aaa introduction to timber design-revised2015

8/19/2019 AAA Introduction to Timber Design-Revised2015

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CE 443 - Timber

Design

(Wood Design)(Wood Design)


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Wood is the most widely usedconstruction material in use world-wide.It is used not only or residential rame

construction but also as ormwor!"sca#olding and tem$orary su$$ortraming or commercial and large scale

construction as well.


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%d&antages o Wood

%&ailability ' Wood is a&ailable almost e&ery$lace in the world

ocal labor ' emi-s!illed labor is all that isusually necessary

Easy to wor! with ' ight weight and easy to cutand asten

%esthetics ' *othing com$ares to word or theaesthetic +warmth,with insulation

elati&ely ine$ensi&e ' Dimension lumber isrelati&ely chea$ com$ared to other constructionmaterials" $articularly or small members 'howe&er" hea&y timber members tend tosomewhat $ricey

/ea&y Timber is relati&ely 0re-resistant (charred

eterior o timber insulates interior o timber)


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Disad&antages o Wood

Can decay" needs care with use" treatingor coating

Is 1ammable 'needs co&ering or treating

in many uses 2uality and a&ailability ha&e decreased

oor insulation characteristics ' need to

coordinate with insulation


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ac!ground

i!e all li&ing things trees ha&e a lie cycle5irth

6rowth

%gingDeath

%s trees grow" their $hysical orm changesas does their role in the orest ecosystem


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I7EC8CE 97 TEE

Seedling

Seed

Sapling

Mature Oak

Snag


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eeds

eeds come in a &ariety o sha$es"weights" colors" and si:es" de$ending on the

s$ecies. eeds de&elo$ rom male and emale $arts o

the trees $roducing ruits. ome seeds are in a $rotecti&e nut li!e an acorn

9thers are in 1eshy ruits" li!e the blac! cherry.

The ruit o a $ine is a cone and the seed is wingedand resembles a miniature helico$ter when alling. Wind" water" animals" and $eo$le dis$erse

seeds to the orest 1oor" o$en 0elds" yards androadsides.

Where conditions are a&orable or germination"seeds will germinate and grow.

Which came 0rst -the tree" or the

seed;


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eedling

The seedling grows and begins tode&elo$ woody characteristics.

The stems harden" change color" andde&elo$ a thin $rotecti&e bar!.

The stem may bend or de&elo$

branches that reach toward light. ea&es or needles that de&elo$ are

ada$ted to shade" but lean or tilttoward light.


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a$ling

When the tree is about =-4 inchesin diameter at 4.> eet" it isconsidered a sa$ling. standard height where tree?s

diameter is measured ' diameter at

breast height (D/). %s the tree starts to get taller the

trun! thic!ens and branchesde&elo$.

% sa$ling is the si:e o a treegrowing in a nursery.

In this @u&enile state" the tree is notmature enough to re$roduce.

6rowing ra$idly" the sa$ling hasthe same com$etition and threatsas seedlings.


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What $lant in the$icture would yousay is a mature

tree;


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Decline

The lie s$an o a tree is a wide-range"yet death is ine&itable.

% combination o actors o&ercome atree and causes it to die. In@ury" drought stress" ollowed by

disease" rot" root diebac!" cou$led with a

lightning stri!e or insect inestationcontribute to tree decline.

ometimes a single actor is seriousenough to cause mortality.


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Dead Tree

tanding dead trees" called snags"$lay &ital roles in the lie cycle omany organisms.

% snag slowly brea!s down andreturns nutrients as limbs" bar!" andbranches all. It $ro&ides habitat andood or wildlie and insects.

%nimals" insects" and ungi hel$ brea!

down the tree. E&entually" the snag will all and return

nutrients to the soil where they areta!en u$ by other trees.

%nd" the cycle begins anew.


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What stage o theliecycle are thesetrees in currently;

EEDI*6


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*%6


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%I*6


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Why would we want tomeasure trees;

lan har&esting


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D/

Tree diameter is an im$ortant orestry measure and isused to indicate how well a tree is growing o&er time.

It is also one o the standard measures o timber &olumeused to estimate the commercial &alue o a orest stand.

y con&ention" the diameter is measured at a height on

the trun! that is =.3> m (4.> t) abo&e ground le&el. This height abo&e the ground is used because une&en

swelling and irregular growth at the base o the tree andu$$er roots could mas! the true growth o the trun!.

What would ha$$eni $eo$le measuredtree circumerence

at di#erent heights;


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Tree?s Crown $read

This is a hori:ontalmeasurement5 lea ti$ to lea ti$ o the shortest

s$read lea ti$ to lea ti$ o the longest

s$read through the main mass o the

tree cano$y

%dd the two numbers together"and di&ide by two or thea&erage crown s$read

Crown s$read is diBcult tomeasure when branches arehigh. /a&e $eo$le standwhere the ti$s o the arthestbranches are directly o&erhead.

% 3rd

$erson can measure thedistance at ground le&el.

3 .>eet

= .>eet

What is thecrown s$read o

this tree;

.> eet


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What is the

crown s$read othis tree;

== eet

eet

.> eet


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ea ha$e

Di#er in many ways and hel$ identiy trees Ti$s may be $ointed" rounded" ta$eredF ases may be sGuared" rounded" heart-sha$edF


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What are thesha$es o these

3 lea&es;

%


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ar!

Identiy with the color and teture

haggy" smooth " rough or dee$ urrows

Eam$le5 a$er irch ' white" $a$er-li!e

se bar! on trun!" not branches

a$er irch


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*eedles or road ea&es

In the sim$lest sense we ha&e ty$es o trees5

Coniers (conierous) 5 otwoods

seeds de&elo$ in cones" ha&e needle sha$edlea&es

don?t lose lea&es each year so stay green Ke&ergreens

ines" s$ruces" hemloc!s and 0rs road-lea (deciduous) 5 /ardwoods

broad" 1at lea&es that they lose each year

9a!s" ma$les" beeches and as$ens


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Tree $ecies


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Tree $ecies


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Tree $ecies


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Tree $ecies


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Tree $ecies


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Cross Section of a Tree Trunk


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/istor o Wood


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/istory o Woodtructures

/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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/istory o Wood


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MODERN TIMBER STRUCTURES


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Wood Deects


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Wood Deects


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Wood Deects

d


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Wood Deects

aaa introduction to timber design-revised2015

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