Download - Laminated Timber Columns
Laminated Timber Columns Structural Characteristics by cox06a
An AIA Continuing Education Course
Credit for this course is 1 AIA HSW CE Hour
Cox Industries, Inc.
860 Cannon Bridge Road
Orangeburg SC 29115
www.coxwood.com
© Ron Blank & Associates, Inc. 2012
Please note: you will need to complete the conclusion quiz
online at GreenCE.com to receive credit
AN AMERICAN INSTITUTE OF ARCHITECTS (AIA)
CONTINUING EDUCATION PROGRAM
Approved Promotional Statement:
Ron Blank & Associates, Inc. is a registered provider with The American Institute of
Architects Continuing Education System. Credit earned upon completion of this program
will be reported to CES Records for AIA members. Certificates of Completion are
available for all course participants upon completion of the course conclusion quiz with
+80%.
Please view the following slide for more information on Certificates of Completion
through RBA
This program is registered with the AIA/CES for continuing professional education.
As such, it does not include content that may be deemed or construed to be an
approval or endorsement by the AIA or Ron Blank & Associates, Inc. of any
material of construction or any method or manner of handling, using, distributing,
or dealing in any material or product.
AN AMERICAN INSTITUTE OF ARCHITECTS (AIA)
CONTINUING EDUCATION PROGRAM
Course Format: This is a structured, web-based, self study course with a final exam.
Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour
Completion Certificate: A confirmation is sent to you by email and you can print one
upon successful completion of a course or from your RonBlank.com transcript. If you
have any difficulties printing or receiving your Certificate please send requests to
Design professionals, please remember to print or save your certificate of completion
after successfully completing a course conclusion quiz. Email confirmations will be
sent to the email address you have provided in your RonBlank.com account.
Please note: you will need to complete the conclusion quiz
online at GreenCE.com to receive credit
COURSE DESCRIPTION
This one hour online course will allow the design professional to
gain insight into the makeup and characteristics of laminated
timber columns and compare to other alternatives. We will review
the importance of materials selection, production process, and
testing. We will conclude this course with a brief 10 question quiz
for assessment.
LEARNING OBJECTIVES
By the end of this course, the design professional will be able to:
Explain the construction of the laminated timber column
Describe the importance of proper & sustainable fiber
sourcing, pressure treating to ground contact, kiln drying and
a structural adhesive
Identify the structural advantages of built-up timber columns
Identify the job site advantages of laminated columns
INTRODUCTION
Fiberglass and aluminum columns are structural and can carry
fairly substantial loads, but can often be cost prohibitive. Solid
timbers are cost effective, but can warp and twist and for
aesthetics may need to be wrapped with a veneer. This increased
labor and material can drive up the cost and time required to
install.
THE LAMINATED COLUMN
There is a welcome alternative to columns made from solid
timbers and without the expense of fiberglass and aluminum
products: laminated timber columns made from high grade
pressure treated lumber.
THE LAMINATED COLUMN
Laminated Columns are structural and can be used in place of
fiberglass or aluminum columns to create a substantial cost
savings.
Columns are made from southern pine components joined with
waterproof resorcinol adhesive by a proprietary system.
The columns are treated to ground contact retention levels for
use in porch and deck post applications.
THE LAMINATED COLUMN
Traditional timber columns are prone to warping and cracking
in a short period of time after installation.
Laminated columns have the handsome appearance of veneer-
encased timbers without requiring the extra construction time.
Higher strength, lighter weight, faster construction time
ELIMINATE WARPING, TWISTING…
In the case of the laminated timber column, the whole is truly greater than the sum of the parts. The combination of proper material selection, a laminating process, treatment and re-drying produces a superior and long lasting product.
Start with a truly sustainable building material
Select top grade lumber: Dense #1 and better
Protect the wood by pressure treating
Kiln dry after treatment
Manufacture with an efficient, built-up configuration using a structural adhesive
SOUTHERN FORESTS
Often called "America's Woodbasket."
214 million acres of the U.S. forestland are in the South.
Produces 15.8% of the world's timber production, and 58% of
the timber production in the United States.
SOUTHERN YELLOW PINE
SYP is a softwood species allowing the pressure treating process to reach the cellular level, locking the protection against rot, decay and termites into the wood. SYP also has superior strength and stiffness. It has been a preferred building material for generations as well as the material of choice for engineered wood product manufacturers such as roof and floor truss manufacturers.
Why Southern Yellow Pine?
Superior strength and stiffness
Quality controlled
High density
Best treatability
Natural beauty
The growth of SYP plantations exceeds harvest by 28%
Dense
NonDense
Density Affects Strength
SELECTION OF DENSE FIBER
The inner portion of a growth ring is
formed early in the growing season,
when growth is comparatively rapid
(hence the wood is less dense) and is
known as "early wood" or "spring
wood" or "late-spring wood." The outer
portion is the "late wood" (and has
sometimes been termed "summer
wood," often being produced in the
summer, though sometimes in the
autumn) and is denser.
As you can see, the growth rings on these pieces of wood are wide. This is
an example of a NON-Dense material. There is a lot of SAP wood and little
Heartwood. Also note the material is cut from near the center of the tree.
In the next slide, you will see the examples of a denser material.
The wood here has much smaller growth rings which makes it a dense
material. Also note the wood has been cut further away from the center
toward the outer edges of the tree.
This is decking; again, an example of wide growth rings and material cut
from near the center of the tree.
This is an example of DENSE 5/4 decking material.
Dense material is more stable and reacts more favorably to the elements
than non-dense material, this is especially true if the treated lumber is
kiln dried after treatment to remove excess moisture.
WHAT IS THE TREATMENT?
Wood treated with Copper Azole technology with a blend of dissolved and dispersed copper, which protects against damage from termites and fungal decay.
Active ingredients – Effective! Recycled copper (protects against termites and fungal decay)
Azoles (protect against copper-tolerant fungi) Organic fungicide
FDA approved
AWPA approval in progress: DCA type C (blend of dissolved/dispersed copper azole)
Such treatments enable lumber, plywood, and timbers to last for decades in exterior applications such as decks, fences, walkways, landscaping, outdoor furniture, posts, and building columns. By increasing the longevity of wood, this preservative makes structures safer; and because fewer natural resources are used, impacts on the environment are reduced.
THE SCIENCE OF DCA-C
Compared to μCA-C (micronized copper azole biocide) treated lumber, wood plastic
composite (WPC) requires approximately 17 times more fossil fuel and 2.4 times
more water, and results in emissions with potential to cause three times more
Green House Gases, 6.5 times more acid rain, 2.6 times more smog, 1.7 times
more ecological toxicity, and 3.3 times more eutrophication (chemical run-off)
impact on the environment, than μCA-C-treated lumber. In addition, 9.3 times more
total energy is required during the life of WPC compared to μCA-C-treated lumber. –
AquAeter, Inc. March 2011.
SEM micrograph and EDXA map of a
radial section cut 5 mm inwards
from the surface of Block
11205.1.16 showing uniform copper
distribution along the tracheids. (Dr.
Morrell)
BENEFITS OF DCA-C
Long-lasting protection against termites and fungal decay
Best of new technology with proven efficacy of dissolved copper
Clean, odorless, and familiar treated color
Economical
Ideal for all outdoor projects
Offers environmental benefits of wood
INSIDE THE TREATING CYLINDER
Step 1: Dry wood is loaded into the cylinder
Step 2: An initial vacuum pulls out air
Step 3: Liquid preservative fills the cylinder
Step 4: Pressure forces the preservative into the wood
Step 5: Remaining liquid is emptied for later use
Step 6: Final vacuum removes excess chemical
INSIDE THE TREATING CYLINDER
ADVANTAGES OF RE-DRYING
Wood dries under controlled conditions at treating plant, not after
installation
Minimal shrinkage after placement
Less warping
Lighter weight, easier to handle
Can be painted immediately
Meets building code requirements
Greater nail-holding power
Environmentally preferred
KILN DRYING AFTER TREATMENT
Step 7
Wood is placed in a dry kiln
Step 8
Moisture is removed
Here, materials are entering the drying kiln after the pressure treating
process. Notice the layers are separated by sticks to allow for consistent
air flow during the drying process. The wood is dried in a controlled
environment by a combination of heat, steam and air flow.
QUALITY CONTROL
Standard “wet” treated lumber dries on the jobsite, so any warping, twisting or
cupping happens during or after installation. The KDAT process allows for poor
performing pieces to be seen at the manufacturer’s location, before it makes it
to the retailer or jobsite. Undesirable pieces are removed on stacker. Treating
companies should be able to cite each of the following:
Independent 3rd party audit program
Treating solution monitored by Chemical Manufacturer
Treated to AWPA standards and/or NERs
GROUND CONTACT RETENTION
Treating lumber to ground contact retention is not only important for buried
posts, but also for when a post is used in/on concrete. This means having a
high enough amount of preservative fixed into the cells of the wood to allow the
post to be used in direct contact with the ground. Wood is hydroscopic,
meaning it wicks moisture. Like a fresh cut Christmas tree, a board or timber
will continue to draw moisture from the environment forever. Wood treated for
“above ground use” is meant for that application and should not be used in the
ground or on surfaces like concrete which also draws and retains moisture.
STRUCTURAL DESIGN
Journal of Architectural Engineering - June 2000.
Figure A is an example of a typical
“mechanically connected” box column.
Research has been established on the
structural advantages of this construction
technique.
What is new to the testing being discussed here
is the use of an adhesive connection, which
could allow for controlled construction in a
manufacturing environment. Manufacturing
would construct the columns with a laminating
process, pressure treat and kiln dry the product
before surfacing.
STRUCTURAL DESIGN
Figure B is an example of the
new design technique.
[Built up Box Columns] tested
results in a significant
advantage in load-carrying
capacity of the built-up sections
over solid sections for columns
having dimensions greater than
127x127 mm (5x5 in.).
STRUCTURAL ADVANTAGES CONSIDERED
1. Efficient use of material, allowing significantly greater loads
to be carried and higher allowable stresses to be used.
2. Improved quality control stemming from the use of smaller
dimensional lumber sections.
3. Improved quality control through the use of an automated
fabrication procedure not suitable for traditional box
columns.
4. Reduced cost-to-column capacity ratio.
STRUCTURAL TESTING
By the University of South Carolina, Kent A. Harries and Michael
F. Petrou, Asst Profs dept of Civ & Envir Engineering
Conducted according to specifications provided in the 1991
National Design Specifications for Wood Construction (NDS).
Reported in "Structural Characteristics of Built-up Timber
Columns," published in the June 2000 issue of the Journal of
Architectural Engineering.
TESTING CONCLUSIONS
Figure “A” Columns were tested for
“axial load” or the ability to stand up
to a crushing force.
Figure “B” Columns were tested for
“flexural load” of the ability to stand
up to a bending force.
Laminated columns can be used in a horizontal application as a beam or
header.
TESTING CONCLUSIONS
Allowable stresses for the sawn timber components of the built-
up columns may be used to determine the capacity of the
member. This provides a significant increase in allowable loads
for sections greater than 1093 109 mm.
The sectional and longitudinal dimensional stability and clarity of
the built-up column appears superior to that of larger solid
timbers.
The hollow provided in the built-up columns may be utilized to
enhance structural connections or to provide ‘‘invisible’’
connections.
TESTING CONCLUSIONS
By comparison, these columns exhibited axial stress
capacities approximately 7 times those of equivalent solid
timber posts.
The hollow-built up sections tested may be considered
‘‘solid columns’’ as prescribed by Clause 3.7 of the NDS
specification.
TESTING CONCLUSIONS
University of South Carolina
“When designing against NDS specifications...170% over-
strength against buckling, 370% over-strength against flexure,
240% over-strength against shear [and] when compared to a
solid timber of comparable dimensions, the increase above the
allowable stress improved to 700%”
LAMINATED COLUMNS
STRENGTH PROPERTIES CONFIRMED
A summary of the results of 11 axial load tests, 18 flexural tests,
and 12 axial squash load tests (conducted on Southern Pine
columns) were reported in "Structural Characteristics of Built-up
Timber Columns," published in the June 2000 issue of the
Journal of Architectural Engineering.
DESIGN LOADS
As a safety factor, the design load
standards are published at lower
numbers than where the test result
actually saw a failure. 4 to 10 times
safety factors are often a normal in
engineered products.
OTHER ADVANTAGES: FASTER INSTALLATION
Attractive appearance
Won't twist and no gaping cracks
Lighter in weight
Ready for installation
Hollow core allows for enhanced
structural capability or concealed
wiring
Lifetime limited warranty against
damage from termites and fungal
decay
Can be painted, stained or coated
without delay
When replacing an existing column, place a temporary support beside the column you are planning to replace. Use a 4x4 or 2x6 and a bottle jack if necessary to make sure the load is properly supported. Once the load is supported remove the old column.
CARE & HANDLING TIPS
Keep columns DRY until installation.
Seal with a quality primer and paint upon installation.
Surface “CHECKS” can be filled with wood putty before sealing.
For large quantities being delivered to jobsites other
precautions should be taken. Please notify your distributor or
the manufacturer for more information.
LAMINATED TIMBER COLUMNS
Attractive appearance
No twisting and no gaping cracks
Lighter in weight
Ready for installation
Hollow core creates enhanced structural capability
Ability to conceal wiring in hollow core
Limited lifetime warranty against damage from termites and fungal decay
Treated for ground contact
Paint, stain or coat without delay
Significantly greater load-carrying capacity than solid timbers for dimensions over 5x5
COURSE SUMMARY
Now, the design professional will be able to:
Explain the construction of the laminated timber column
Describe the importance of proper & sustainable fiber
sourcing, pressure treating to ground contact, kiln drying and
a structural adhesive
Identify the structural advantages of built-up timber columns
Identify the job site advantages of laminated columns
Laminated Timber Columns Structural Characteristics by cox06a
An AIA Continuing Education Course
Credit for this course is 1 AIA HSW CE Hour
Cox Industries, Inc.
860 Cannon Bridge Road
Orangeburg SC 29115
www.coxwood.com
© Ron Blank & Associates, Inc. 2012
Please note: you will need to complete the conclusion quiz
online at GreenCE.com to receive credit
