Box Beams ARCH 544 Wood Structures Trevor Chou Ryan Lawson - - PowerPoint PPT Presentation

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Box Beams ARCH 544 Wood Structures Trevor Chou Ryan Lawson - - PowerPoint PPT Presentation

Jan 25, 2023 682 likes •1.03k views

Box Beams ARCH 544 Wood Structures Trevor Chou Ryan Lawson Background Box Beam Structure Dimension Lumber for top & bottom flanges & stiffeners Structural panels for webs Panel joints offset for optimal continuity

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SLIDE 1

Box Beams

ARCH 544 – Wood Structures Trevor Chou Ryan Lawson

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SLIDE 2

Background

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SLIDE 3

Box Beam Structure

  • Dimension Lumber for top &

bottom flanges & stiffeners

  • Structural panels for webs
  • Panel joints offset for optimal

continuity of beam webs

  • Stiffeners act as shear splices

for panel joints & resist web buckling

  • Should be spaced no more than 4

ft apart

Source: “Data File: Nailed Structural-Use Panel and Lumber Beams Z416.” APA Wood, APA - The Engineered Wood Association, Feb. 2009, www.apawood.org/publication- search?q=Z416&tid=1.

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SLIDE 4

Advantages of Box Beams

  • Longer spans than dimension lumber
  • High strength and stiffness
  • No shrinkage, warping, or twisting
  • Light weight
  • Easy to fabricate
  • Constructed of readily available materials
  • Open interior allows for insulation

Source: “Data File: Nailed Structural-Use Panel and Lumber Beams Z416.” APA Wood, APA - The Engineered Wood Association, Feb. 2009, www.apawood.org/publication- search?q=Z416&tid=1.

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SLIDE 5

Standard Box Beams

  • Tables available for sizing

beams

  • Give allowable loads in lbs/ft
  • Multiple lumber sections

can be used for flanges to increase flexural capacity

  • Thicker panel sizes provide

higher shear capacities

Source: “Data File: Nailed Structural-Use Panel and Lumber Beams Z416.” APA Wood, APA - The Engineered Wood Association, Feb. 2009, www.apawood.org/publication- search?q=Z416&tid=1.

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SLIDE 6

Box Beam Design

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SLIDE 7

Design Specifications

  • NDS for Wood Construction
  • Panel Design Specification

(D510)

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SLIDE 8

Connection Design

  • NDS Section 12 – Dowel Type Fasteners
  • Withdrawal Design
  • Lateral Design
  • Critical for Box Beam Design
  • Capacity taken as lowest value of all possible yield modes from

Table 12.3.1A

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SLIDE 9

Connection Design: Lateral Design Values

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 10

Connection Design: Yield Modes

Single Shear Connections Double Shear Connections

Source: Koch, Lori, and Adam Robertson. “Connection Design Examples Using the 2015 NDS (DES345).” American Wood Council, American Wood Council, www.awc.org/education/main/lists/des-design-considerations/des345-2015-nds-connection-primer.

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SLIDE 11

Connection Design: Lateral Design Terms

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 12

Connection Design: Nail Dimensions

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 13

Connection Design: Rd

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 14

Connection Design: Fem

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 15

Connection Design: Fes

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 16

Connection Design: Fyb

  • Dowel Bending Yield Strength
  • Determined per Section 12.3.6
  • Taken as 100,000 psi

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 17

Connection Design: Lateral Design Value Tables

Source: NDS: National Design Specification for Wood Construction. American Wood Council, 2018.

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SLIDE 18

Connection Design Calcs

  • : (Single Shear)
  • Mode IM = 299 lbs
  • Mode IS = 50 lbs
  • Mode II = 102 lbs
  • Mode IIIM = 111 lbs
  • Mode IIIS = 58 lbs
  • Mode IVM = 82 lbs

Controls

Sources:

  • Koch, Lori, and Adam Robertson. “Connection Design Examples Using the 2015 NDS (DES345).” American Wood Council, American Wood Council, www.awc.org/education/main/lists/des-design-considerations/des345-2015-nds-connection-primer.
  • NDS: National Design Specification for Wood Construction. American Wood Council, 2018.
  • “Panel Design Specification D510.” APA Wood, APA - The Engineered Wood Association, May 2012, www.apawood.org/publication-search?q=D510&tid=1.
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SLIDE 19

Mechanics of Materials: Nails

  • Allowable Load for Nail Shear:
  • Sources:
  • NDS: National Design Specification for Wood Construction. American Wood Council, 2018.
  • “Technical Topics: Nailed Box Beam Design Example TT-116.” APA Wood, APA - The Engineered Wood Association, 20 Nov. 2014, www.apawood.org/publication-search?q=tt116.
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SLIDE 20

Mechanics of Materials: Bending

  • Moment of Inertia:
  • Allowable Load for Bending:
  • Sources:
  • NDS: National Design Specification for Wood Construction. American Wood Council, 2018.
  • “Technical Topics: Nailed Box Beam Design Example TT-116.” APA Wood, APA - The Engineered Wood Association, 20 Nov. 2014, www.apawood.org/publication-search?q=tt116.
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SLIDE 21

Mechanics of Materials: Bending

  • Allowable tension stress, ft, should be used in bending equation:
  • Bottom chord is in pure tension, and allowable tension stresses

control over allowable compression stresses.

  • Sources:
  • NDS: National Design Specification for Wood Construction. American Wood Council, 2018.
  • “Technical Topics: Nailed Box Beam Design Example TT-116.” APA Wood, APA - The Engineered Wood Association, 20 Nov. 2014, www.apawood.org/publication-search?q=tt116.
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Mechanics of Materials: Web Shear

  • First Moment of Area:
  • 𝑅 = 𝑐𝑢
  • −
  • 𝑅 = 𝑢
  • =
  • 𝑅 = 𝑅 + 𝑅
  • Allowable Load for Web Shear:
  • Sources:
  • NDS: National Design Specification for Wood Construction. American Wood Council, 2018.
  • “Panel Design Specification D510.” APA Wood, APA - The Engineered Wood Association, May 2012, www.apawood.org/publication-search?q=D510&tid=1.
  • “Technical Topics: Nailed Box Beam Design Example TT-116.” APA Wood, APA - The Engineered Wood Association, 20 Nov. 2014, www.apawood.org/publication-search?q=tt116.
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Box Beam Allowable Load:

  • Bending:

Pmax = 2185 lbs

  • Web Shear:

Pmax = 2305 lbs

  • Nail Shear:

Pmax = 2383 lbs Bending Controls

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SLIDE 24

Testing

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SLIDE 25

Box Beam Construction

Sources: “Data File: Nailed Structural-Use Panel and Lumber Beams Z416.” APA Wood, APA - The Engineered Wood Association, Feb. 2009, www.apawood.org/publication- search?q=Z416&tid=1.

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Test Set Up

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SLIDE 27

Test Set Up

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Testing

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Results

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Results

1000 2000 3000 4000 5000 6000 7000 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Load, P (lbs) Midspan Deflection, Δ (in)

Load vs Deflection of Box Beam Load Test

Deflection (in) Load (lbs) 1/16 750 3/16 1000 4/16 2000 6/16 2750 8/16 3000 9/16 3750 10/16 4000 12/16 4250 13/16 4750 14/16 5000 15/16 5225 24/16 5500

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Results

  • Failed due to Shear Buckling in the Webs followed by crushing of the

structural panel at nail connections and disconnect of the structural panel from the nails

  • Allowable design calculations showed bending to control
  • Discrepancies likely lie in the inherent uncertainty in material properties
  • Failure occurred at 4000 lbs (point at which popping first occurred)
  • Test continued to 5500 lbs to visually see failure mode
  • Safety Factor:
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SLIDE 32

Thank You!

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SLIDE 33

Sources

  • “Data File: Nailed Structural-Use Panel and Lumber Beams Z416.” APA Wood, APA - The

Engineered Wood Association, Feb. 2009, www.apawood.org/publication- search?q=Z416&tid=1.

  • Koch, Lori, and Adam Robertson. “Connection Design Examples Using the 2015 NDS

(DES345).” American Wood Council, American Wood Council, www.awc.org/education/main/lists/des-design-considerations/des345-2015-nds- connection-primer.

  • NDS: National Design Specification for Wood Construction. American Wood Council,

2018.

  • “Panel Design Specification D510.” APA Wood, APA - The Engineered Wood Association,

May 2012, www.apawood.org/publication-search?q=D510&tid=1.

  • “Technical Topics: Nailed Box Beam Design Example TT-116.” APA Wood, APA - The

Engineered Wood Association, 20 Nov. 2014, www.apawood.org/publication- search?q=tt116.