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