Heavy Timber Trusses. Workshop: Exposed Connections in Timber Trusses and Structures: Designing for Beauty and Function

Transcription

1 Heavy Timber Trusses Workshop: Exposed Connections in Timber Trusses and Structures: Designing for Beauty and Function Presented by RL. Ben Brungraber, PhD, PE Fire Tower Engineered Timber Disclaimer: Presented This on [Date] presentation by [Author s Name] was developed by (Edit the Master Slide to change this text) a third party and is not funded by WoodWorks or the Softwood Lumber Board

2 Workshop Description In timber designs where the structure is an integral part of the architecture, detailing for trusses and member intersections can be particularly challenging. Presented by renowned timber specialists, this workshop will provide insight relevant to both engineers and architects on heavy timber trusses, glulam post and beam and mass timber component connections. Timber truss topics include an overview of heavy timber truss configurations, guidance on their applications and important design considerations. An introduction to modern timber connections will review guiding principles of mass timber connections, custom and prefabricated hardware, codes, and design considerations using project examples. Among topics included are methods for achieving fire resistance, design simplicity and construction efficiency.

3 Workshop: Learning Objectives At the end of this program, participants will be able to: 1. Review various heavy timber truss configurations, applications and important design considerations. 2. Discuss structural design, connection options and fabrication processes of timber trusses including insight on specifications and cost. 3. Explore modern glulam and mass timber connection solutions available including commodity, preengineered and custom designed connections. 4. Explore practical aspects of design such as fireresistance, design simplicity and construction efficiency.

4 Heavy Timber Trusses RL Ben Brungraber, PhD, PE Loading the trusses Ridge beams can halve load, etc. Analysis no pins and continuous members Eccentric Connections nearly unavoidable and often preferable Deflections connection slips and deformations are hard to include End Wall Trusses maddeningly common; can be worse than useless

5 Heavy Timber Truss Types: Pitched Top Chord (including curved top chord) Scissor (including curved bottom chord) Parallel Chords Miscellaneous/ Mongrel Including Collared Rafters Heavy Timber Truss Connections: Notches Plates (heavy/bolted and toothed/light) Rods and Fittings historic examples Machine Shop vs Welding Shop Steel tension members? Diagonals All-wood members? Tension perpendiculars Heavy Timber Truss Miscellany Lateral Bracing The Dark Art of Camber Top chord buckling (Bottom chord in load reversals) Simple alignment for seasoning in-situ timbers End wall drumming

6 How DO we Get Into Stuff? Me, circa 1973

7 A Truss Whisperer is Made

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9 Bigger Models; More Testing

10 A Fair Fight?

11 Bucknell Undergraduate Project 50 Pedestrian Bridge; c. 1981

12 Another Jump in Scale; 240 Pedestrian Bridge

13 Timber Framers Guild of North America; Guelph, ON 1992

14 Old School and New School Construction Techniques/Technologies

15 Pitched Top Chord Trusses Span < < Spacing < 20 1:6 < Slope < 1:16 1:5 < Span/Depth < 1:7 Specials: Curved Chord, Scissors, Rods

16 Simple Trusses The Quintessential Industrial Revolutionary Truss

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19 Diagonals onto King Post and at Roughly Roof Pitch

20 Traditional Truss Design/Analysis Write if you really NEED all of this

21 Corbel and/or Brace Support

22 Concealed, Starter Blocks Hardware at Chords Joint

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25 Everyone Ought to get a Chance at a Cathedral

26 Or, at least, a Church

27 A True King Post -Perhaps the Most Complex Timber Joint I Have Designed

28 What Can Happen, When a Client Calls Your Bluff?

29 All Wood Joinery

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31 Eccentricity in Heel Plates

32 Heavy Sawn Planks, Corbels, Pegs, & Light Screws

33 Diagonal Rods in 72 Spans

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35 Raising Choreography to Protect Tails

36 Grand Opening show in new Performing Arts Center

37 With 70 kips in Each Rod, Those are not Shear Bolts

38 Curved Top Chord Bowstring Trusses up to 250 spans 1:6 < span/depth <1:8 top chord radius roughly the span

39 Scissors Trusses

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41 The Scissors Crux Connection

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48 Clasping King Posts

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53 Scissors Trusses and Dimensions Change During Process

54 Concealing the Connectors can be a DRAG

55 Proud and Relieved Crew

56 At Foot of Grandfather Mountain, Boone, NC

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58 Curved Chords How to Fabricate Curves?

59 Trees, Generally, Grow Straight Pay Attention to This

60 Curved Chord Trusses

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64 Steam-bent; or CompWood

65 The GehryHall Winery Visitors Center

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67 Curve Issues : Bending, Radial Tension, and Straightening

68 And: How to Grab Curve Without Undue Damage?

69 King Post Gets a Crown and a Stirrup Turns Tension into Compression

70 Shear Keys Transfer Chord Forces at Eave Connections Longer Intersection between Members

71 Truss Analysis

72 So Basic; So Neglected from Hoyle, Design of Wood Structures

73 Which Member is the Support?

74 The King Rod/Post is Crucial Component

75 Options: Notch Top Plate/Chock Pinned Plate

76 Options: Straps Rod Support the Plate

77 What we seem to Wish

78 But this is More Realistic

79 Cross-Grain Prying Components The Actual Bolt Forces are Quite Complex, Indeed

80 Parallel Chord Trusses 1:8 < Span/Depth < 1:10 Diagonal Direction Matters, a Lot Least Efficient Layout; ignores M & V Added Arches Burr Trusses Town Lattice Truss-Girders

81 Parallel Chords

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86 Best Barn/Shop Ever. 40 x 50 Clear (Basement, too)

87 Cambering and Adjusting can be Simple, with Steel Rods

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89 Tension in Bottom Chord can be Minimal

90 Span/Depth = 1:5

91 FengShuiBad News

92 Tension Diagonals of Timber and Panel Length Varies

93 My Sole Split Ring Job

94 Compression Diagonals of Timber Note Diagonal-Free center panel

95 Tension Diagonals of Steel Note: Rod Angle Changes

96 Overly Sloped Rods Add Apparent Length

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98 The Golden Age of Heavy Timber Trusses for ALL of this

99 Industrial Revolution Trusses

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102 Industrial Revolution Ripoffs 2 Timbers & 3 Rods

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105 1 Timber, 2 Rods

106 Avoid Turnbuckles to Increase Capacity and Reduce Depth

107 One Timber and Both 1 and 2 Rods

108 A Barn Full of Fun

109 Context for Truss

110 Plumb Posts can get SO Boring, after a while

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112 This Might Just Be My Best Shot, Ever

113 Concealed Steel

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115 Celebrated Steel

116 It s ALL About the Hardware

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118 Hardware

119 We see this, and worse, all the time

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122 Notches

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127 Collared Rafters Raised Chord Trusses Collar Strut, Tie, or Beam? Failing Roofs for Centuries

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129 Fire, Ready, Aim

130 Slate Roof AND $70,000 worth of windows preinstalled

131 In Tension, Compression, or Minimal? It s All About the Supports

132 Collar Strut, Tie, or BEAM

133 Humans have been repairing these for n-2 years; Where: n = Number of Years ago the first ones were built

134 A Truss? Tied Eaves NO Compression Capacity

135 Curved/Collared?

136 Modeling the Connections; Blade to Rafters and Collar

137 Other Trusses Vierendeel Truss and/or Girder

138 (Ithiel, Architect) Town Lattice Trusses

139 Point Load at Support The Tough Spot

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142 Non-Trusses

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144 Lots of Elements AND My Stupidest Truss (so far)

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147 A Minor Dip in the Ridge is NOT Minor in a 1000 Ridge

148 Supporting a 1000 Wooden Balloon Using 150 Steel Needles

149 Previous Repair Splints but Still Looking Troubled, Back There

150 Just How Troubled IS it? 4 & 6 Heavy Planks, 180 Up

151 Would you drive a Suburban across this?

152 Maybe THIS Rig, and only very quickly