Post on 16-Feb-2021
UNIVERSIDADE DE SÃO PAULO
ESCOLA DE ENGENHARIA DE SÃO CARLOS
DEPARTAMENTO DE ENGENHARIA DE ESTRUTURAS
LABORATÓRIO DE MADEIRAS E DE ESTRUTURAS DE MADEIRA
Wood in civil Engineering : advantagesand new technologies
Prof. Carlito Calil Junior
CHART - LaMEM
DOCENCIA PESQUISA IBRAMEM ABNT
LaMEM
SET
EESC
USP
LaMEM/COURSES
Engenharia
de Estruturas
Ciência e
Engenharia
de Materiais
PÓS-GRADUAÇÃO
Engenharia
Civil
Arquitetura
GRADUAÇÃO
SENAI DER Prefeituras CESP
EXTENSÃO
Atualização
DOCENCIA
LaMEM/RESEARCH
Classificação Caracterização Compósitos Preservação
MADEIRAS
COMPÓSITOS
Dimensionamento
elementos
estruturais
Ligações
pinos
e conectores
Sistemas
estruturais e
construtivos
ESTRUTURAS
DE MADEIRA
PESQUISA
LaMEM/INDUSTRY
SEM FINS LUCRATIVOS DIVULGAÇÃO
REVISTA/CONGRESSOS
Revista Madeira
EBRAMEM e EREMEM
ORIENTAÇÃO
CURSOS
IBRAMEM
LaMEM/NORMALIZATION
CE 02: 126.10
NBR7190/97
ABNT
USE OF TIMBER IN CIVIL
CONSTRUCTION IN BRAZIL
- Wooden houses
- Roof houses
- Formworks
- Large span roofs
- Poles and cross arms
- Logs (colums, beams and piles)
- Pedestrian bridges and bridges
- Sleepers or ties
- Pallets
WOODEN HOUSES
WOOD FRAME HOUSES
TIMBER ROOFS
FORMWORKS
LARGE SPAN ROOFS
POLES AND CROSS ARMS
LOGS COLUMNS AND PILES
TIMBER BRIDGES
RAILWAY SLEEPERS
PALLETS
- paletes
WOOD CONSUMPTION(millions m3)
BRAZIL X USA - ITTO
0
50
100
150
200
250
300
350
400
450
serrada roliça compensado
Brasil
USA
WOOD CONSUMPTION IN USA
- Wooden houses:
- 1/3 of sawn wood = 40 millions of m3
- Glulam
- 1 million of m3
- I beams for wooden houses
- 370.800 linear meters
- Poles for electrification – 90% wood
- Sleepers or ties – 94% wood
PRECONCEPTION IN TIMBER USE
IN BRAZIL
- Cultural (mansonary and the three pigs story)
- Desinformation of wood use: education on courses of
engineering and arquitecture
- Durability of wood (fungi and termites)
- Safety of timber structures in fire situation
Education of Wood Engineering
- Forest Engineer
- Wood properties and timber structures
- Agricultural Engineer
- Rural construction
- Civil Engineer
- Wood properties and timber structures
- Architect
- Constructive system using wood
- Industrial wood engineer- Wood properties
- Timber structures
- Wood Industrialization of timber structures
INSTITUTION FOR WOOD
EDUCATION AND DIVULGATION
- Universities
- Industries
- Institutes
- Associations
IBRAMEM – conferences EBRAMEM
IBRAMEM – actualization courses
-Department of Roads – timber bridges
- Eletrification Deparment – mechanical and physical
wood properties
- SENAI teachers – constructive and structural details
for timber construction
- Wood industries – visual and mechanical timber
structural grading
MANUAL OF TIMBER DESIGN
NORMALIZATION
NORMALIZATION
- CE-02:126.10 – Timber structures
- CE-02:124.25 - Formworks
- CB-31.000.002 - Sawn wood: grading
OUR INDUSTRY
6 ( CO2 + 2 H2O CH2O + H2O + O2 )
ADVANTAGES TO USE WOOD
Wood . There is No Substitute
Energy Efficient Environmentally
Compatible
Renewable and
Recyclable
It takes nine times more energy to
produce a steel stud as it does to
produce a comparable wood stud.
A steel frame building uses 4,000
times more coal, oil and natural gas to
process than wood.
Wood is the only readily renewable
natural resource and it is increasing in
reserves every year.
It takes five times more energy to
produce aluminum siding rather than
wood siding
Aluminum production results in 8
times the air emissions and 300 times
the water emissions of lumber
production.
The total volume of wood growing in
the U.S. is 25% greater today than it
was in 1952.
It takes three times more energy to
extract and produce a concrete block
than to produce its equivalent weight
of wood.
The production of concrete emits 2 to
3 times more carbon dioxide, carbon
monoxide and hydrocarbons than the
production of lumber
Even steel containing 60% recycled
material consists of 40% virgin
material that was mined from the earth
and cannot be replaced.
Producing a 4" concrete slab floor
requires 21 times more energy than
producing a wood deck.
Totally biodegradable wood waste
accounts for only 7% of the volume of
U.S. landfills. Totally NON-
biodegradable plastics account for 25
to 30% of landfill space.
The synthetic materials industries
(plastic, vinyl, etc.) rely on oil and
natural gas for 98% of their raw
materials, and the World Resources
Institute estimates reserves of natural
gas will last only 58 years at 1988
production rates.
Choose Wisely - Choose Wood
MATE-
RIAL
Energy for
production
(MJ/m3)
Strength
(Kgf/cm2)
Elasticity
modulus
(Kgf/cm2)
Energy
/
strength
Density
/
strength
Elasticity
modulus
/
strength
concrete2400
920
(oil) 200 200000 4,6 12 1000
steel7800
234000
(coal) 2400 2100000 97,5 3,3 875
sofwood
600
600
(solar) 300 100000 2 2 333
hardwoo
d 900
630
(solar) 600 250000 1 1,5 417
ADVANTAGES TO USE WOOD COMPARED WITH CONCRETE AND STEEL
density
(Kgf/m3)
Session Outline:
Physiology of timber fibres, cells, grain, growth rings
Moisture content emc and shrinkage
Creep and duration of load effects
Natural growth characteristics
Structural properties of timber
Characteristics of timber -
Relationship to properties
Maximise performance of material
Knowledge of Properties and Performance
Intuitive understanding of timber behaviour
Performance of Timber
Desired performance
• Appearance
• Structural
• DurabilityProperties
Microstructure
Specification
• Material / species
• Grade
• Size
• Protective treatment
Performance of TimberAppearance/Structural/Durability
AppearanceGrain and colour
Feature
Dimensional stability & emc%
StructuralEssential e.g. strength and stiffness
Utility e.g. dimensional stability
- shrinkage/emc
Straightness - bow, spring, cup and twist
DurabilityBiological hazards
Natural resistance / treatment
Microstructure of Timber
Cells - fibres - mainly longitudinal orientation
Bound together with rays
Higher strength and stiffness parallel to grain
rays
rays
cells
fibres
vessels
hardwood
earlywood
rays
latewood
softwood
Grain
direction
Cells
Chemical components of wood - products of photosynthesis
Cellulose - network of molecules
cell walls - microfibrils - fibrous
Lignin - ‘gel’ - acts as bonding agent which ‘glues’ cells
together
Hemicellulose - cross linking - binds cellulose into the cell
Straight
fibresSpirally
wound fibres
Direction of Strength and Stiffness
Direction of grain
Strong parallel to grain & Stiff parallel to grain
Weak perpendicular to grain
Sapwood and Tree Growth
Sapwood -
transfers water and nutrients from roots to leaves
less dense, lighter colour, cell wall thickness increasing
susceptible to attack - treatment required
(Allowed in some species of commercial timber)
Cambium -
growth layer - new wood laid
down on outside of tree
Heartwood
Heartwood -
cells no longer growing
extractives (growth by-products) can
provide protection from attack
Core - (juvenille wood)
oldest wood
at centre - contains pith
laid down when tree young
can be damaged by tree
pre-stress during growth
Moisture in Wood Cells
Unseasoned
timber
removed
bound
water
Growing
tree
free water
Seasoned
timber 15%
25%
fibre saturation
bound waterPartially
seasoned
timber
100%
Moisture in Timber
Moisture content (mc) = weight water
weight wood
in growing tree - mc = 50% to > 100%
felled tree - mc begins to decrease
Fibre saturation point (fsp) (~25%)
above fsp - moisture in cell cavities lost -> little change
in dimension
below fsp - moisture in cell wall lost -> shrinkage perp
to grain
Seasoning - process of removing moisture from
timber
– Kiln drying (steam, LPG gas, solar)
– Air drying
– Other - chemical, microwave.
Equilibrium Moisture content (emc)
Wet atmosphere / Dry wood → moisture moves to wood
Dry Atmosphere / Wet wood → moisture moves from wood
Wood at emc → no moisture movement to / from woodMoisture in wood at
equilibrium with
moisture in atmosphere
Typical emc Indoor air conditioned emc 8% - 10%
Indoor heated emc 8% - 12%
External - coastal emc 14% - 18%
External - inland emc 10% - 15%
Specification of Moisture Content
Seasoned timber:
mc < 15% - close to emc indoors
will shrink & swell slightly as humidity changes
Everything else:
sold as Unseasoned timber
shrinks on further drying
Effect of mc on properties: reducing mc causes
an increase in
strength
stiffness (reduced creep)
durability (reduced risk of attack)
effectiveness of coatings
Usually specified as Seasoned or Unseasoned
A decrease in
dimensions b & d
(shrinkage mainly
perp. to grain)
Longitudinal
shrinkage
Shrinkage
Loss of moisture in range mc
Duration of Load - Creep Deformation
Stiffness: Creep (extra deformation under load)
recoverable - deformation slowly comes out after load removed
irrecoverable - deformation remains after load removed
function of moisture movement, magnitude & duration of load
occurs at all loads
modelled with j2 factor for deflections of beams
Straightfibres
Spirally wound fibres
Creep important for architects
& engineers in choosing deflection
limits
Duration of Load - Loss of Strength
Strength:
increase in duration & magnitude of load causes decrease in strength
irreversible and cumulative loss of strength
modelled with k1 factor
function of duration of peak
load over lifetime of structure
Different load combinations
have different duration of
load effects
(All composite materials
show this effect)
0
0.5
1
1.5
1
5 sec 5 min 5 hrs 5 day 5 mth 50 yr
Instantaneous loadsWind loads
Duration of load
k1
Application dictates selection of
‘clear’ vs ‘feature’
Natural growth characteristics
Natural Growth Characteristics
Appearance enhanced - timber shows its character
Strength decreased: dependent on size and location of characteristic
Knots - part of a branch extending from pith
Checks - small surface cracks, often causedin drying
Included bark - pockets with no wood fibres
Others - pith, resin pockets, shakes...
few characteristics
conspicuous characteristics
Clear
Feature
Natural features in Sawn Timber
Slope of grain
esp. at edges - low strength
perp. to grain decreases strength at angle to grain
Knotscontain weak juvenile wood,
cause slope of grain @ edge
Knots
•discontinuity of grain at edge
•cause slope of grain at an edge
•often reduce strength and stiffness
Gum and resin veins
•less connection across grain
•lower shear strength and stiffness
Checks
•less connection across grain
•reduced shear strength and stiffness
Pith and core wood
•contain weak juvenile wood
Natural features and Properties
Producers minimise problems by•good cutting practice•quality control -grading
Processing Sawn Timber
Trees are prestressed
Cutting boards from trunks
causes stress relief & slow
change in shape of boards
Bent trees can cause slope of
grain in products
Spring is a problem for all
timber
cup
bow
twist
spring
Evaluation of Structural Properties
Small clear specimens -data only reflects wood fibre strength
For timber beams, we must reduce
small clear strengths significantly to
allow for strength reducing natural
features
In-grade testing - commercial sized timber under realistic loading conditions
Commercial timbertensile strength < compression strength
tensile failures - splintery, brittle, sudden, loudcompression failures - wrinkles, ductile, slow, quiet
STRENGHT AND STIFENNESS PROPERTIES:
pinus oocarpafc0 (MPa) fv0 (MPa) Ec0 (MPa) Et0 (MPa) Em (MPa)
41,1 7,8 8278 6094 6786
31,7 7,4 3808 8335 5693
46,4 8,2 12768 13225 9597
43,5 7,7 9502 11906 8604
32,2 8,5 8920 8263 9597
29,7 6,4 3965 8630 8861
46,4 8,2 9813 7390 7000
41,3 5,9 7569 9803 8324
49,5 7,5 9937 11078 8429
27,4 8 7071 6201 5816
58,4 9,1 17150 18587 13206
24,1 8 13524 8826 12232
21,2 8,5 12495 19354 14152
61 7,4 13621 16308 12427
48,3 7,7 9343 11194 8810
59,2 11 15510 11924 7398
53,9 7,9 10516 15179 9262
56 9,6 13761 15394 11002
48,4 7,4 9940 8801 9597
40,9 10,9 7005 11140 6415
36,7 7,7 7368 9062 9597
27,1 8 2727 6889 6354
47,6 8,3 12487 4832 8630
35,7 8,9 5363 8554 5784
47 8,6 11074 6070 8950
37,1 7,7 7580 13801 8166
35,1 9,2 3453 8956 4778
44,9 8,2 10111 11288 8450
50,1 6,8 9217 10537 6194
39,1 7,4 10158 14188 7709
43,8 8,3 7925 8579 8369
43,2 8,1 8388 13234 8169
( ). ( )R SÁrea F s f s ds
−=
( ) ( )R SF s f s
s s+ s
f P A=
( ), ( )R Sf s f s
0
( ) limSs
f s P s S s s →
= +
s
( )Sf s
( )Rf s
)S(f),R(f SR
( )RF s
S R
s
s
DESIGN: STATE LIMIT Sd < Rd
Grading and Durability
Manufactured Wood ProductsLVL
Glulam
Plywood
Others
Grading as a predictor of performance
Grading MethodsVisual / Machine stress grading
Standards
Quality control
Properties related to grading
DurabilityBasic principles of timber degradation
Natural durability
Timber Behaviour
Unique behaviour (strength parallel to grain)
Unique appearance (life, character, warmth)
Unique structure (parallel cells, growth)
Manufactured wood products
• made from wood to maximise
the effect of high strength
parallel to grain
• can still be used for
appearance applications
• quality control in manufacture
can give very reliable properties
Larger members
can be manufactured
from many smaller
cross-section pieces
Limits on size of trees felled
Limits on size of sawn timber
NEW TECHNOLOGIES:
Manufactured products
Used for :large spans -deep beams
large cross-sections -large span truss elements
panel members - bracing, architectural
large panel elements - floor, roof, ceiling cladding (minor axis bending)
Includes:LVLGlulamPlywoodCLTOthers
LVL
Laminated Veneer Lumber
made from laminating thin sheets of wood
most laminates in longitudinal direction
very deep and long sections possible
high strength
Laminates prior to
gluing and pressingFinal LVL sheet
grain in all laminates
LVL GIRDERS
Glulam
Glued laminated timber
made from gluing many small pieces together to form deep member
Strength > individual pieces
potential weakness - finger joints
opportunities for creative architectural use
curved, tapered beams
horizontallylaminated beam
vertically laminated beam
Pyramidenkogel Tower: 120 Meters
Plywood
made by gluing and pressing thin laminates together to form a sheet
grain in laminates in alternate directions - strength in two directions
select face material for appearance products
select glues for environment, durability
uses:
panels (decorative or bracing)
sheets - plate bending (flooring, formwork)
webs (I-beams, box beams)
Final plywood sheet
Seven laminates prior to gluing and pressing
face grain direction
grain in face laminate
WOODEN HOUSES
CLT: CROSS LAMINATED TIMBER
CLT System in Mid-Rise
(5-9 Storeys High)
Other Manufactured Wood Products
Timber flanged steel web joists -
lightweight, open webs give access for service
webs by light tubes, solid rounds, corrugated sheets
• I-beam - timber/LVL flanges, plywood webs
lightweight, suitable for udls on medium spans
• Box beams - timber/LVL flanges, two plywood webs
suitable for larger spans, torsionally stiff, can use decorative plywood
Designed to limit influence
of strength reducing characteristics
Properties & Design of Manufactured Wood Products
Plywood and LVL - thin glued laminates
Characteristics in one laminate have minor effect on properties due to small area involved
Low variability in properties, potential for: -
Higher characteristic properties
Higher reliability
Design of Manufactured Wood products
Manufacturers provide:
Design properties
Design methods
Span tables
Special building practice
Grading
Sorting of products into groups with
similar characteristics and
properties
Structural gradeAppearance grade
Specify product by calling up a specific grade
Sorting Criteria
Appearance Grading
Classification of timber used forfurniture
joinery and architectural trim
decorative building products
Grading rules knot size & frequency (location unimportant)
splits, cracks, checks (size and frequency)
colour, grain uniformity
utility - want, wane, cup, bow,spring, twist
Feature grademakes a feature of natural
characteristics eg knots
Criterion for sort is appearance of timber surface
Appearance Grading - standards
Aust. Standards AS2796, 1810 etc
Industry appearance standardsused for furniture stock joinery, cabinet making
Designers can write own appearance specification, or personally select timber
(Note - price reflects stringency of appearance specification)
Structural qualities:appearance grades with fewer or smaller characteristics generally have high structural properties
even low appearance grades generally have reasonable structural capacity -fewer strength reducing characteristics
Lower strength
Lower stiffness
Higher strength
Higher stiffness
Structural Grading
Used for classification of timber with defined structural properties - includes framing for housing
May include appearance
Each grade associated with a suite of structural properties - limit states
strength - characteristic value based on 5th %ile (conservative -involves safety)
stiffness - characteristic value close to average -realistic for most applications
Criterion for sort is estimated
structural properties of timber
Structural Grading Methods
Structural grading is based on correlation
between strength and a grading parameter
Visual stress grading - presence or
absence of natural characteristics
Machine stress grading - stiffness on
flat (minor axis MoE)
Proof grading - ability to take a proof load. Each piece passed through machine, bending applied at about characteristic strength level. Broken pieces fail -unbroken ones pass
Quality control - verification of grade properties
by testing
AS 2858 Swd
AS 2082 Hwd
AS 1748AS 1748
AS 3519AS 3519
AS 4063
High Stress grade = High strength and stiffness
Timber Stress Grades
Structurally graded products need to be assigned
properties for designers to use
limited number of grade descriptions
most versatile for sawn timber is F-grade system
Strength Stiffness
Stress Grade Structural properties
Structural
properties
DeflectionBendingTension
CompressionShear
Stress Grades
Stress grade is assigned to a package of timber
Stress grade gives structural properties
Each piece in a package can be taken to have
those properties
Timber stamped with Stress grade at grading
• F-grades - commonly used with
all grading methods and with plywood
• MGP grades - used only with seasoned pine
(machine graded)
• GL grades - used only for glulam members
• LVL -each manufacturer assigns own grade
& design properties
Structural grading
Visual Stress Grading Rules
Very different to appearance grading-different characteristics are important
different sizes & location of each feature are allowed
Each piece of timber examined by a trained grader for characteristics known to decrease strength, stiffness or utility
knots - size, location, angle and position in relation to others
slope of grain - on each face or edge
splits and checks
(Checks that may be important to appearance grading may not be important here)
Visual Stress Grading
Visual gradingsorts into
Structural Grades
#1#2 #3 #4
#5
For each species,
Tables assign an F-grade
to each of
the structural grades.
An F-grade may be
stamped on each piece.
eg. For Structural # 3 seasoned jarrah,
F14 is stamped onto each piece.
For Structural # 3 seasoned (imported) SPF,
F7 is stamped on each piece.
F5
F11
F14
F17
F22
F8
Commissioning a stress grading machine requires
in-grade testing to establish the relationship between
grading parameter and the other structural properties
Relies on correlation between a measured
structural property and all others
Minor axis E most commonly used
each piece tested in non-destructive bending about minor axis over most of the length
minimum E value determines grade (F-grade, MGP grade) of whole piece
grade stamp often automaticallyapplied by the machine(visual check after gradingcan over-ride machine grade stamp to downgrade piece)
Structural grading
Machine stress grading
Machine stress grading
Produces better separation of grades, less overlap between adjacent grades
MGP grades must be assigned by machine stress grading
Grade stamp on timber indicates grading method(AS 1748 indicates machine stress grading)
Machine StressGrading
Operation
Stress Grade
F8
F11
F14
F22
F17
F5
Scanning
Gives indication of
density
slope of grain
internal perfections
Potential for the development of very sophisticated
grading methods
Electromagnetic radiation passed through
timber
Proof Grading
Grade verification technique
Timber initially sorted
using a documented process
If too many pieces fail,
producer must adjust initial
sorting process
broken pieces
rejected
Grade verifiedPieces sold as
Proof graded timber
AS 3519AS 3519
Significant major axis bending load applied
Quality Control
Feedback process - production (grading) to be modified by some measure of the output
•AS 4063 - Verification of Grade properties•Grading with QC
•output sampled and tested •results give success of the grading process •feed-back to grader
•Machine Stress Grading requires QCchecks grading parameter and other properties
•Third Party Certificationassure potential users that quality control system is working
•Structural Design Codequality control used in capacity factor (f )
Durabilitylong-term performance
• Grading and durability performance
when old
• Grading performance when new
Capacity to perform satisfactorily for a
specified period
Durability
Biological/ Physical
HazardsWeathering
Fire
Chemical
TIMBER
Species
Natural durability
of heartwood
Maintenance ensures
protection remains functional
Treatmentenhances
durability
of sapwood
Fungi
Termites / borers
Marine
Design Detailing
minimises
exposure
to hazards
Biological/Physical Hazards
⚫Weathering - protection from moisture, sun
•sealants (including paint)
•shading (positioning in structure)
⚫Fire - protection
•sprinkler systems (active)
•insulation eg. fire-rated plasterboard (passive)
•oversized members allow loss through charring (passive)
⚫Chemicals - timber performs well relative to steel/concrete
•resistant to degradation for pH>2 and pH
Hazard Levels
Hazard
Class
Exposure Service
Conditions
Biological
Hazard
H1 Inside above
ground
Fully Protected
Well ventilated
Borers Only
H2 Inside above
ground
Protected from
Wetting nil leaching
Borers and
Termites
H3 Outside above
ground
Moderate wetting
and leaching
Decay borers
& termites
H4 Outside in
ground
Severe wetting
& leaching
Severe decay,
borers & termites
H5 Ground contact Extreme wetting,
leaching &/or critical
use
Very severe decay,
borers and termites
H6 Marine waters
Nth & Sth
Prolonged immersion
in sea water
Marine wood
borers and decay
H6SW Marine waters
Sth only
Prolonged immersion
in sea water
Marine wood
borers and decay
H Classes
H1 least
hazardous
H6 most
hazardous
Natural Durability (Heartwood)
Extractives and
growth
characteristics
affect
natural durability
of timber species
Class Durability Species1 Highly
durable
Ironbark
Tallowwood
Cypress
Turpentine
Forest red gum
2 Durable Spotted gum
Blackbutt
Western cedar
River red gum
Stringy bark (yellow & white)
3 Moderately
durable
Brush box
Rose/flooded gum
Sydney blue gum
Silver topped stringybark
4 Non-durable Douglas fir
Hoop pine
Radiata pine
Mountain ash/ Tasmanian oak
unidentified timbers
Long-term
Performance of TimberCan match natural durability with environmental
hazard to estimate long-term performance of
untreated timber heartwoodNatural
Durability
Class
Heartwood Service Life (years)
H1 Fully
Protected
H3 Above
exposed
H5 In
Ground
Class 1 50+ 50+ 25+
Class 2 50+ 30 15 - 25
Class 3 50+ 15 8 - 15
Class 4 50+ 5 - 8 < 5
COMPOSITE WOOD MATERIALS
LVL SCL PSL PLL
Degradation zone of cross section
(carbonization) in fire situation
Damage due fire situation :
steel x timber
SAFETY OF TIMBER
STRUCTURES IN FIRE SITUATION
SAFETY OF TIMBER STRUCTURES
IN FIRE SITUATION
CALIL@SC.USP.BR
Every time you don´t specify timber, you are helping to
destroy our planet