Connecting the Parts:

Driving to Performance

Simpson Strong-Tie Company Inc. Robert Leichti

Engineering Manager, Fastening Systems

Pleasanton, CA USA

Outline

• Review small-diameter fastener fundamentals;

• Investigate practice for specification of nails and screws;

• Explore some fastener-related issues associated with contemporary fasteners and wood-based construction materials;

• Learn about some new products that address installation specific challenges.

2 11/20/2012

Small-Diameter Fastening for Wood Frame Construction

3 11/20/2012

Small-diameter Fasteners

• Mechanical fasteners, nails, screws, and timber rivets, and others.

• Small diameter ≤ 6 mm (0.25 in.)

• Roles in the building system – Mechanically connect parts to form an assembly with

structural integrity.

– Create vertical and lateral load paths.

– Provide mechanism for ductility with lateral loading.

– Contribute to fire safety.

– Affect serviceability (vibration and sound transmission)

– Facilitate assembly and disassembly.

4 11/20/2012

Small-diameter Fasteners - Design Properties

• Withdrawal - Function of dowel diameter and specific gravity.

• Lateral (aka, “shear”) - Affected by embedding strength of wood or member of other engineering materials, thickness of side member, penetration into main member, bending yield strength of fastener.

• Pull-through- Thickness of side member; usually a screw-related property.

5 11/20/2012

Small-diameter Fasteners – Design Assumptions

• Members are in contact.

• Fasteners penetrate perpendicular to face.

• Nails - thickness and penetration (O86-09, §10.9).

• Lags - Penetration minimum 5dF (O86-09, §10.6.3.3).

• Screws – thickness and penetration same as nails (O86-09, §10.11.2.3).

CSA O86-09, Figure 10.9.2.2 Member thicknesses for nail connections, where thickness and penetration are related to dF = fastener shank diameter.

6 11/20/2012

Small-diameter Fasteners - Yield Limit Model for Lateral

• Yield limit model based on engineering mechanics assumes round headless dowel.

• Primary factors used to compute design values include, – Embedding strength of wood

(main and side members) – Specific gravity of members – Thickness of side member and

penetration length into main member

– Diameter of dowel – Bending yield strength of dowel

• Calculate all solutions, chose least.

7 11/20/2012

Practice for Specification of Small-diameter Fasteners

• Prescriptive and engineered solutions. • NBCC, Section 9.23 specifies CSA B111 for nails and ASME

B18.6.1 for screws. • Engineering Design in Wood O86-09, Section 10.9.1 refers

to nails as defined in CSA B111. • For nails, O86-09, Table A10.9.5.2 links nail sizes of B111 to

prescriptive design per NBCC, Tables 9.23.3.4 – framing and 9.23.3.5 – sheathing and subflooring.

• For lag screws, O86-09, Section 10.6.1.1 references ASME B18.2.1.

• For screws O86-09, Section 10.11.1, references ASME 18.6.1. No prescriptive design guidance in NBCC aside from subfloor fastening.

8 11/20/2012

NAILS: CSA B111-1974 Withdrawn

• Compilation of tables of nails by type and sizes. • Included tolerances and some mechanical performance

properties. • Described galvanization (electro-galvanization and

HDG) to prevent corrosion and other coatings. • Worked for prescriptive fastening in dry-service and

general corrosion conditions. • Pre-dated wide-spread use of pneumatic tools. • Included no engineering guidance with respect to

bending yield strength and no corrosion specifics for today’s treatment chemicals.

9 11/20/2012

B111 Withdrawn - Now What?

• ASTM F 1667-11a, Standard Specification for Driven Fasteners: Nails, Spikes, Staples

• Scope is fasteners driven with a hand tool, power tool, or mechanical device with single and multiple blows.

• Includes 59 tables of different nails, spikes, staples, and includes timber rivets. Construction nails generally in Tables 10-30.

• Tolerances • Mechanical and physical properties • Coatings and finishes • Workmanship • Packaging

10 11/20/2012

ASTM F 1667 – Dimensions and Tolerances

• Dimensions – Length – flat top or under head, from bottom of head to

tip. All others measured overall. – Diameter – measured away from the gripper marks.

Deformed shank nails before the deformation.

• Length tolerance – 1 < L ≤ 2.5, ± 1/16 in. (±1.6 mm) – 2.5 < L ≤ 7, ± 3/32 in. (±2.4 mm)

• Head diameter tolerance – Hand-drive: ±10% – Mechanical-drive: comply with manufacturer specs and

function in tool.

11 11/20/2012

ASTM F 1667 – Physical and Mechanical Properties

• Recommends cold-bending ductility for low and medium carbon fasteners.

• Bending Yield Strength (Fyb) from Table S1.1 - Used in yield limit equations for calculation of lateral resistance (shear).

Nominal Diameter

(in.)

Bending yield (psi)

Bending yield (MPa)

O86-09 Bending

yielda (MPa)

0.099 ≤ 0.142

100,000 689 674-620

0.143< d ≤ 0.177

90,000 620 620-575

0.177 < d ≤0.254

80,000 552 575-478

0.254 < d ≤ 0.273

70,000 483 478-454

12 11/20/2012

aO86-09, §10.9.4.2: fy=50(16-dF) MPa

Nail Size

Type Dimension Pennyweight

8d 10d 16d

Common L 2-1/2 3 3-1/2

D 0.131 0.148 0.162

H 0.266 0.312 0.344

Box L 2-1/2 3 3-1/2

D 0.113 0.128 0.135

H 0.297 0.312 0.344

Sinker L 2-3/8 2-7/8 3-1/4

D 0.113 0.120 0.148

H 0.266 0.281 0.344 13 11/20/2012

Steel Wire Nails – “Commons”

NBCC Table

9.23.3.4/5

O86-09 Table A.10.9.5.2

ASTM F-1667 Table 15

Length (in.)

Diameter (mm/in.)

Common nail

Length (in.)

Diameter (in.)

101 4 4.88/0.192 20d 4 0.192

82 3-1/4 3.66/0.144 12d 3-1/4 0.148

76 3 3.66/0.144 10d 3 0.148

63 2-1/2 3.25/0.128 8d 2-1/2 0.131

57 2-1/4 2.95/0.116 7d 2-1/4 0.113

51 2 2.84/0.112 6d 2 0.113

(16d common: 3-1/2 , 0.162)

14 11/20/2012

Spécifications des Clous (T-NAILGUIDEC03)

15 11/20/2012

Hand-driven Nails v. Power-driven Nails

• Materials are same basic low carbon steel wire.

• Bending yield (fy) meet same minimum averages in ASTM F 1667 and the fy calculation in O86-09 does not differentiate by drive method.

• Geometry variations in length, head, and shank to accommodate tool characteristics.

• Same corrosion resistance required.

• Power-driven nails for metal hardware maybe hardened or partially hardened.

16 11/20/2012

Power-driven Nails with Connectors (T-PNEUMATIC12)

17 11/20/2012

Nail Specification

• Specify nail completely (length and diameter) not just penny weight. Examples, – An “8d common” specification means 2-1/2 in. length by 0.131

in. shank diameter with a full round head. – An “8d” specification is only length, 2-1/2 in. and does not

specify shank diameter or head diameter. – A “10d” specification for a connection with WSP side member

(7/16-in. [11 mm], Ge=0.50) and DFL main (G=0.50) could result in, • 10d common (3x0.148, 76x3.76), ZNDS=87 lb, Yw=10.6 N/mm • 10d box (3x0.128, 76x3.25), ZNDS=70 lb, Yw=9.4 N/mm • 10d sinker (3x0.120, 76x3.05) with sinker head, ZNDS=63 lb, Yw=8.9

N/mm • any nail that is 3 inches in length, unknown lateral and withdrawal

resistance.

18 11/20/2012

Job-Site Inspection Issues - Nails

• Alternate fastener meets or exceeds specified fastener and has been approved by the EOR or designer.

• Fasteners in compliance with ASTM F 1667 meet or exceed the minimum calculated fy for 0.099 to 0.177 in. (2.51-4.50 mm) diameters and for diameters greater than 0.254 in. (6.45 mm).

• Alternate fastener length meets minimum standard for NBCC, Section 9.23.3.2; not less than half of the length penetrates into side member, and for prescriptive framing, fastener meets the minimum size.

• Common nails from ASTM F 1667 will work as alternates to B111 nails for prescriptive and engineered construction.

19 11/20/2012

Screws in Wood Frame Construction

• NBCC, Table 9.23.3.5 permits the use of wood screws for subfloor fastening (diameter ≥ 3.2 mm); lumber and WSP.

• Applications that require qualified screw products: – Hanger and connector fastening;

– Shear walls;

– Diaphragm fastening other than subfloor;

– Substitution for lag screws.

20 11/20/2012

Screw Properties

• Most steel wood screws are case hardened so that they have torsional strength for driving.

• Installation torque is affected by screw design. • Head design plays a role in installation and installed

performance. • Corrosion resistance is by either mechanical

galvanization in combination with a finish coat or multiple barrier coatings. Stainless steel screws are available.

• Published proprietary engineering properties based on testing and calculation.

21 11/20/2012

Wood Screws in O86-09

Characteristics Size (gauge number)

6 8 10 12

ds, mm (in.) 3.50 (0.138) 4.16 (0.163) 4.82 (0.190) 5.48 (0.216)

dR, mm (in.) 2.87 (0.113) 3.33 (0.131) 3.86 (0.152) 4.34 (0.171)

Min fy, MPa ( ksi) 690 (100) 620 (90) 550 (80) 550 (80)

22 11/20/2012

Loading Specific Gravity

0.50 ≤ G ≤ 0.60 G > 0.60

Lateral 0.85ds ds

Withdrawal 0.7dR 0.9dR

Wood screw characteristics, Table 10.11.1

Lead hole requirements, Table 10.11.2.1

Lag Screws in O86-09

• Requires two-step lead hole.

• Shank lead hole – diameter and length to match lag screw.

• Threaded lead hole – at least length of threaded shank. – dense hardwoods, diameter 65 to 85% of shank

diameter;

– DFL 60 to 75% of shank diameter;

– Less dense species 40 to 70% of shank diameter.

11/20/2012 23

Self-drilling Screws

Self-drilling screws can be used as replacements for lag screws and wood screws and can also be used as alternates to nails in some applications. Self-drilling wood screws do not comply with ASME 18.2.1 for lags screws or ASME 18.6.1 for wood screws.

24 11/20/2012

Self-drilling Screws

• Head styles

• Threads

• Point style

25 11/20/2012

(C-FS11, p. 15) Type 17 point

Self-drilling Screws - Advantages

• Installation efficient because predrilling is seldom needed.

• Available in bulk and collated.

• Particularly good for subfloor fastening (better composite action than nailing and no squeaks).

• When installing, the installer can tell if the framing has been penetrated.

11/20/2012 26

QDPRO250G2

Connecting Wood to Metal

Pilot point – length needs to be at least thickness of wood side member plus thickness of metal main member.

Drill point with wings – drill point plunges through wood side member and wings break off when they enter the metal main member.

Both tips prevent wood side member from “climbing” the screw during installation.

27 11/20/2012

(C-FS11, p. 16)

Special Issues in Contemporary Wood Frame Fastening

28 11/20/2012

Corrosion Effects of Preservative Treatment Chemicals and Corrosion Resistance of Fasteners

• NBCC, §9.23.2.2 and O86-09, §4.3.4.2 require treatment for wood members in contact with masonry or concrete and where deterioration is likely.

• NBCC offers no specific corrosion resistance specification for fasteners in contact with chemically treated wood.

• For small diameter fasteners in contact with preservative treated wood, I-codes require HDG per ASTM A 153 or non-corrosive base metal, such as, stainless steel, silicon bronze, or copper. Some exceptions in IRC permit mechanical galvanization per ASTM B 695, Class 55.

29 11/20/2012

Evaluating Corrosion Resistance

• Salt spray testing (ASTM B117) and cyclic salt spray testing (ASTM G85).

• Direct correlation to corrosion performance natural environment not assured.

• ASTM G198-11 is for relative corrosion performance of driven fasteners in contact with treated wood.

• ICC-ES AC257 is for corrosion effects of treatment chemicals and corrosion resistance of fasteners.

30 11/20/2012

AC257 Corrosion resistance ratings: 1 – limited, treated wood in dry service 2 – limited use, untreated wood, salt exposure 3 – general use, treated wood, no salt exposure 4 – unrestricted use

Corrosion Effects of Treatment Chemicals and Corrosion Resistance of Fasteners

• For I-codes, corrosion resistance evidence of alternates to HDG by evaluation report based on AC257.

• ACQ represents a family of widely used formulations for wood preservative treatment.

• Coupon testing showed ACQ-D produces the most corrosive environment for carbon steel fasteners.

31 11/20/2012

Corrosion Effects of Treatment Chemicals and Corrosion Resistance of Fasteners

11/20/2012

(C-FS11, p. 11)

Stainless Steels for Fasteners

• ASTM A 493 – 09, Standard Specification for Stainless Steel Wire and Wire Rods for Cold Heading and Cold Forging.

• Type 304 stainless and Type 305 stainless (S30400, S30403, S30430 and S30500). Differentiated by Cr and Ni contents.

• Type 316 Stainless (S31600, S31603). Most corrosion resistant. Molybdenum (Mo) content.

• Type 410 stainless (S41000). Can be hardened.

33 11/20/2012

Performance of Stainless Steel Nails

• O86-09 is silent on the effect of material for nails with respect to withdrawal and shear.

• Shear addressed through fy (diameter basis). • Withdrawal has some unstated assumptions regarding coefficient of

friction. • Withdrawal per O86-09, Section 10.9.5.2 (based on McLain 1997)

Prw = φYwLpnfJAJB

φ = 0.6 resistance factor Yw=16.4df

0.82G2.2 (16.4 is the product of multiple adjustment factors and regression constant)

Lp=length of penetration nf= number of fasteners JA=Toe-nail factor JB=clinching factor

34 11/20/2012

Stainless Steel Nails - Withdrawal Performance Nail Diameter SG Measured PFPL DO86 M/D M/P

mm N/mm N/mm N/mm

smooth 2.77 0.37 8.48 10.97 2.55 3.3 0.77

2.77 0.49 17.34 21.59 4.62 3.8 0.80

2.77 0.55 22.87 29.56 6.09 3.8 0.77

3.38 0.37 11.19 13.39 3.00 3.7 0.84

3.38 0.49 21.70 26.34 5.44 4.0 0.82

3.38 0.49 19.91 26.34 5.44 3.7 0.76

3.38 0.49 22.19 26.34 5.44 4.1 0.84

3.38 0.55 23.96 36.07 7.17 3.3 0.66

4.19 0.37 12.35 16.60 3.57 3.5 0.74

4.19 0.49 21.78 32.65 6.48 3.4 0.67

4.19 0.55 24.25 44.72 8.55 2.8 0.54

Annular 3.38 0.49 59.10 26.34 5.44 10.9 2.24

• M/P ~ 0.75 • M/D ~ 3.6 • Based on M/P ratio, M/D

should be about 4.5

Date from: USFS, FPL, Techline, August 2012.

35 11/20/2012

SPECIFIC GRAVITY

• Specific gravity (dimensionless) is the ratio of the density of a material to the density of water.

• Used in the calculation of withdrawal and embedding strength for lateral resistance.

• For solid wood, use measured values (oven-dry basis).

• For SCL products, use equivalent specific gravity.

36 11/20/2012

SCL Families and Fastening

• Types of SCL products – PSL – parallel strand

lumber – OSL – Oriented strand

lumber – LSL – laminated strand

lumber – LVL – laminated

veneer lumber

• Directional with respect to fastening.

• SCL coordinates per ASTM D 5456.

37 11/20/2012

Equivalent Specific Gravity - SCL

• ASTM D 5456, Annex A2.1

• Withdrawal testing in Y-direction (X –direction if needed), using an 8d common nail (0.131x2-1/2 in.[3.33x63.5 mm]) minimum depth of penetration 1.25 in. (32 mm) includes the tip. Compare Pmax/5 to NDS 05, Table 11.2C (or calculate) to find equivalent performance, then G = Ge.

38 11/20/2012

Equivalent Specific Gravity – Wood Structural Panels, Face Withdrawal

Metric Type of panel

Wood Species - PLY Wood Species – OSB

SP DF Mixed Aspen SP

Ultimate load (lb/in)

835 730 641 550 648

Design load (lb/in) 167 146 128 110 130

Ge withdrawal (NDS)

0.55 0.52 0.49 0.45 0.49

Recommended Ge

Withdrawal 0.45

Notes: based on 23/32-in WSP, n>119, Design=Pmax/5, #10x12 (d=0.192 in.)

APA, TT-051C, 2011

39 11/20/2012

Equivalent Specific Gravity – SCL, Embedding Strength

Dowel bearing (embedding strength) tested using a dowel oriented in the Y-direction, and loaded in the L- and X-directions. Combine results from both directions. Five-percent offset value (P5%) is divided by the thickness of the bearing material and the diameter of the dowel. Results compared to table values to establish equivalent specific gravity.

5% off-set value for embedding strength.

40 11/20/2012

Equivalent Specific Gravity - SCL

Example from ICC-ES, ESR-1040 • Differs by product • Differs by fastener diameter (small and large)

41 11/20/2012

Cross-Laminated Timber (CLT)

11/20/2012 42

• Cross laminations of dimension lumber • Grade requirements per NGR No. 2 • Adhesives per CSA O112.10 • European experience with connection

design for CLT • FP Innovations providing leadership in

Canada

Cross-Laminated Timber (CLT) - Connections

11/20/2012 43

• CLT tends to resist splitting due to the effect of the cross laminations.

• Need to address some of the unique characteristics of CLT in connection design (e.g., unglued edges and gaps).

Splines and laps with screws

Connectors with screws and specialty nails

Self-drilling screws for end and angled fastening

Cross-Laminated Timber – Connection Design

11/20/2012 44

For more on CLT connections: 1. M. Mohammad, FP Innovations (2011) -

http://www.woodstructuressymposium.com/wp-content/uploads/2011/06/Mohammad_CLT_Connections.pdf

2. Uibel, T., and Blass, H.J. 2007. Edge joints with dowel type fasteners in cross laminated timber, CIB-W18/40-7-2. 11 pp.

3. Munoz, W., Mohammad, M., and Gagnon, S. 2010. Lateral and withdrawal resistance of typical CLT connections. WCTE 2010. 10 pp.

• Lap connections using self-drilling screws performed better than spine connections with normal wood screws (Munoz et al, 2010).

• Lateral capacity of connections with self-drilling screws is reasonably approximated by using the design equations from Uibel and Blass, O86 or Eurocode 5 provisions (Munoz et al, 2010).

• Withdrawal resistance functions for lag screws in O86 seem to be best estimators of characteristic values. Other functions tend to overestimate the characteristic value (Munoz et al, 2010).

Commitment to Environment

• Recycled material content

Structural connectors and mechanical anchors are made from a percentage of recycled steel; we purchase steel from multiple global suppliers, which makes it difficult to determine with certainty the exact amount of recycled content. The bulk of our steel comes from Oxygen Furnace Method.

• Recycling program in manufacturing

• Operations (lighting, VOCs)

45 11/20/2012

Adhesive Product Recycled Material Content

EDOT Adhesive 35.5%

ET-HP Anchoring Adhesive

16.0%

SET High Strength Anchoring Adhesive

4.5%

CIP Crack Injection Paste-over

21.0%

New Fastening and Connections from Simpson Strong-Tie

46 11/20/2012

Solutions for Specific Applications

• Metal Connector Fastening – SD Screws.

• SDWF with TUW for vertical load path.

• SDWC screws for plate-to-roof and stud-to-plate.

• SDWS and SDWH Screws for ledgers, multi-ply fastening and exterior foam.

• CLT connectors and fasteners.

47 11/20/2012

Metal Connector Fastening – SD screws

11/20/2012 48

SD9 and SD10 mechanically galvanized. SD8x125 not structural

11/20/2012 49

SDWF wood screw and Take-up Washer (TUW) designed to simplify vertical load path; TUW provides shrinkage compensation up to ¾ in. (19 mm) per floor.

SDWF with TUW

• Designed for vertical load path even with settlement and shrinkage.

• SDWF installed with ratcheting take-up washer keeps the system tight.

• Materials: SDWF carbon steel with Ecoat™; TUW 10 ga. galvanized steel.

• SDWF reported in ICC-ES ESR-3046; TUW reported in ICC-ES ESR-2320

50 11/20/2012

SDWC Wood Screws

• Vertical and lateral load path development.

• Top plate-to-roof framing (rafter or truss).

• Stud-to-plate connection over wood.

• Stud-to-plate connection over masonry or concrete.

• Materials: carbon steel, SDWC15600 clear zinc, SDWC15450 Ecoat™

51 11/20/2012

SDWC Wood Screws

• SDWC15600 reported in IAPMO-UES ER-262. SDWC15450 being added now.

• Evaluation report provides native values.

• See fliers for installation specific connections and design loads.

• For other installations, contact the Engineering Department (800-999-5099).

11/20/2012 52

11/20/2012 53

SDWC Screws – Plates-to-Roof Framing

11/20/2012 54

Installations are often complex because the screw passes through multiple materials and at different angles to the grain in each. Analysis and testing addresses these conditions. Design values based on the controlling performance or property.

55 11/20/2012

• For stud–to-plate over wood, use the SDWC15600.

• For stud-to-plate over masonry or concrete, use SDWC15450.

• SDWC has a special install guide tool and is black to differentiate.

• Published design tables for shear and uplift as needed for engineering design.

SDWS and SDWH Wood Screws (Reference: F-SDWSSDWH12C)

• Structural screws as alternate to lag screws

• Ledger attachment per Canadian flier

• Multi-ply fastening for trusses

• Furring strips through exterior foam

• See IAPMO-UES ER-192.

56 11/20/2012

SDWS and SDWH Screws

11/20/2012 57

FEATURES • Bold thread design provides

superior holding power. • Patented 4-cut tip reduces

installation torque and minimizes predrilling.

• Under-head nibs offer greater installation control when seating head.

• Large washer head provides maximum bearing area.

SDWS SDWH

11/20/2012 58

SDWS/SDWH/SDS as Substitutes for Lag Screws

• Three product lines of self-drilling structural wood screws (SDS, SDWS, SDWH) are suitable for typical wood-to-wood fastening commonly achieved with lag screws.

• Double barrier coating providing corrosion resistance equivalent to hot-dip galvanization .

• Options include screw products that meet or exceed the shear capacities of lag screws as calculated per CSA O86-09 (or NDS 05) as a one-for-one substitution.

– Recommendations are based on full penetration into the main member, which is considered to be six times the screw thread diameter (6D).

– The tip and threaded length in excess of 6D may protrude through the back of the main member without loss of shear capacity.

59 11/20/2012

CLT Connectors and Fasteners

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CNA4x60 ring-shank nail SD10212 screw

(Not shown ABR9020)

WSNTL Screws as Alternates to Nails in Shear Walls and Diaphragms

• Per ICC-ES ESR-1472, equivalent to 8d common and 10d common for shear walls (wind and seismic design

categories A and B) and diaphragms with sawn framing.

• Use the WSNTL screws in I-joist floors with no glue. Reduce allowable span by 12 in. (305 mm).

• Install standing up with Quik Drive® tools.

• Know if you penetrate the joist.

• No squeaks.

61 11/20/2012

Help on the Web

• For fastening help, go to www.strongtie.com

Click on Fastening Systems

http://www.strongtie.com/webapps/fastenerfinder/?source=fastenhp

http://www.strongtie.com/products/fasteners/index.html?source=qdnav

http://www.strongtie.com/literature/canada.html

62 11/20/2012

Summary

• ASTM F-1667 and common nails work as alternates to CSA B111 nail prescribed by NBCC, Section 9.23.

• Some significant issues to fastening in contemporary wood-frame construction: – Corrosion hazard created by treatment chemicals;

– Specific gravity of EWP;

– New EWP and hybrid systems.

• For more information about Simpson Strong-Tie fasteners and products, see www.strongtie.com.

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Q&A

Engineering Department, Simpson Strong-Tie Company Inc.

800-999-5099

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