MandatoryMandatory

Chapters 10 13 Mechanical ConnectionsChapters 10-13 Mechanical Connections• Chapter 10 – mechanical connections• Chapter 11 – dowel-type connectors

(nails, bolts, lag/wood screws)• Chapter 12 – split rings and shear plates• Chapter 13 – timber rivets


Chapter 10 Mechanical ConnectionsChapter 10 – Mechanical Connections10.2.2 Multiple Fastener ConnectionsWhen a connection contains two or more fasteners of the same type and similar size, each of which exhibits the same yield mode (see Appendix I), the total adjusted design value for the connection h ll b th f th dj t d d i l f h i di id lshall be the sum of the adjusted design values for each individual

fastener. Local stresses in connections using multiple fasteners shall be checked in accordance with principles of engineering mechanics (see 10 1 2)mechanics (see 10.1.2).


Chapter 10 Mechanical Connections10.1.2 Stresses in Members at C

Chapter 10 – Mechanical Connections

Connections…Local stresses in connections using multiple fasteners shall beusing multiple fasteners shall be checked in accordance with principles of engineering mechanics. O th d f d t i i thOne method for determining these stresses is provided in Appendix E.


2005 NDS Appendix E2005 NDS Appendix E

•• Appendix EAppendix E Local Stresses in Fastener GroupsLocal Stresses in Fastener Groups•• Appendix EAppendix E -- Local Stresses in Fastener GroupsLocal Stresses in Fastener Groups• new topic introduced in 2001 NDS


Local Stresses in Fastener GroupsLocal Stresses in Fastener Groups

• Closely spaced fasteners– brittle failure– lower capacity

wood failure mechanisms need to be considered in design


L l St i F t GLocal Stresses in Fastener Groups

• Properly spaced fasteners– increased ductility– higher capacity

spread out the fasteners!


Local Stresses in Fastener Gro psLocal Stresses in Fastener Groups

Appendi EAppendi E NDS E pressions•• Appendix EAppendix E NDS Expressions– Net tension:

nettNT AFZ ''

– Row tear-out:

tsFnZ ''

row

i

i

n

iRTRT

viRT

ZZ

tsFnZ

1

''

min


L l St i F t GLocal Stresses in Fastener Groups

•• Appendix EAppendix E NDS Expressions•• Appendix EAppendix E NDS Expressions– Group tear-out

'

netgrouptbottomRTtopRT

GT AFZZZ

'''

'22

• Note: spacing between outer rows of fasteners paralleling the member

i l li l t < 5″


on a single splice plate < 5″

Fasteners on Common Splice PlateFasteners on Common Splice Plate

Good detailing to allow for shrinkage


Local Stresses in Fastener GroupsLocal Stresses in Fastener GroupsExampleTruss Bottom Chord and Splice• Design the bottom chord of a sawn lumber

commercial/industrial truss to support acommercial/industrial truss to support a tensile force (T) of 20,000 lbs (D+L)

• Assume a dry moisture service condition, un-incised material and a load durationun-incised material and a load duration factor of 1.0.


L l St i F t GLocal Stresses in Fastener GroupsExampleTruss Bottom Chord and Splice• The chord includes connections with two rows

of 7/8″ bolts (in a 1/16″ oversized hole)of 7/8 bolts (in a 1/16 oversized hole) spaced per NDS Section 11.5 for full design values. Check the local stresses to verify your member size selection.member size selection.


Local Stresses in Fastener GroupsLocal Stresses in Fastener GroupsSolution

T 4 12 N 1 H Fi• Try 4x12 No.1 Hem Fir:

T′ = 24,600 lbs


Local Stresses in Fastener GroupsLocal Stresses in Fastener GroupsSolution

Si l h t l li l t• Single shear steel splice plate• Neglect eccentricity• Rows spaced at 1/3 depth – within NDS limits

3 75″3.75

3.75″

3 75″3.75



S l tiSolutionUsing Appendix E provisions:Net Section Tension

Net cross section area = (3.5)(11.25 - 2(0.875 + 0.0625)) = 32.8 in.2

ZNT= 625(32.8) = 20,500 lbs > 20,000 lbs OK

11.25”3.5″

7/8″ + 1/16″


11.25

7/8″ + 1/16″

Local Stresses in Fastener GroupsLocal Stresses in Fastener Groups7D = 7(0.875″) = 6.125″

SolutionUsing Appendix E provisions:

( )

3.753.75″ > 1.5D = 1.31> 1.5D = 1.31″ • Row Tear-out Capacity

From the NDS SupplementFv = 150psi 4D = 4(0.875″) = 3.5″

v pCritical spacing scritical is lesser of end distance (7D)or fastener spacing (4D) = 4(0.875″) = 3.5″

ZRT= nrow ni Fvt scritical = (2)(8)(150)(3.5)(3.5) = 29,400 lbs > 20,000 lbs OK



SolutionUsing Appendix E provisions

G T t C it3.75″”

• Group Tear-out CapacityAssume:– uniform row spacing

11.25″3.75″

– edge distance = 3.75 inchesZGT= ZRT/2 + Ft Agroup-net

= (29,400) / 2 + 625(3.5) [11.25 – 2(3.75) - (0.875 + 0.0625)]= 20,850 lbs > 20,000 lbs OK

The design is still acceptable. Net section tension controls.


The design is still acceptable. Net section tension controls.


Alternate: maximum spacing between rowsUsing Appendix E provisions:

G T t C it3.125″

• Group Tear-out CapacityAssume:– 5″ max between rows

11.25″

3.125″

5″ max

– edge distance = 3.125″ZGT= ZRT/2 + Ft Agroup-net

= (29,400) / 2 + 625(3.5) [11.25 – 2(3.125) - (0.875 + 0.0625)]= 27,688 lbs > 20,000 lbs OK

The design is still acceptable


The design is still acceptable.

L l St i F t GLocal Stresses in Fastener GroupsAlternate: minimum spacing between rowsp g

Using Appendix E provisionsG T t C it

4.97″• Group Tear-out Capacity

Assume:– Spacing between rows 1.5D

11.25″4.97″

1.31″

– 1.5D = 1.31 inchesZGT= ZRT/2 + Ft Agroup-net

= (29,400) / 2 + 625(3.5) [1.31 – (0.875 + 0.0625)]= 15,515 lbs < 20,000 lbs NG

The design is unacceptable.


The design is unacceptable. Spacing between rows is too tight!

Chapter 10 Mechanical ConnectionsChapter 10 – Mechanical Connections• Adjustment factors

– Cg

– C

C– Cd

– Ceg

– CCst

– Cdi

– Ctntn


Group Action Factor CGroup Action Factor, CgMultiple fastener connections• accounts for load distribution within the connection• Split rings, shear plates, dowels < 1″• tabulated values still in the NDS• can calculate Cg if outside tabulated range


Group Action Factor CGroup Action Factor, CgCg definitions• row of fasteners

– 2 or more split ring or shear plate connector units aligned in the direction of loadunits aligned in the direction of load

– 2 or more bolts of same diameter loaded in direction of load2 or more lag screws of same type and size– 2 or more lag screws of same type and size loaded in direction of load


Group Action Factor CGroup Action Factor, Cg

• Equation methodq

RmmC EA

n 1)1( 2

h

mmmmRn

C nnEA

g 1111 2

where:

ss

mm

mm

ssEA AE

AEAEAER or oflessor the

12 uum

AEAEsu 112

1


ssmm AEAE2


• Load / slip modulus, (lb/in.)

D = diameter of bolt or lag screw (in.) (lb/in)

Bolts, lag screws: wood to metal connections

(270,000)(D1.5) wood-to-metal connections

Bolts, lag screws: wood-to-wood connections

(180,000)(D1.5)

2-1/2″ split ring & 2-5/8″ shear plate

400,000

4″ split ring & 4″ shear plate 500 000


4 split ring & 4 shear plate

500,000


• Equation method Exampleq pFind Cg for two rows of 1″ diameter bolts spaced 4″ apart in a wood-to-wood double shear splice connection using 2x12’s for main and side members

Am0.5As 2 1.5 in 11.25 inAm 1.5in 11.25 in

Es 1400000psiEm 1400000psiWood Data

104i

Am 16.875 in2

Assm

F t D t

D 1in

n 10s 4inFastener Data


1.8 105lbfin

180000lbf

in2.5D1.5Load / Slip


• Equation method ExampleEquation method Example



• Tabulated values

A = gross x-sectional area ofAm gross x sectional area of main member, in2

A s m of gross sectionalAs = sum of gross x-sectional areas of all side members, in2



• Tabulated ValuesTabulated Values Example

A /A > 1 0 A /A• As/Am > 1.0, so use Am/As= 0.5 to enter column 1 of the table

• also, use Am for column 2 according to Note 1 (Am = 16.875 in2)( m 6.875 )

• read across to column for 10 fasteners in a row


• interpolate Cg = 0.665 ≈ 0.669 from calculation

Group Action Factor CGroup Action Factor , Cg

Not applicable here loads acting along theNot applicable here - loads acting along the length of the member are unit loads

Anchor Bolts andWashers as required

Bottom Plate


Chapter 10 – Mechanical ConnectionsChapter 10 – Mechanical Connections

• Wet Service Factor, CMWet Service Factor, CM


Wet Service Factor CWet Service Factor, CM

Saturated • Dowel-type connectors• bolts• drift pins

19% MCp

• drift bolts• lag screws• wood screwsfabrication MC

in service MC

Dry

*

• nailsin-service MC

CM 1.0 0.7 0.4* Lateral load (*CM=0.7 for D<1/4″)1.0 0.7 1.0 Withdrawal load - lag & wood screws only1.0 0.25 0.25 Withdrawal load - nails & spikes


p

Wet Service Factor CWet Service Factor, CM

Saturated CCMM = 1.0 if:= 1.0 if:

19% MC

fabrication MCi i MC

1 fastener

Dry

in-service MC2+ fasteners

CM 0.4 Lateral load (D>1/4″)split splice plates


Fasteners on Common Splice PlateFasteners on Common Splice Plate

Good detailing to allow for shrinkage


Chapter 11 Dowel type FastenersChapter 11 – Dowel-type FastenersASD and LRFD accommodated through Table 10.3.1g– Bolts– Lag screws– Wood screws– Nails & spikes


Fastener ValuesFastener Values

Included in U S design literatureIncluded in U.S. design literatureFastener Type Reference Bolts NDS or NER Lag Screws NDS or NER Wood Screws NDS or NER Nails & Spikes NDS or NERNails & Spikes NDS or NER Split Ring Connectors NDS Shear Plate Connectors NDS D ift B lt & D ift Pi NDS

National Evaluation Reports (NER) are developed forDrift Bolts & Drift Pins NDS

Metal Plate Connectors NER Hangers & Framing Anchors NER

developed for proprietary products


Staples NER

Fastener Bending YieldFastener Bending Yield


Fastener Bending Yield TestFastener Bending Yield Test

Center-Point Bending Test

Load


Dowel Bearing StrengthDowel Bearing Strength


Yield Limit EquationsYield Limit Equations

•6 Yield Modes•Single & double shear•Wood-to-wood•Wood-to-Steel•Wood-to-Concrete



II

IIII

IIIIII

IV


IV



Nail Types and DesignationsNails and nomenclatureNail Types and Designations

• box nail• ring shank nail• common nail• sinker• pneumatic


Nail Types and DesignationsNail Types and DesignationsNail types described in Appendix Lyp pp


Nail Types and DesignationsNail Types and DesignationsNail capacity tables in 2005 NDSp y


Penetration Depth Factor CPenetration Depth Factor, Cd• Changed in 2001 NDS

P t ti i b ilt i t Yi ld Li it E ti• Penetration is built-in to Yield Limit Equations:– m main member dowel bearing length– s side member dowel bearing length

• Tables for lag screws, wood screws, and nails:– Based on 8D, 10D, and 10D penetrations, respectively– Reduced penetration? Use Table FootnotesReduced penetration? Use Table Footnotes

• FAQ available at awc.org


Fastener PenetrationFastener Penetration

Fastener Type Minimum

Lag Screws 4D

Wood Screws 6D

Nails & Spikes 6DNails & Spikes 6D

NDS 11.3.4 “…The length of dowel bearing shall notNDS 11.3.4 …The length of dowel bearing shall notinclude the length of the tapered tip of a fastener forfastener penetration lengths less than 10D.”


Penetration NailsPenetration - Nails• P = 6D (NDS 11.1.5.5)

6D


Penetration Wood ScrewsPenetration – Wood Screws• P = 6D (NDS 11.1.4.6) - includes tip

6D


Penetration Lag ScrewsPenetration – Lag Screws• P = 4D (NDS 11.1.3.6) - does not include tip

4D


Dowel Diameter Lag ScrewsDowel Diameter – Lag ScrewsReduced Body Diameter• Dr used to calculate capacity regardless of

shear plane location (NDS 11.3.6.1)

nesh

ear p

lan

Dr


Lateral CapacityLateral CapacityFull Body Diameter• Dr used to calculate capacity if threads are in

or near the shear plane (NDS 11.3.6.2)use Dr

Copyright © 2007-2010 American Wood Council. All rights reserved.shear plane

Lateral Capacity Lag ScrewsLateral Capacity – Lag Screws• Why no threads near the shear plane?

Because the induced maximum moment canmaximum moment can occur in the threads if the shear plane is not l t d ffi i tl i tlocated sufficiently into the shank away from the threads


Lateral Capacity Lag ScrewsLateral Capacity – Lag Screws• Info on where to locate the shear plane


Lateral Capacity Wood ScrewsLateral Capacity – Wood ScrewsRolled Thread• Dr used to calc capacity if shear plane is

anywhere (NDS 11.3.6.1)

esh

ear p

lane

s


Lateral Capacity Wood ScrewsLateral Capacity – Wood ScrewsCut Thread• Dr used to calc capacity if shear plane is in or

near the threads (NDS 11.3.6.2)

use Druse D

hear

pla

ne~ 3D to 4Dr

sh


Toe nailingToe nailing

WithdrawalWithdrawal– Ctn = 0.67

Lateral– Ct = 0 83Ctn = 0.83


Chapter 11 ConnectionsChapter 11 – Connections• Capacity definitions

– Z||

– Zm

Z– Zs

– Z


Spacing End & Edge DistancesSpacing, End, & Edge Distances


Nail Capacity CalculationsNail Capacity Calculations• Example: Shear Wall p

Chord Ties with Nails– ASD & LRFD


Nailed Tension TieNailed Tension Tie

H il f thi ti ?How many nails for this connection?Design connection ties between first and second floor shear wall

A653

first and second floor shear wall chords. Walls are 2x6, dry Douglas Fir-Larch studs spaced t 16” Th ifi d i dat 16” oc. The specified wind

overturning force is 2.4 kips.


Nailed Tension Tie LRFD & ASDNailed Tension Tie – LRFD & ASDTry:y• ASTM A653 Grade metal

strap16 gage x 2.5” wide• 2 rows staggered 10d2 rows staggered 10d

common nails


Nailed Tension Tie LRFD & ASDNailed Tension Tie – LRFD & ASD

2005 NDS Table 11P

Z 116 lbZ = 116 lbs


Nailed Tension Tie LRFD & ASDNailed Tension Tie – LRFD & ASD2005 NDS Table 11P, Table 10.3.1, and Appendix Npp

LRFD ASDADJUSTMENT FACTORSTime dependent = 1.0 Table N3 CD = 1.6Wet service CMTemperature CtGroup Action CgG t C

D1.0 1.01.0 1.01.0 1.0

Geometry CEnd grain CegDiaphragm CdiToe nail C

1.0 1.01.0 1.01.0 1.01 0 1 0Toe nail Ctn

Penetration 3” > 10D

Format conversion KF

1.0 1.01.0 1.0

2 16 / = 3 32 Table N1


Format conversion KFResistance z

2.16 / z = 3.32 Table N10.65 Table N2


DEMAND Wind Overturning

LRFD ASD

DEMAND – Wind Overturning

w = W Ww = ot Wot= (1.6)(2,400)= 3,840 lbs

w = Wot= 2,400 lbs



CAPACITY

LRFD ASD

CAPACITYSafety Limit State

LRFD ASDZ’ = Z z KF (all C factors)

= (116)(0.65)(1.0)(3.32)(1.0)250 lb

Z’ = Z CD (all C factors) = (116)(1.6)(1.0)

= 250 lbs = 186 lbs

Nails Needed

n = w / Z’ = (3,840) / (250)= 15 4 16 nails

n = w / Z’ = (2,400) / (186)= 12 9 13 nails


= 15.4 16 nails = 12.9 13 nails


CAPACITYCAPACITYSafety Limit State

LRFD ASDLRFD ASDw Z’ W Z’

3 840 lbs 4 000 lbs 2 400 lb 2 976 lb

d d itd d it

3,840 lbs 4,000 lbs 2,400 lbs 2,976 lbs

demand capacitydemand capacity

0 96 0 81Demand / Capacity Ratio


0.96 0.81Demand / Capacity Ratio

16 Nails 13 Nails


• Why the ASD / LRFD discrepancy?y p y– 2005 NDS format conversion does not benefit

LRFD in the Wind Only case– Real benefits are realized with combined multiple

transient loads (ie. wind + snow + live) – examine load combination cases and LRFD load factors inload combination cases and LRFD load factors in addition to relative magnitudes of the loads themselves


Connection CalculatorConnection Calculator

AWC.org


Chapter 12 Split Rings and Shear PlatesChapter 12 – Split Rings and Shear Plates• Capacity tables - unchanged


Chapter 12 Split Rings and Shear PlatesChapter 12 – Split Rings and Shear Plates

AvailabilityAvailability• www.clevelandsteel.com


Chapter 13 Timber RivetsChapter 13 – Timber Rivets• Capacity tables and details - unchanged


Chapter 13 Timber RivetsChapter 13 – Timber Rivets• Many applications


Ch t 13 Ti b Ri tChapter 13 – Timber RivetsRivetsRivets• Steel AISI 1035• Rockwell Hardness C32-39• Fu = 145 ksiFu 145 ksi• Hot-dipped galvanized

PlatesPlates• Steel ASTM A36• Hot-dipped galvanized if in

wet serviceet se ce


Timber Rivets DesignTimber Rivets - Design• Four strength limit states:

– Rivet yielding• Pr – parallel to grain• Q – perpendicular to grainQr perpendicular to grain

– Wood failure• Pw – parallel to grain• Qw – perpendicular to grain

Plate yielding– Plate yielding• Enhanced ductility


Lowest value governs design

DES110:DES110:Connection DesignConnection Design

••www.awc.orgwww.awc.org••MoreMore comprehensivecomprehensive


pp••CEU’s availableCEU’s available

QUESTIONS?QUESTIONS?

PhonesPhonesGeneral: (202) 463 2766Helpdesk: (202) 463 4713Publications: (800) 890 7732

EmailPublications: [email protected]: [email protected]: info@awc orgTechnical: [email protected]

Website


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Documents

ASD and LRFD with the 2005 NDSwith the 2005 NDS Part 2 ... · Design (LRFD) Design (LRFD) --MandatoryMandatory Chapters10Chapters 10-13MechanicalConnections13 Mechanical Connections