connection design examples - awc.org familiar with nds provisions for fastener withdrawal capacity...

Connection Design ExamplesUsing the 2015 NDS (DES345)

Lori Koch, P.E.Manager, Educational OutreachAmerican Wood Council

Adam Robertson, M.A.Sc., P.Eng.Manager, Codes and StandardsCanadian Wood Council

DES 345 – Conne c t i o n De s i g n E x amp l e s

COURSE DESCRIPTION

With the variety of fasteners available for wood construction, this presentation will provide a basic understanding of connections that includes design examples based on the 2015 National Design Specification® (NDS®) for Wood Construction. Solutions for nailed, screwed, and bolted connections will be presented, along with specific information on calculating shear capacity as well as withdrawal capacity. Multiple approaches to calculating capacity will be discussed, including tabulated references, calculation-based techniques, and computer program solutions (including WoodWorks® Connections software). Material properties for fasteners as well as connected materials including wood-to-wood, wood-to-steel, and wood-to-concrete will be discussed.

Disclaimer: Portions of this presentation were developed by a third party and are not funded by American Wood Council or the Softwood Lumber Board.


Participants may download the presentation here: http://www.awc.org/education/resources

The American Wood Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider # 50111237.

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 request.

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.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.


LEARNING OBJECTIVESUpon completion, participants will be better able to identify:

Be familiar with NDS provisions for fastener withdrawal capacity and NDS and TR-12 provisions for fastener shear capacity

Withdrawal and Shear Loading

Learn various approaches in the NDS for calculating fastener capacity

NDS-based Calculations

Understand the 6 lateral design value yield modes and material properties used to calculate capacity

Lateral Yield Modes

Understand the types of connections WoodWorks® software designs, how to use the software, how to view the design results and the connection drawing output

Software-based Solutions

1 3

2 4


OUTLINE

NDS Provisions on Connection Design

Introduction

Force is applied parallel to the length of the fastener

Withdrawal Examples

Force is applied perpendicular to the length of the fastener

Shear Examples

Examples using WoodWorks® software

Computer Aided Solutions

1 3

2 4


POLLING QUESTION

What is your profession?a) Engineerb) Architectc) Building Officiald) Other

6


NDS CH. 11 – MECHANICAL CONNECTIONS

Design issues

Reference design valuesChapter 12 – dowel-type connectors (nails, bolts, lag/wood screws)

Chapter 13 – split rings and shear plates

Chapter 14 – timber rivets

Adjustment factors

7


NDS CH. 11 – MECHANICAL CONNECTIONS

8


NDS CH. 12 – DOWEL-TYPE FASTENERS

Withdrawal Equations for Dowel-Type Fasteners

• Lag screws W = 1800 G3/2 D3/4

• Wood screws W = 2800 G2 D

• Smooth shank nails (bright or galvanized carbon steel)W = 1380 G5/2 D

• Post-frame ring shank nails W = 1800 G2 D

9



Withdrawal Penetration

• Lag screws Do NOT include length of tapered fastener tip in penetration

• Wood screws, Nails/Spikes Include length of tapered fastener tip in penetration

10



Withdrawal based on inches of penetration into main member

11


WITHDRAWAL EXAMPLES

Withdrawal examples

• Smooth shank nail

• Lag screw

12

Withdrawal Design Value - Plain Shank Nail

Using 2015 NDS section 12.2, calculate the Allowable Stress Design (ASD) referencewithdrawal capacity of an 8d common plain shank nail in the connection below: Main member: Spruce-Pine-Fir Nominal 4x (Actual dimension 3.5 in.) (G = 0.42)

Side member: 12 gage (0.105 in. thick) ASTM A653 Grade 33 steel side plate Fastener Dimensions: 8d nail (NDS Table L4) Length = 2.5 in. Diameter = 0.131 in.

D 0.131 Fastener diameter (in.)

G 0.42 Specific gravity (NDS Table 12.3.3A)

L 2.5 Nail Length (in.)

Ls 0.105 Side Member thickness (in.)

pt L Ls Nail penetration into main member (in.)

pt 2.395

W 1380 G

5

2 D NDS Equation 12.2-3

W 20.7 Reference withdrawal design value. Compare to NDS Table12.2C, W = 21 lbs/in

Resistance pt W Resistance based on main member penetration (lbs)

Resistance 49 AWC Online Connection Calculator gives identical result of 49 lbs

See NDS Table 11.3.1 for application of additional adjustment factors for connections based onend use conditions.

Withdrawal Design Value - Lag Screw

Using 2015 NDS provisions (NDS 12.2) calculate the Allowable Stress Design (ASD) withdrawalcapacity of a lag screw in the connection below: Main member: Southern Pine Nominal 6x (Actual thickness = 5.5 in.) (G = 0.55) (NDS Table 12.3.3A) Side member: Southern Pine Nominal 2x (Actual thickness = 1.5 in.) (G = 0.55) (NDS Table 12.3.3A) Fastener Dimensions: 1/2 in. diameter lag screw (NDS Table L2) Length = 4 in. Tip Length = 0.3125 in.

D 0.5 Fastener diameter (in.)

tip 0.3125 Fastener tapered tip length (in.)

G 0.55 Specific gravity (NDS Table 12.3.3A)

L 4 Lag screw length (in.)

Ls 1.5 Side Member thickness (in.)

pt L Ls tip Lag screw penetration into main member (in.)

pt 2.188

W 1800 G

3

2 D

3

4 NDS Equation 12.2-1

W 436.6 Compare to NDS Reference Withdrawal Design Value Table12.2A, W = 437 lbs/in.

Resistance pt W Resistance based on main member penetration (lbs)

Resistance 955 AWC Online Connection Calculator gives identical result of 955 lbs

See NDS Table 11.3.1 for application of additional adjustment factors for connections based on enduse conditions.



•4 Yield Modes•6 Yield Equations•Single & Double Shear•Wood-to-Wood•Wood-to-Steel•Wood-to-Concrete

Members must be in contact at shear plane – NO GAPS!

13


YIELD MODES

MODE I• bearing-dominated yield of

wood fibers

MODE II• pivoting of fastener with

localized crushing of wood fibers

MODE III•fastener yield in bending at one plastic hinge and localized crushing of wood fibers

MODE IV• fastener yield in bending at

two plastic hinges and localized crushing of wood fibers

14


POLLING QUESTION

The NDS Yield Limit Equations for Modes II and IIIm do not apply to Single Shear connections.a) Trueb) False

15


DOWEL BEARING STRENGTH

16


FASTENER BENDING YIELD STRENGTH

Load

17


FASTENER BENDING YIELD STRENGTH

Fastener Bending Yield Strength (Fyb) sources:• NDS Appendix I• TR-12 Appendix A• Manufacturer’s data• ICC Evaluation Service Report• ASTM F1667 Appendix

18



New

19



New

Non-uniform for

CLT

20


• Adjust lm or ls to compensate for orthogonal grain orientations in adjacent layers

• Parallel to grain: Fe/FeǁExample: ½” bolt in southern pine 3-ply CLT

with 1-½” laminationslm = t1ǁ + t2 + t3ǁ = 3(1.5) = 4.5”lm-adj = t1ǁ + t2(Fe/Feǁ) + t3ǁ

=1.5 +1.5(3650/6150) +1.5 = 3.9”


21



22



Threaded length < lm/4 lm

Dia. Fastener = D

Dia. Fastener = D

Threaded length < lm/4 lm

23



Dia. Fastener = Dr

NDS Chapter 12 Tables use: • Dr for lateral yield equations for lag screws and wood screws • D for bolts

lm

24


FASTENER BEARING LENGTH

Tapered tip length, E:• Dimensions for Lag Screws in NDS Appendix L• Wood screws, Nails/Spikes

• Tip length, E = 2D• Bearing length = penetration – E/2• 6D minimum penetration for nails*, spikes, wood screws• 4D minimum penetration for lag screws

*Exception for double shear connections with clinched nails, D ≤ 0.148”

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http://www.awc.org/publications/TR/index.php

TECHNICAL REPORT 12

Provide tools for the analysis of• gaps between members• various fastener bending moment configurations• fasteners through hollow members• fasteners with tapered tips

Provides mechanics-based approach to Lateral Connection Design

Calculate “P” value with TR-12 equations• divide by Rd (NDS Table 12.3.1B) to get “Z” equal to NDS values

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http://www.awc.org/publications/TR/index.php

TECHNICAL REPORT 12

• Provides design values inputs for various materials

• Dowel bearing strengths (Fe)

• Fastener bending yield strengths (Fyb)

TR-12 Appendix A

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SINGLE SHEAR NAIL EXAMPLE

Compare to NDS Table 12N value:Z = 121 lbs

Nail Size 10d Mode Im 785

Diameter (in.) 0.148 Mode Is 280

Fyb (psi) 90000 Mode II 262

Length (in.) 3 Mode IIIm 272

Mode IIIs 121Mode IV 128

Main Member Thickness (in.) 2.5Main Member Species Southern Pine Z (lbs) = 121Main Member Dowel Bearing Strength (Fem) (psi) 5550

Side Member Thickness (in.) 0.75Side Member Species Southern Pine Side Member Dowel Bearing Strength (Fes) (psi) 5550

Side Member Bearing Length (Ls) (in.) 0.75Main Member Penetration (p) (in.) 2.25Tapered Tip Length (E) (in.) 0.296Main Member Bearing Length (Lm) (in.) 2.102

Calculated Inputs

Yield Mode CalculationsSingle Nail ‐ Single ShearNail Properties

Main Member Properties

Side Member Properties

28


SHEAR EXAMPLES

Additional shear examples

• Smooth shank nail – single shear

• Wood Screw – double shear

• Bolt – single shear

29

Single Common Nail Lateral Design Value - Single Shear Wood-to-wood Connection Using the 2015 NDS yield limit equations in section 12.3, determine the Allowable StressDesign (ASD) reference lateral capacity of a single shear connection with the followingconfiguration:

Main member Nominal 3x Southern Pine (Actual thickness = 2.5 in.) (G = 0.55) (NDS Table 12.3.3A)

Side member Nominal 1x Southern Pine (Actual thickness = 0.75 in.) (G = 0.55) (NDS Table 12.3.3A) Fastener Dimensions: 10d Common Nail (NDS Table L4) D = 0.148 in. Length = 3 in.

Define parameters:

Fem 5550 Main member Dowel Bearing Strength (NDS Table 12.3.3) (psi)

Fes 5550 Side member Dowel Bearing Strength (NDS Table 12.3.3) (psi)

Re

Fem

Fes

Re 1

Fyb 90000 Fastener dowel bending yield strength (psi) (NDS Table I1)

D 0.148 Nail Diameter (in.)

Tip 2 D Length of tapered fastener tip (in.) (NDS 12.3.5.3b)

Ls 0.75 Side member Dowel Bearing Length (in.) (NDS 12.3.5)

Lm 3 LsTip

2 Main member Dowel Bearing Length (in.) (NDS 12.3.5.3)

Lm 2.1

NDS 12.1.6.5 Requires minimum main member penetration equal to 6D, Lm > 0.89 in.

Rd 2.2 Reduction Term (NDS Table 12.3.1B)

Calculate k 1 , k 2 , and k 3 (NDS Table 12.3.1A)

Rt

Lm

Ls Rt 2.803

k1

Re 2 Re2

1 Rt Rt2

Rt

2Re

3

Re 1 Rt

1 Re

k1 0.935

k2 1 2 1 Re 2 Fyb 1 2 Re D

2

3 Fem Lm2

k2 1.04

k3 12 1 Re

Re

2 Fyb 2 Re D2

3 Fem Ls2

k3 1.294

Yield Mode Calculations (NDS Table 12.3.1A)

Mode Im

ZIm

D Lm Fem

Rd

ZIm 785 Yield Mode Im Solution (lbs)

Mode Is

ZIs

D Ls Fes

Rd

ZIs 280 Yield Mode Is Solution (lbs)

Mode II

ZII

k1 D Ls Fes

Rd

ZII 262 Yield Mode II Solution (lbs)

Mode IIIm

ZIIIm

k2 D Lm Fem

1 2 Re Rd

ZIIIm 272 Yield Mode IIIm Solution (lbs)

Mode IIIs

ZIIIs

k3 D Ls Fem

2 Re Rd

ZIIIs 121 Yield Mode IIIs Solution (lbs)

Mode IV

ZIVD2

Rd

2 Fem Fyb

3 1 Re

ZIV 128 Yield Mode IV Solution (lbs)

Zdist

ZIm

ZIs

ZII

ZIIIm

ZIIIs

ZIV

Zdist

785

280

262

272

121

128

Creating an array with all Yield Mode Solutions

Z min Zdist

Z 121 Minimum value of all Yield Modes provides Z reference lateraldesign value (lbs). Mode IIIs controls. Compare to NDS Table 12Nvalue = 121 lbs. See NDS Table 11.3.1 for application ofadditional adjustment factors for connections based on end useconditions.

Single Wood Screw Lateral Design Value - Double Shear Wood-to-wood Connection Using 2015 NDS yield limit equations in section 12.3, determine the allowable stress designreference lateral design value of a double shear connection with the following configuration:

Main member Actual 3 in. Structural Composite Lumber Member (G = 0.5) (NDS 12.3.3.3)

Side members Nominal 2x Douglas Fir-Larch (DF-L) (Actual thickness = 1.5 in.) (G = 0.5) (NDS 12.3.3A)

Fastener Dimensions: Number 10 Wood Screw (NDS Table L3) D = 0.19 in. Dr= 0.152 in. Length = 6 in.

Define parameters:



Re

Fem

Fes Re 1

tm 3.0 Main Member thickness (in.)

ts 1.5 Side Member thickness (in.)


D 0.19 Screw Diameter (in.)

Dr 0.152 Screw Root Diameter (in.)

Lscrew 6 Screw Length (in.)

Tip 2 D Length of tapered fastener tip (in.) (NDS 12.3.5.3b)

Lm tm Lm 3 Main member Dowel Bearing Length (in.) (NDS 12.3.5.3)

Ls Lscrew Lm tsTip

2 Side member Dowel Bearing Length (in.) (NDS 12.3.5)

Ls 1.31 NDS 12.1.5.6 requires minimum 6D penetration, Ls>1.14 in.

Rd 10D 0.5 Rd 2.4 Reduction Term (NDS Table 12.3.1B)

Calculate k 3 (NDS Table 12.3.1A) (k 1 and k 2 not used)

k3 12 1 Re

Re

2 Fyb 2 Re Dr2

3 Fem Ls2

k3 1.113


Mode Im

ZIm

Dr Lm Fem

Rd


Mode Is

ZIs

2Dr Ls Fes

Rd


Mode IIIs

ZIIIs

2k3 Dr Ls Fem

2 Re Rd


Mode IV

ZIV

2Dr2

Rd

2 Fem Fyb

3 1 Re


Zdist

ZIm

ZIs

ZIIIs

ZIV

Zdist

883

772

286

214


Z min Zdist

Z 214 Minimum value of all Yield Modes provides Z reference lateral designvalue (lbs). Mode IV controls. There are no tabulated values in the NDSto compare. See NDS Table 11.3.1 for application of additionaladjustment factors for connections based on end use conditions.

Single Bolt Lateral Design Value - Single Shear Wood-to-Wood Connection Using the 2015 NDS Yield Limit Equations (NDS 12.3), determine the Allowable StressDesign (ASD) reference lateral capacity of a single shear connection with the followingconfiguration:

Main member Nominal 4x Hem-Fir (Actual thickness = 3.5")

Side member Nominal 4x Hem-Fir (Actual thickness = 3.5") Both members loaded parallel to grain G = 0.43 for Hem-Fir (NDS Table 12.3.3A)

Fastener Dimensions: 1/2 in. diameter bolt 8 in. Bolt with 1.5 in. thread length (NDS Table L1)

Define parameters:



Re

Fem

Fes

Re 1


D 0.5 Bolt Diameter (in.)

Per NDS 12.3.7.2, check that threads are less than 1/4 the bearing length in the member holdingthe threads. In this case, 3.5 in./4 > 0.5 in. Therefore, OK to use D instead of Dr in calculations.

Ls 3.5 Side member Dowel Bearing Length (in.) (NDS 12.3.5)

Lm 3.5 Main member Dowel Bearing Length (in.) (NDS 12.3.5)

Rd1 4.0

Rd2 3.6 Reduction Terms (NDS Table 12.3.1B)

Rd3 3.2

Calculate k 1 , k 2 , and k 3 (NDS Table 12.3.1A)

Rt

Lm

Ls Rt 1

k1

Re 2 Re2

1 Rt Rt2

Rt

2Re

3

Re 1 Rt

1 Re

k1 0.414

k2 1 2 1 Re 2 Fyb 1 2 Re D

2

3 Fem Lm2

k2 1.093

k3 12 1 Re

Re

2 Fyb 2 Re D2

3 Fem Ls2

k3 1.093


Mode Im

ZIm

D Lm Fem

Rd1


Mode Is

ZIs

D Ls Fes

Rd1


Mode II

ZII

k1 D Ls Fes

Rd2

ZII 966 Yield Mode II Solution (lbs)

Mode IIIm

ZIIIm

k2 D Lm Fem

1 2 Re Rd3

ZIIIm 957 Yield Mode IIIm Solution (lbs)

Mode IIIs

ZIIIs

k3 D Ls Fem

2 Re Rd3


Mode IV

ZIVD2

Rd3

2 Fem Fyb

3 1 Re


Zdist

ZIm

ZIs

ZII

ZIIIm

ZIIIs

ZIV


Minimum value of all Yield Modes provides Z reference lateraldesign value (lbs). Mode IV controls.Z min Zdist Z 663

Repeat same problem, but solve using Technical Report 12 - General Dowel Equations for Calculating Lateral Connection Values (TR-12) Equations for comparison

qs Fes D Side member dowel bearing resistance, lbs/in.

qm Fem D Main member dowel bearing resistance, lbs/in.

Side and Main member dowel resistance (equal due to equivalent doweldiameter in both members), in.-lbsM

Fyb D3

6

gap 0 Gap between member shear planes, in.

The limiting wood stresses used in the yield model are based on the load at which theload-deformation curve from a fastener embedment test intersects a line represented by theinitial tangent modolus offset 5%of the fastener diameter. The reduction term, Rd, reduces thevalues calculated using the yield limit equations to approximate estimates of the nominalproportional limit design valuesin previous NDS editions.

Yield Mode Calculations (TR-12 Table 1-1)

Mode Im

PIm qm Lm

TR-12 Yield Mode Im Solution (lbs)PIm 8400

Mode Is

PIs qs Ls

TR-12 Yield Mode Is Solution (lbs)PIs 8400

Mode II

AII1

4 qs

1

4 qm

BII

Ls

2gap

Lm

2

CII

qs Ls2

4

qm Lm2

4

PII

BII BII2

4 AII CII

2 AII

PII 3479 TR-12 Yield Mode II Solution (lbs)

Mode IIIm

AIIIm1

2 qs

1

4 qm

BIIIm gapLm

2

CIIIm Mqm Lm

2

4

PIIIm

BIIIm BIIIm2

4 AIIIm CIIIm

2 AIIIm

PIIIm 3062 TR-12 Yield Mode IIIm Solution (lbs)

Mode IIIs

AIIIs1

4 qs

1

2 qm

BIIIs gapLs

2

CIIIs Mqs Ls

2

4

PIIIs

BIIIs BIIIs2

4 AIIIs CIIIs

2 AIIIs

PIIIs 3062 TR-12 Yield Mode IIIs Solution (lbs)

Mode IV

AIV1

2 qs

1

2 qm

BIV gap

CIV M M

PIV

BIV BIV2

4 AIV CIV

2 AIV

PIV 2121 TR-12 Yield Mode IV Solution (lbs)

Converting from TR-12 "P" values to NDS "Z"values and creating an array. Shows TR-12results equal NDS results for each YieldMode. All values in units of lbs.

Zdist2

PIm

Rd1

PIs

Rd1

PII

Rd2

PIIIm

Rd3

PIIIs

Rd3

PIV

Rd3

Zdist2

2100

2100

966

957

957

663

Z2 min Zdist2 Z value from TR-12 equations is equivalent to Z value from NDSequations and comparable to NDS Table 12A value Zparallel = 660lb. See NDS Table 11.3.1 for application of additional adjustmentfactors for connections based on end use conditions.

Z2 663

Zdist is NDS equation result, Zdist2 isTR-12 equation result, for Modes Im,Is, II, IIIm, IIIs, and IV, respectively. Allvalues in units of lbs.

Zdist

2100

2100

966

957

957

663

Zdist2

2100

2100

966

957

957

663


POLLING QUESTION

Technical Report 12 can be used to calculate a dowel‐type connection’s:a) Reference withdrawal design valuesb) Reference lateral design values c) Combined lateral and withdrawal reference

design valuesd) Maximum fastener sizes

30


2018 NDS CHANGES – WHAT’S COMING?

Revised withdrawal equations for deformed-shank nails

Inclusion of Roof Sheathing Ring Shank (RSRS) nail

Removal of generic threaded nail withdrawal provision

New equation for stainless steel smooth shank nails

Round-head fastener pull-through

December webinar on 2018 NDS changes!

31


WOODWORKS DESIGN OFFICE 11 SOFTWARE

SHEARWALLS

CONNECTIONS

SIZERGravity Design

Lateral Design (Wind and Seismic)

Fasteners

Concept mode

Column modeBeam mode

DATABASE EDITORAdd proprietary products

woodworks-software.com32



Choose connection geometry:

Lapped shearWood-to-woodSplice, two member

33



Choose fastener type:

Nails

34



Specify properties of main member:

Database editor

35



Database editor:

36



Specify properties of side member:

Database editor

Manual input section sizes37



Specify additional parameters:

Wet service factor (CM)

Temperature factor (Ct)

Fire retardant treatment (Cft)(Unique to WoodWorks –not in NDS)Frequently used load duration factor (CD)

38



Specify fastener properties:

39



Preliminary connection layout:

40



Results:

41



Results:

42


SINGLE SHEAR BOLT EXAMPLE


Lapped shearWood-to-woodSplice, two member

43




Bolts

44



Specify properties of main and side members:

45






Fire retardant treatment (Cft) (Unique to WoodWorks –not in NDS)Frequently used load duration factor (CD)

46




47




48



Results:

49



Results:

50



Results:

51


LAG SCREW WITHDRAWAL EXAMPLE


Post and BeamBeam-to-beamOne-sided

52




Lag screws

53



Specify properties of main and side members:

54






Fire retardant treatment (Cft)(Unique to WoodWorks –not in NDS)Frequently used load duration factor (CD)

55




56




57

Export to CAD file (.DXF format)



Results:

58



Results:

59



Results:

60



Results:

61


ADDITIONAL CONNECTION TYPES

Wood-to-wood:

Wood-to-steel:

Wood-to-concrete:

Export as DXF

62


WOODWORKS DESIGN OFFICE 11 SOFTWARE

SHEARWALLS

CONNECTIONS

SIZERGravity Design

Lateral Design (Wind and Seismic)

Fasteners

Concept mode

Column modeBeam mode

DATABASE EDITORAdd proprietary products

10% discount for AWC members

For more information contact:

[email protected]

[email protected]

63


POLLING QUESTION

The WoodWorks Design Office software has versions for both US and Canadian standards. a) Trueb) False

64


T h i s p r e s e n t a t i o n i s p r o t e c t e d b y U S a n d I n t e r n a t i o n a l C o p y r i g h t l a w s . R e p r o d u c t i o n , d i s t r i b u t i o n , d i s p l a y a n d u s e o f t h e p r e s e n t a t i o n w i t h o u t w r i t t e n p e r m i s s i o n o f A m e r i c a n W o o d C o u n c i l ( A W C ) i s

p r o h i b i t e d . © A m e r i c a n W o o d C o u n c i l 2 0 1 7

in [email protected] | www.awc.org

This concludes the American Institute of Architects Continuing Education Systems Course

connection design examples - awc.org familiar with nds provisions for fastener withdrawal capacity...

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