Introducing the Design Guide for Nail-Laminated Timber

nailed it! introducing the design guide for nail-laminated timber

chicagoland tanyaluthi, p.e. march 7-8, workshops fast +epp 2018 Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board Copyright Materials

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© Fast + Epp 2018 “The Wood Products Council” is This course is registered with a Registered Provider with The AIA CES for continuing American Institute of Architects professional education. As Continuing Education Systems such, it does not include (AIA/CES), Provider #G516. content that may be deemed or construed to be an approval or Credit(s) earned on completion endorsement by the AIA of any of this course will be reported material of construction or any to AIA CES for AIA members. method or manner of handling, Certificates of Completion for using, distributing, or dealing in both AIA members and non-AIA any material or product. members are available upon ______request. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

AIA-registered provider Growing interest in mass timber has led to increased use not only of cross-laminated timber, but nail-laminated timber (NLT or nail-lam) — a lesser known but ostensibly more common material option. NLT is created by fastening pieces of dimension lumber, stacked on edge, into one structural element with nails or screws. It offers a unique aesthetic, flexibility of form, fast erection and a light carbon footprint — and is a cost-effective option for designers looking to expose wood structure. Using lessons learned from real projects, this workshop will provide practical strategies and guidance for the safe, predictable, and economical use of NLT. Discussion will include architectural and structural considerations, envelope and fabrication details, and key information from the Nail-Laminated Timber Design and Construction Guide , which was authored by the speakers.

workshop description 1. Review conceptual, planning and detailing considerations associated with NLT, including MEP, acoustics, and form variation. 2. Discuss engineering procedures for gravity and lateral design, including connection design, special loading conditions, and calculating fire resistance. 3. Study the design of NLT assemblies as building enclosure elements, while evaluating ways to mitigate heat, air and water flow into and out of the building. 4. Consider how NLT is prefabricated and installed, along with best practices for material procurement, tools and equipment, shipping, storage, and lifting.

learning objectives gravity 1 design lateral 2 design 3 connections odds & 4 ends overview gravity design 2x “joists” at 1-1/2 inches

choose: depth, profile species, grade

continuous vs. butt-jointed laminations

design approach gravity design NDS: CL, CF, Cr

Other: Klayup , Ksection

adjustment factors gravity design w

L LL wL 2/10

∆ = 0.0069wL 4/(EI) joint rules per IBC 2304.9.2.5 IBC 2304.9.3.3 NLT Guide Table 4.1 bending strength: 0.67 stiffness: layup factors based on 0.69 IBC Table 2306.1.4

Klayup gravity design w w

L L L

wL 2/8

∆ = wL 4/(185EI) ∆ = 5wL 4/(384EI) joint rules per IBC 2304.9.2.5 IBC 2304.9.3.3

bending strength: NLT Guide Table 4.1 0.202 (L/d) 1/4 / s 1/9 stiffness: layup factors based on 0.0436 (L/d) 9/10 / s 1/5 European research

Klayup Klayup

• 2x8 NLT • prefabricated with random staggered joints • clear span = 18 feet • 2-span continuous panels • nail spacing: two rows at 10 inches

L/d = 18 (12) / 7.25 = 29.8 s = 5”

design example Klayup

strength: . ./ K, / . stiffness: . ./ K, / .

reducing nail spacing to two rows at 5 inches revises K factors to 0.43 and 0.77, respectively

design example gravity design

d2 Ksection d1

X1 = X2 = 0.5

bending strength and stiffness: 3 X1 + X2 (d2/d1)

shear strength: X1

Ksection Ksection

d1 = 5.5” d d2 = 3.5” 2 d1 X1 = 1/3 X2 = 2/3

bending strength and stiffness: . K, ⁄ ⁄ ⁄. . shear strength:

K, .

design example gravity design NDS: Sections 3.2 –3.5 (Bending Members) Section 4.3 (Adjustment Factors) Supplement Tables 4A, 4B, 4C, 4F (Reference Design Values)

bending & shear bending strength • 2x8 NLT • prefabricated with random staggered joints

• span = 18 feet w • 2-span continuous panels 18’ 18’ • nail spacing: two rows at 10 inches • lumber: SPF No. 2 or better

Klayup,b = 0.39 (see previous example)

design example bending strength Loads

D: 25 psf NLT + plywood 20 psf floor finish 5 psf MEP allowance 50 psf total

L: 50 psf occupancy (office) 15 psf partition allowance 65 psf total

design example bending strength

Fb = 875 psi CF = 1.2 per NDS Supplement Table 4A Cr = 1.15

all other NDS factors = 1.0

Klayup, b = 0.39 per previous example

design example bending strength ASD strength checks (per foot width):

F′ , K,CCF 0.39 1.2 1.15 875 ≅

115 plf in in 18 ft x 12 12 ft ft M ≅ , 8

M 6M 656,000 lb in NG f ≅ S bd 12 in7.25 in design example bending strength Options?

• use higher grade lumber (Select Structural or MSR)

• increases F b • fabricate 3-span panels

• increases Klayup to 0.67 • use 18’ pieces (all laminations simple span)

• increases Klayup to 1.0 • use finger-jointed lumber

• increases Klayup to 1.0 • LRFD?

design example bending strength LRFD strength checks (per foot width):

1.2D + 1.6L governs (qu = 164 psf)

KF = 2.54 φ b = 0.85 per Appendix N λ = 0.8

design example bending strength

F′ , K, C C KϕλF 0.39 1.2 1.15 2.54 0.85 0.8 875 ≅

164 plf in in 18 ft x 12 12 ft ft M ≅ , 8

M 6M 680,000 lb in OK f ≅ S bd 12 in7.25 in

design example gravity design

floor vibrations gravity design NDS: Chapter 16 (Fire Design of Wood Members)

ASD Only w wbearing bearing,fire dfire

d achar

achar

dfire

achar achar fire design fire design • 2x8 NLT per previous examples • supported on 6-3/4” wide glulam beams • Type IIIA Construction • 1-hour rating required

effective char depth, achar = 1.8 in per NDS Table 16.2.1A

design example fire design Adjustment Factors for Fire Design per NDS Table 16.2.2:

• bending = 2.85 • bearing = ?? 2.03 is likely conservative

design example fire design Bending:

F′ , K, K C CF 0.39 2.85 1.2 1.15 875 ≅ ,

M ≅ 56,000 lb in per previous calculations

d 7.25 in 1.8 in 5.45 in

M 6M 656,000 lb in f ≅ , S bd 12 in5.45 in OK design example fire design Bearing at Interior Support:

w, 6.75 in 2 1.8 in 3.15 in

F′ , K C F 2.03 1.0 425 psi ≅

V 115 plf 18 ft ≅ 2,100 lbs (per foot width)

, f ≅ ≪ , . OK design example gravity 1 design lateral 2 design 3 connections odds & 4 ends overview lateral design SDPWS: Chapter 4 (Lateral Force-Resisting Systems) Tables 4.2A and 4.2B (Blocked Diaphragms)

diaphragms rigid vs. flexible diaphragms

B A

design example brace design forces (in kips) rigid diaphragms flexible diaphragms 32 29 14 36 61 68 97 34 74 41 65 90 120 43 95 61 110 100 160 52 110 77

AB C

design example lateral design sheathed on site

NLT joint NLT joint plywood joint plywood joint

panel joints ⊥ to panel joints ║ to NLT span NLT span diaphragms lateral design pre-sheathed panels

infill panel installed on site

typical high load diaphragms lateral design

potential load paths: perimeter beams steel straps NLT laminations

chords & collectors lateral design NDS: Sections 3.6-3.8 (Compression and Tension Members) Tables 4A, 4B, 4C, 4F (Reference Design Values) Section 4.3 (Adjustment Factors)

chords & collectors gravity 1 design lateral 2 design 3 connections odds & 4 ends overview connections

2015 IBC nailing requirements: §2304.9.3.2 min nail length = 2.5 * (blam) 2018 IBC nailing requirements: Table 2304.9.3.2 2 ¾”, 3”, 3 ½”, 4” nails 2x lams only

nailing patterns connections (nails in lamination beyond)

nail spacing (one row)

nail spacing (two rows)

nailing patterns connections

self-tapping screws connections

IBC toenailing requirements: §2304.9.3.2 feasible only for site-built NLT alternative means and methods: match lateral and withdrawal strength match lateral stiffness? other rational approaches connections to supports connections to supports 2015 NDS Reference Design Values

• 20D toenails (4” long, 0.192” Ø) @ 7” (max 4x nominal laminations, nails every other lam) • Withdrawal: Table 12.2C • Shear: Table 12N

For G = 0.42: Could also argue for lower values based on 33 ksi nail yield strength and/or nail W ≅ / spacing of 8” (4x actual laminations) Z ≅ / design example connections

connections to supports connections

shear transfer gravity 1 design lateral 2 design 3 connections odds & 4 ends overview odds & ends

hassembly

beffective = width of load + hassembly

point loads odds & ends

V V width of opening beyond cosθ

openings odds & ends

caution: detail to allow for swelling without tensile failure of screws cantilevers odds & ends

common “holes”: mockup requirements shop drawings (joint layouts) weather protection plan fabrication and erection tolerances sealers and finishes specs This concludes the American Institute of Architects Continuing Education Systems Course

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