wood Flashcards
whats type of wood has interwined growth , bamboo etc
endogenus
what type of wood has outward groth
exogenus
what is another name for hardwood
deciduous
softwood?
evergreen
examples of hard wood/deciduous
ash oak maple
examples of softwood/evergreen
douglas fir, spruce, pine
radiata pine facts
90 % of sawn timber
usa nartive
low durability
douglas fr facts
usa native, pinkish brown, more durabke
whats sapwood
near outside, (1/3) of radisu, takes moisture from roots, stores food.
whats heart wood
inner core, non living cells, more resistanct to decay
pith?
for the new shoot, growing tip of tree
outer bark puprose
protect
inner bark purpose
transport sap to growing plants of tree
cambium
layer inbetween new wood and new bark, repeated subdivisio of cambium formns new wood and bark.
spring wood (early wood)
rapid growth, large diameters
summer wood (late wood)
slow growth , smaller D thick cell walls
what are tracheids
longitudinally allinged cells, mechanical support, transport sap
s3 and s1 layers perpendicular to grain, but thin
s2 layer parallel to grain, thick
cellulose
50% by weight, formed from glucoes
lignin
33% soft wood 35% hard wood phenylpropen units. responsible for longitudinal shear stress
hemicellulose
20% softwood 30 hard wood.
extractives
tannins, oils, resin, colour odour taste decay resistamce, flamibility
chemical compostiiong
c 50 O 44 H 6
equation for strength after extended loading
%=91.5-7log(hours)
moisture content of green wood
30-200%
how is bound water bound
hydrogen bonding to cellulose
where does the most shrinkage occur. and how much for the rest
most in tangential direction, about 2/3 in radial of transverse, very little longitudinal shrinkage
lumber process
harvesting (400-800 mm diameter)
sawing (live sawing (most economic) quarter (most prime cuts), combination)
season-drying, kiln or air
(different shrinkage in different directions creates bow twist crook cup
surfacing (2.5 mm from each side)
types of boards?
flat sawn (grain 45 from flat side) worst rift sawn (45-80) quarter sawn (vertical)
7 types of bad things that can be in wood
knots, slopping grain, core wood, reaction wood, checks, shake, wane.
whats slopping grain
- due to grain distrubuted locallly from branch
- log had fibres growing in a spiral direction
core wood?
less dense, 5-10 grwoth rings from center
reaction wood?
lower side of leaning trunk, has 30 5 more density, leads to warp
checks
differential drying consequence, cracks basically
shake
seperation between annual growht rings
wane
lack of wood at corner
types of grading
presorted (representivitve testing)
strength vclass
visual grading knote etc no more than 1/3 knot area
types of machine grading used
constant load plank (deflection measured) constant deflection (load measured) joist grading (stiffness and strength at joist. defelection measured acoustic grader
what do fungus need
moisture (below 20 % prohibits)
wood.
air (can bury wood)
temp
chemical you can use for fungacide?
chromated copper arsenate CCA
copper and arsenate fungaside
chromium=uv resistive
another chemical ?
ACQ alkiline copper quartenary
whats borates
odourless etc, non toxic, penetrates deep as it is water bourne, cant be applied to wood in contact with wATER
how can you stop fire in wood
pressure impregnation with water soluabkle salts, fiure retardant chemicals sprayed on outside.
what is CLT
cross laminated timber, has dimensional stability
what is LVL
laminated veneer lumber
how to make ply wood
heat and pressure, phenol somthing,
how to make fibrboards
heat and pressure, polyurethane adhesive
composite benifits
resource utilisation insect and fire damaged timber juvenile woood recylced plastic dimensional stability greater durability less variability
composite drawbacks
emissions, mechanical properties, moisture /temp affects, manufacturing energy, resource competition.
what are SLT bridges
stress laminated timber bridges, use of friction, shear transfer and load distributions, retensioning possible
post tensioned timber frames advantages
reconstrucabkle fast and effecient cost effective high seismic resistance sustainable multistory
