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1
External Post-Tensioning
Extends Load Carrying Life of
Wood Bowstring Trusses
By: Steven G. Provenghi, PE, SE, SECB
Mackintosh & Mackintosh, Inc.
Consulting Structural Engineers© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
(Photographs Courtesy of David W. Cocke, SE; Structural Focus)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Common TrussesUsed in Building Construction
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Timber and Construction HandbookTimber Engineering Company; 1956
2
Comparison ofAxial Stresses
Timber and Construction HandbookTimber Engineering Company; 1956
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
3
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
4
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(Standard Mackintosh Truss Plans)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDExample of Original Graphical Methods of Analysis
5
Most Common Commercial Bowstring Truss Manufacturers In
California• Arch-Rib Truss Co. Ltd. (Multi-Member Chord)
• Summerbell Roof Structures (Multi-Member & Mono-chord)
• Vo-Vec Roof Structures (Multi-Member Chord)
• Commercial Roof Structures (Multi-Member Chord)
• National Truss Company (Multi-Member Chord)
• Easybow Trusses by U. S. Structures (Mono-chord)
• Mack Truss by Mackintosh & Mackintosh, Inc (Mono-chord)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Typical Truss Profile
for
Arch-Rib Trusses•Multi-Member Chords
•Segmental Upper Chord
•Inside Shoes at Heels in earliest trusses
•Outside Shoes at Heels in Later Construction
•Inside Shoes Tended to cause Splitting in Lower Chords at Heel Connection
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(1941 Arch-Rib Truss Design Manual)
Typical
Truss Profiles
for
Summerbell Roof Trusses
M l i M b h d• Multi-Member chords
•Upper chords of nail laminated construction
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Circa 1930’s Summerbell Design Manual)
6
Standard Summerbell
Upper Chord Sections
of Nail Laminated Construction
•Used when rafters were specified to be supported by hangers
•Also specified when rafters installed above and lapped over upper chord
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Circa 1930’s Summerbell Design Manual)
Standard Summerbell
Upper Chord Section
with Ledger Lamination
• Used when rafters specified to rest on ledgerspecified to rest on ledger
•Small block used to tie rafters together above upper chord
•Primary cause of web-pullout and upper chord buckling
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Circa 1930’s Summerbell Design Manual)
Nail Laminated Upper Chord
Common Nailing 16d and 30d for 2x laminations
30d and 50d for 3x laminations
Used in Summerbell Roof Trusses and Easybow Roof Trusses
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(Timber Design and Construction Manual; 1956)
7
Standard Segmental Bowstring Roof Trusses
Designed by Mackintosh & Mackintosh, Inc.
Used by: Vo-Vec Roof Structures
Commercial Roof Structures
National Truss
● Multi-member chords ● Split shoes and heels
● Segmental upper chord construction ● STILL USED TODAY
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Typical Multi-Member Segmental Band-Sawed
Upper Chord Construction
Used in Arch-Rib, Vo-Vec, Commercial and National Roof Truss Construction
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Easybow Truss
by
U.S. Structures
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
• Webs are Radial• Mono-chord Construction• Used Nail Laminated Upper
Chords & Glu-laminated Timber
8
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDExample of Easy Bow Truss
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Easy Bow Truss Web Connection
Mack TrussMono-Chord Truss Construction
designed by Mackintosh & Mackintosh, Inc.
Used in Trusses fabricated by Vo-Vec Roof Structures, Commercial Roof Structures and National Roof Structures
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
9
Why Do Bowstring Trusses Fail?
Recent testing has shown that the allowable tensiletensile stresses in timber used in the original design of these trusses was too high. g g
1955 stresses 1997 stressesFt = 1450 psi Ft = 675 psiFb = 1450 psi Fb = 1000 psi
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(Western Wood Products Association)© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Western Wood Products Association)
10
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Western Wood Products Association)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Western Wood Products Association)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Western Wood Products Association)
11
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED(Western Wood Products Association)
Why Do Bowstring Trusses Fail? (cont)
• Cross grain shrinkage of timber attached with steel side plates with multiple rows of bolts often causes the initial splitting.p g
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Cross Grain Shrinkage© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
12
Why Do Bowstring Trusses Fail ?(cont)
• Cross grain shrinkage of timber attached with steel side plates with multiple rows of bolts often causes the initial splitting.p g
• Timber defects (Large knots)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Timber Defect© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
Why Do Bowstring Trusses Fail ? (cont)
• Cross grain shrinkage of timber attached with steel side plates with multiple rows of bolts often causes the initial splitting.p g
• Timber defects (Large knots)• Bolts in a row
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
13
Example of Bolts In A Row© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
Why Do Bowstring Trusses Fail? (cont)
• Excess Loading– Gravity– Mechanical EquipmentMechanical Equipment– Multiple layers of roofing
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Roof Mounted Equipment © 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
14
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Suspended Racks© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
Excessive Roofing © 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
15
Why Do Bowstring Trusses Fail?(cont)
• Excess Loading– Gravity– Mechanical EquipmentMechanical Equipment– Multiple layers of roofing
• Stability problems associated with upper chord
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Upper Chord Buckling(Photo Courtesy of SPS, Inc.)
Upper Chord Repair with Out-of-Plane Braces(Photo Courtesy of SPS, Inc.)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
16
(Photo Courtesy of Jerry Erstad, SE; Erstad Engineering)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Buckling
(Photo Courtesy of Jerry Erstad, SE; Erstad Engineering)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Buckling
(Photo Courtesy of Jerry Erstad, SE; Erstad Engineering)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Upper Chord Repair with Lateral Bracing
17
Why Do Bowstring Trusses Fail? (cont)
• Stability problems associated with upper chord
• Earthquake induced loadsEarthquake induced loads
The Most Common Failures in Bowstring Roof Trusses
• Splitting of Lower Chord along Bolt Lines at Steel Splice Plates and Heel Plates
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Splitting caused by Cross Grain Timber Shrinkage in Lower Chord© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
18
Example of Splitting Along Splice Connection© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
Example of Splitting Along Splice Connection
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Splitting Along Splice Connection© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
19
The Most Common Failures in Bowstring Roof Trusses (cont)
• Splitting of Lower Chord along Bolt Lines at Steel Splice Plates and Heel Plates
• Tension Failure in Lower ChordTension Failure in Lower Chord
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Lower Chord Tension Failure
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDLower Chord Tension Failure
20
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Lower Chord Tension Failure
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Lower Chord Tension Failure
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDLower Chord Failure
21
The Most Common Failures in Bowstring Roof Trusses (cont)
• Splitting of Lower Chord along Bolt Lines at Steel Splice Plates and Heel Plates
• Tension Failure in Lower ChordTension Failure in Lower Chord• Web Splitting and Web Pull-Out
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDWeb Pullout Due To Improper End Distance
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDWeb Pullout Due To Improper End Distance
22
The Most Common Failures in Bowstring Roof Trusses (cont)
• Splitting of Lower Chord along Bolt Lines at Steel Splice Plates and Heel Plates
• Tension Failure in Lower ChordTension Failure in Lower Chord• Web Splitting and Web Pull-Out• Upper Chord Splitting
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Upper Chord Splitting© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Rib Replacement
23
(Photo Courtesy of Jerry Erstad, SE; Erstad Engineering)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Splitting
The Most Common Failures in Bowstring Roof Trusses (cont)
• Splitting of Lower Chord along Bolt Lines at Steel Splice Plates and Heel Plates
• Tension Failure in Lower ChordTension Failure in Lower Chord• Web Splitting and Web Pull-Out• Upper Chord Splitting• Upper Chord Buckling
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDUpper Chord Buckling
24
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDUpper Chord Buckling
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDWeb Failure
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Repair
25
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDCompleted Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Repair with Web Connection Strengthening
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDCompleted Truss Repair
26
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDCompleted Truss Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Buckling
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDCompleted Repair
27
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDCompleted Repair
Instances where upper
chord instability ycan occur
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(1941 Arch-Rib Truss Manual)
(Photograph Courtesy of David W. Cocke, SE; Structural Focus)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Stability Bracing Missing
28
Photo Courtesy of David W. Cocke, SE; Structural Focus)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDMonitor Opening with No Upper Chord Bracing
Truss Repair Procedure
• Shore truss up to restore original truss geometry and to remove stress from truss members.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Truss Shoring
29
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDExample of Truss Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Truss Shoring
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(Photo Courtesy of S.P.S, Inc.)
Example of Truss Shoring
30
Truss Repair Procedure (cont)
• Shore truss up to restore original truss geometry and to remove stress from truss members.
• Manipulate truss with rods or jacks to restore geometry when broken. (Almost like an art.)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Truss Repair Procedure (cont)
• Shore truss up to restore original truss geometry and to remove stress from truss members.
• Manipulate truss with rods or jacks to restore geometry when broken. (Almost like an art.)
• Carefully measure and replace broken truss elements making sure that they are the same length as when fabricated.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Truss Repair Procedure (cont)
• Tighten all original truss bolts (be careful not to over-tighten and crush wood).
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
31
Truss Repair Procedure (cont)
• Tighten all original truss bolts (be careful not to over-tighten and crush wood).
• Re-install new steel tension rods from heel-to-heel one on each side of truss. These rods usually engage the existing heel bolts.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Truss Repair Procedure (cont)
• Tighten all original truss bolts (be careful not to over-tighten and crush wood).
• Re-install new steel tension rods from heel-to-heel one on each side of truss. These rods usually engage the existing heel bolts.
• Tighten steel tension rods in small increments, equally on both sides of truss until truss lifts up off of the shores or until the specified tension is obtained.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs (cont)
• Never recommend the simple replacement of a fractured lower chord element without installing steel tension grods from end-to-end.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
32
Do’s & Don’ts of Truss Repairs (cont)
• Never recommend the simple replacement of a fractured lower chord element without installing steel tension rods from end-to-gend.
• Use kiln dried lumber for replacements or use laminated veneer lumber. I prefer LVL.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs (cont)
• Design and size lower chord tension rods for 100% of dead load plus 100% of live loads. A simple stiffness calculation
i h i i h Ti b Lcomparing the strain in the Timber Lower Chords vs. the strain in the New Steel Tension Rods will reveal that most of live load will be resisted by the steel tension rods. Most of the time the tension rods are tightened for dead load only.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs (cont)
• Always restore the member capacities of the original trusses and their connections so that unbalanced loads have a complete load ppath. Sometimes it is difficult due to physical dimension constraints at original splice locations.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
33
Do’s & Don’ts of Truss Repairs(cont)
• If high strength steel cables are used to reinforce the lower chords of the trusses, it is our standard that the steel cable and its anchoring connections should be sized for g100% of the dead load and 100% of the live load and that the cables be tensioned for DEAD LOAD ONLY. The truss members that were fractured should be repaired to restore 100% of their original capacity for they will resist 100% of the live load.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs (cont)
• If steel tension rods are specified to reinforce a truss with an inside shoeconfiguration remember to design the g gnew heel bolts for bending also. This means that these heel bolts will probably end up being ASTM A490 bolts or SAE Grade 8 high strength bolts.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs (cont)
• If steel tension rods are specified to reinforce a truss with an inside shoe configuration remember to design the new heel bolts for bending also. Thi h h h l b l ill b bl dThis means that these heel bolts will probably end up being ASTM A490 bolts or SAE Grade 8 high strength bolts.
• Rod tensioning must be completed in the presence of a licensed deputy building inspector.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
34
Do’s & Don’ts of Truss Repairs(cont)
• Recommend experienced truss reinforcement contractors only. We require 10 years experience.y p
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Do’s & Don’ts of Truss Repairs(cont)
• Structural observations always required.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
35
Example of
Lower ChordLower ChordTension Rod Reinforcement
Calculation
36
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Example of Truss Repair Elevation
37
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Typical Heel Extension Plate
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
38
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
TYPICAL TRUSS REPAIRS AND/OR
REINFORCEMENTS
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
39
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Truss Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Truss Repair
New Lower Tension Rod © 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
40
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDNew Lower Chord with New Splice and Cable
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDNew Lower Chord with New Splice
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDNew Upper Chord Rib
41
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
New Lower Chord Heel Strap and Rod Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Completed Truss Repair
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDNew Heel Connection
42
Lower Chord Tension Reinforcement with Cable© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Mack-Truss Reinforcement
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVEDMack-Truss Reinforcement
43
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Heel Connection and Seismic Splice for Mack Truss
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Tension Rod at Lower Chord with Web Reinforcement
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Upper Chord Reinforcement by Field Laminating
44
COMMON TENSION ROD
CONNECTIONDETAILS
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
45
Do’s & Don’ts of Truss Repairs(cont)
• Tensioning of steel rods shall be done with a calibrated torque wrench and in the presence of a licensed deputy building inspector.
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
46
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Coupling Nut on Lower Chord Tension Rods with
Witness Holes
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
NEW BOWSTRING TRUSS
CONSTRUCTION
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
47
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
New Bowstring Truss Assembled On-Site
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
(Photo Courtesy of Ed Hansen Roof Structures) New Bowstring Truss being Set In-Place
INTERESTING LAMELLA
CONSTRUCTION
48
Lamella Roof Under Construction (P.F. Changs; Long Beach, CA.)
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
© 2009 by Mackintosh & Mackintosh, Inc.ALL RIGHTS RESERVED
Lamella Roof Under Construction (Legends; Belmont Shore, CA.)
Lamella Rib Is Similar to Bowstring Rib with Compound Mitered Ends© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED
49
Questions?
Contact InformationSteven G. Provenghi, PE,SE,SECB
Mackintosh & Mackintosh, Inc.Consulting Structural Engineers since 1941Consulting Structural Engineers since 1941
3838 Oakwood AvenueLos Angeles, California 90004
1-323-662-1184
[email protected]© 2009 by Mackintosh & Mackintosh, Inc.
ALL RIGHTS RESERVED