nailed it!introducing the design guide

for nail-laminated timber

chicagolandworkshops

tanyaluthi, p.e.fast +epp

march 7-8,2018

Disclaimer: This presentation was developed by a third party and is not

funded by WoodWorks or the Softwood Lumber Board

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© Fast + Epp 2018

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workshopdescription

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.

learningobjectives

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.

overview

odds &ends

gravitydesign

lateraldesign

connections

1

2

3

4

designapproach

gravitydesign

2x “joists”at 1-1/2 inches

choose:depth, profilespecies, grade

continuous vs. butt-jointedlaminations

adjustmentfactors

NDS:CL, CF, Cr

gravitydesign

Other:Klayup, Ksection

Klayup

gravitydesign

w

L L L

wL2/10

∆ = 0.0069wL4/(EI)

bending strength:

0.67

stiffness:

0.69

joint rules perIBC 2304.9.2.5IBC 2304.9.3.3

NLT Guide Table 4.1

layup factors based onIBC Table 2306.1.4

Klayup

gravitydesign

w

LL L

w

wL2/8

wL2/8

∆ = 5wL4/(384EI)∆ = wL4/(185EI)

bending strength:

0.202 (L/d)1/4 / s1/9

stiffness:

0.0436 (L/d)9/10 / s1/5

joint rules perIBC 2304.9.2.5IBC 2304.9.3.3

NLT Guide Table 4.1

layup factors based onEuropean research

designexample

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”

designexample

Klayup

strength:

K�����,� .�����.���/���/�� �. ��

stiffness:

K�����,� .������.���/����/ � �. !"

reducing nail spacing to two rows at 5 inches

revises K factors to 0.43 and 0.77, respectively

Ksection

gravitydesign

shear strength:

X1

bending strength and stiffness:

X1 + X2 (d2/d1)3

Ksection

X1 = X2 = 0.5

d1

d2

designexample

Ksection

d1 = 5.5”

d2 = 3.5”

X1 = 1/3

X2 = 2/3

bending strength and stiffness:

K#$%&'(),� * �⁄ , � �⁄ �.� �.�⁄ � �. -.

shear strength:

K#$%&'(),/ �. ��

d1

d2

bending& shear

NDS:Sections 3.2 – 3.5

(Bending Members)

Section 4.3 (Adjustment Factors)

Supplement Tables 4A, 4B, 4C, 4F (Reference Design Values)

gravitydesign

designexample

bendingstrength

• 2x8 NLT

• prefabricated with random staggered joints

• span = 18 feet

• 2-span continuous panels

• nail spacing: two rows at 10 inches

• lumber: SPF No. 2 or better

Klayup,b = 0.39 (see previous example)

18’ 18’

w

designexample

bendingstrength

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

designexample

bendingstrength

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

designexample

bendingstrength

ASD strength checks (per foot width):

F′�,234 K�����,�C6C7F� 0.39 1.2 1.15 875 ≅ A"�BCD

M

115plf12 inft

L 18ftx12 inft�

8 ≅ -!, ���NODP

f� MS 6M

bd� 6�56,000lbin�12in�7.25in�� ≅ -��BCD U A"�BCD NG

designexample

bendingstrength

Options?

• use higher grade lumber (Select Structural or MSR)• increases Fb

• 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?

designexample

bendingstrength

LRFD strength checks (per foot width):

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

KF = 2.54

φb = 0.85 per Appendix N

λ = 0.8

designexample

bendingstrength

F′�,234 K�����,�C6C7K6ϕ�λF� 0.39 1.2 1.15 2.54 0.85 0.8 875 ≅ Y.�BCD

M

164plf12 inft

L 18ftx12 inft�

8 ≅ Y�, ���NODP

f� MS 6M

bd� 6�80,000lbin�12in�7.25in�� ≅ "!�BCD Z Y.�BCD OK

floorvibrations

gravitydesign

firedesign

gravitydesign

NDS:Chapter 16

(Fire Design of Wood Members)

ASD Only

achar

achar

achar

achar

dfire

dfire

d

wbearing,firewbearing

designexample

firedesign

• 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

designexample

firedesign

Adjustment Factors for Fire Design

per NDS Table 16.2.2:

• bending = 2.85

• bearing = ?? 2.03 is likely conservative

designexample

firedesign

Bending:

F′�,234 K�����,�K['7$C6C7F� 0.39 2.85 1.2 1.15 875 ≅ ., ���BCD

M ≅ 56,000lbin per previous calculations

d['7$ 7.25in \ 1.8in 5.45in

f� MS 6M

bd� 6�56,000lbin�12in�5.45in�� ≅ �A�BCD Z ., ���BCD

OK

designexample

firedesign

Bearing at Interior Support:

w�$�7')^,['7$ 6.75in \ 2 1.8in 3.15in

F′%_,234 K['7$C�F%_ 2.03 1.0 425psi ≅ Y!�BCD

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

f%_ bc

b��defghijk,lihf�

�,*��#*�')��.*�')� ≅ -!BCD ≪ Y!�BCD

OK

overview

odds & ends

gravitydesign

lateraldesign

connections

1

2

3

4

diaphragms

lateraldesign

SDPWS:Chapter 4

(Lateral Force-Resisting Systems)

Tables 4.2A and 4.2B(Blocked Diaphragms)

designexample

rigid vs. flexiblediaphragms

A

B

C

designexample

brace design forces(in kips)

3214

6134

6543

11052

A B C

rigid diaphragmsflexible diaphragms

2936

6874

9095

100110

9741

12061

16077

diaphragms

lateraldesign

sheathed on site

plywood jointNLT joint

NLT joint

plywood joint

panel joints ⊥ to NLT span

panel joints ║ to NLT span

diaphragms

lateraldesign

pre-sheathed panels

typical high load

infill panel installed on site

chords &collectors

lateraldesign

potential load paths:perimeter beamssteel straps

NLT laminations

chords &collectors

lateraldesign

NDS:Sections 3.6-3.8

(Compression andTension Members)

Tables 4A, 4B, 4C, 4F (Reference Design Values)

Section 4.3 (Adjustment Factors)

overview

odds &ends

gravitydesign

lateraldesign

connections

1

2

3

4

nailingpatterns

connections

2015 IBC nailing requirements:§2304.9.3.2 min nail length = 2.5 * (blam)

2018 IBC nailing requirements:Table 2304.9.3.22 ¾”, 3”, 3 ½”, 4” nails

2x lams only

nailingpatterns

connections

nail spacing(two rows)

nail spacing(one row)

(nails in lamination beyond)

self-tappingscrews

connections

self-tappingscrews

connections

connections tosupports

connections

IBC toenailing requirements:§2304.9.3.2 feasible only for site-built NLT

alternative means and methods:match lateral and withdrawal strengthmatch lateral stiffness?

other rational approaches

designexample

connectionsto 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:

W ≅ "oNO/pqZ ≅ o��NOC/pq

Could also argue for lower values based on 33 ksi nail yield strength and/or nail spacing of 8” (4x actual laminations)

connections tosupports

connections

connections tosupports

connections

sheartransfer

connections

overview

odds &ends

gravitydesign

lateraldesign

connections

1

2

3

4

pointloads

odds &ends

hassembly

beffective = width of load + hassembly

openings

odds &ends

V��scosθ

V��s

θ

width of opening beyond

openings

odds &ends

openings

odds &ends

cantilevers

odds &ends

caution:detail to allow for swellingwithout tensile failure of screws

specs

odds &ends

common “holes”:mockup requirements

shop drawings (joint layouts)

weather protection plan

fabrication and erection tolerances

sealers and finishes

thankyou

This concludes the American Institute of Architects

Continuing Education Systems Course

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