Thesis I Final Report (Casurina Wood)

8/17/2019 Thesis I Final Report (Casurina Wood)

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Thesis I Final Report

Classifying the Properties of Casuarina

Wood in Egypt and Designing a Wooden

girder beam.

Coordinator : Dr. Sherif Safar

Supervisors : Dr. Khaled Nassar

: Dr. Tamer Brekah

TA : Menas

Done by : Noha El Gebaly

Omar Ewida

Khaled EwidaTariq Dino

Karim Abaza


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Table of Figures

Figure (1) Casurina as wind breaker for the highways-------------------------------------------------------------5

Figure (2) Casurina is planted in sandy dry soil---------------------------------------------------------------------- 5Figure (3) Casuarina as trees and fire wood ----------------------------------------------------------------------------5

Figure (4) Microscopic view of Casuarina wood fibers------------------------------------------------------------6

Figure (5) Peri beam girder GT24-------------------------------------------------------------------------------------------7

Figure (6) GT24 used as girder beam in a slab formwork-------------------------------------------------------7

Figure (7) Purchasing Casuarina wood from el Sabteya-----------------------------------------------------------8

Figure (8) Sawing the tree into smaller lengths for better workability ------------------------------------- 9

Figure (9) Removing the Bark------------------------------------------------------------------------------------------------- 9

Figure (10) ‘Robeya’ Samples are glided onto the blade to create a fair face-----------------------------10

Figure (11) Tarbee3 machine---------------------------------------------------------------------------------------------------10

Figure (12) Samples are dried in the oven----------------------------------------------------------------------------------11

Figure (13) Wood left to sun heat for three weeks----------------------------------------------------------------------12

Figure (14) A reading of 63.3% turned to be 19.4% MC after --------------------------------------------------12

Figure (15) New trial, wood placed as grid.---------------------------------------------------------------------------------13

Figure (16) Machining Center cuts notch-----------------------------------------------------------------------------13

Figure (17) Example of sample after notch was made with Machining center----------------------13

Figure (18) The grip drawings of the four tests required from ASTM----------------------------------14

Figure (19) The drawings with the dimensions of the required grips from the ASTM---------15

Figure (20) Lather Machine-------------------------------------------------------------------------------------------------16

Figure (21) The simple cross section of the grips on AutoCAD-------------------------------------------17

Figure (22) Wire ADM Machine------------------------------------------------------------------------------------------17

Figure (23) The main grips holding the new grips----------------------------------------------------------------18

Figure (24) Water is saved between the wood fibers-------------------------------------------------------------19

Figure (25) The samples are weighted after being dried in electric oven ------------------------------20

Figure (26) A simple drawing of impact test---------------------------------------------------------------------------26

Figure (27) Impact Tests and the sample is being hit by the hammer----------------------------------26

Figure (28) Values obtained from the hardness test--------------------------------------------------------------28

Figure (29) Radial and tangential side Hardness for different species of wood ---------------------29


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Figure (30) Radial and tangential side Hardness obtained for Casuarina SG check-------------29

Figure (31) Universal Testing Machine---------------------------------------------------------------------------------30

Figure (32) Cleavage test Load vs Deformation-------------------------------------------------------------------- 31

Figure (33) Failure of sample at Maximum load------------------------------------------------------------------- 31

Figure (34) Material Tests system (compression machine) -------------------------------------------------- 32

Figure (35) Compression curves from MTS (upper) and ASTM (lower) -----------------------------33

Figure (36) Brooming or End bearing failure as a result of high Moisture content--------------- 33

Figure (37) Shapes of failure in compression------------------------------------------------------------------------34

Figure (38) The graphs between flexure stress and strain of the five samples------------------------39

Figure (39) All the shape failure of the wood------------------------------------------------------------------------39

Figure (40) Failure shapes of the five samplesFigure ------------------------------------------------------------40

Figure (41) Peri girders model GT24 L = 4.2 m-------------------------------------------------------------------41

Figure (42) The basic dimension of the girder beam GT24 with L = 4.2m-------------------------- 42


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Abstract:

This Project is testing one of the most growing woods in Egypt “Casuarina ” Wood to

specify its mechanical and physical properties. Egypt depends totally on imported wood from

several areas as Europe and Australia and that’s why it is so expensive to be used as structure

material in construction industry. If the mechanical and physical properties of wood was as good as

the imported types then it will be an economic gain for wood industry in Egypt. The properties

were measured by several tests according to ASTM standards for wood D-143. The results were

compared to the most commercially important types of wood in Egypt like Oak and Pine wood.

The result were pretty impressive Casuarinf lies second in most of the properties after the white

Oak and it was well known that Oak and Casuarina are considered very Hard wood. A simple

design for a girder beam was made and tested under bending force to be compared to other girder

beam widely used as formwork GT 24 in Peri standards. The comparison not only structure wise

but economically. The test was done but with some deviations in connections and dimensions than

Peri standards due to limitation of manufacturing process its self or in workshops. The result

weren’t better than Peri GT 24 beam but this test wasn’t accurate enough to judge Casuairna wood.

There are recommendations for a better girder beam that carries more using Casurina according

to its properties.


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Background:

Casuarina has a very hard, heavy, dark red-brown structure; hence the name ironwood is

derived from its properties. The Casuarina trees are considered relatively new to Egypt, which

were introduced from South East Asia (Australia) at the beginning of the 19th century. "One of the

common names of Casuarina species, ‘she-oak’, widely used in Australia, refers to the attractive

wood pattern of large lines or rays similar to oak but weaker." (AgroForestry) This species of

Casuarina now breeds in over 15 different countries around the world including Egypt, Hawaii,

India, Thailand, Palestine, and much more. It has extensively been grown outside of its natural

habitat (native Australia). Casuarina Glauca is naturally used as wind shelterbelts along highways

and farms, preventing dust and wind from disturbing anything. It is also considered as a great

source of firewood, even when it's green it may be combusted. Information on this type of wood

in Egypt is limited in terms of its mechanical and physical properties for several reasons. In Egypt

there is a lack of forestry regions, therefore wood is considered as an expensive commodity in theconstruction world. Instead concrete, cement, and steel are considered as the main elements of

the structural world in Egypt. So no one really ever bothered in discovering the possible structural

uses with woods grown in Egypt.

Figure (1): Casurina as wind breaker for the highways


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Casuarina glauca trees may be grown in desert areas however irrigation is required. For the

first six months it requires watering and after that it can survive on minimal amounts of water.

They are considered as moderately fast growing trees, by the age of 7 years the trees reach an

average height of 5m with a survival rate of 72 % (AgroForestry). Casuarina glauca in the Middle

East and North Africa over performs other Casuarinas by reaching a height of 20-25 m in only 12-

14 years. It has a maximum diameter of one meter, as it can reach half its diameter in barely three

years; also it has a "rapid colonizing ability on disturbed soils, especially in coastal or salt affected

situations." (AgroForestry) In addition to Casuarina's easy cultivation, it has many positive effects

on the natural environment by fixing the nitrogen in the atmosphere.

Figure (2): Casurina is planted in sandy dry soil

Figure (3): Casuarina as trees and fire wood


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Scope and Objective:

This project has two objectives; the primary objective of the research is to classify the

mechanical and physical properties of Casuarina wood in Egypt by testing for the compressive

strength, tensile strength, hardness, toughness, shear strength, moisture content and finally the

specific gravity of wood. These tests will all be in reference to the methodologies of the ASTM

standards. In addition to attaining our results, we will compare the results taken from our tests to

other types of woods in the construction industry. The secondary objective of the thesis is to

successfully design a truss looking system using Casuarina wood that is based on aPeri

standardized design for the specific model GT 24 Formwork Girder.

Figure (5): Peri beam girder GT24

Figure (6): GT24 used as girder beam in a slab formwork


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Figure (8): sawing the tree into smaller lengths for better workability during the rest of the process

Figure (9): Removing the Bark


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Figure (10): 'Robeya' Samples are glided onto the blade to create a fair face

Figure (11): Tarbee3 machine


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Drying the Samples

Figure (12): samples are dried in the oven

Although we knew that Casaurina splits, cracks and twists under sudden heating when in its

green phase, we tried to dry it in the oven at 100 degrees and it did split, crack and twist asexpected. Later we tried heating the oven to 60 degrees, some of the samples were unaffected

some ha d less splits, cracks and twists but the moisture didn’t drop as needed that we knew when

we tested them for compression perpendicular. Results of compression perpendicular test, we

rejected due to its end rolling failure which is unacceptable by ASTM.

Important note: We later found out that the lab staff close the oven daily, thus subjecting our

samples to daily sudden heating and cooling! That probably increased the magnitude of sample

deformation.


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The following trials were to leave the wood, in the open air under sunlight. Three Weeks

into that process we bought a moisture meter and were able to test the wood. Some samples

dropped to acceptable moisture content less than 20 degrees others remained as high as 63.3

degrees, pictures below show actual readings on site.

Figure (13): Wood left to dry in the open air

Figure (14): A reading of 63.3% MC which is the maximum for the selected type of wood turned to

be 19.4% MC after the sample left to sun heat for three weeks


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Below is a new trail, by placing the wood on top of each other in a grid shape to increase the

surface area subjected to air. Trial still in progress and its results are unknown.

Figure (15): New trial, wood placed as grid.

Shaping the Specimens:

After cutting and sawing the specimens to the required size, some tests like cleavage test require a

certain notch or cut to be made in the specimen. Samples are sent to the Mechanical Workshop

and a Job order is submitted with AutoCAD drawing of the specimen.

Figure (16): Machining Center cuts notch

Figure (17): Example of sample after notch was made with Machining center


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Preparing the grips

There were four main tests that needed special grips which were not available in the Engineering

labs. Hence, these grips had to be manufactured according to the specifications and dimensions of

ASTM. One of the grip drawings (tension parallel) in ASTM wasn’t provided with any dimension,so it was estimated from the sample dimensions. These are the four grips required:

Cleavage test Tension parallel Tension perpendicular Nail withdrawal

Figure (18): the grip drawings of the four tests required from ASTM

The design of the grips was based on these drawings from ASTM:

Cleavage test


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Nail withdrawal Tension parallel

Tension parallel sample

Figure (19): the drawings with the dimensions of the four required grips from the ASTM


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The material chosen for these grips was steel and it was bought from El Sabteya. The

material was purchased as blocks with bigger dimension than the required, taking in consideration

any loses at manufacturing it. These blocks were cut into smaller blocks with the exact dimension

in the drawings by the Lathe Machine as shown in figure (1). The cross section of each grip was

drawn on AutoCAD without dimensions or any dashed lines on it to be saved as a separate file for

each grip on a floppy disk as file of (DXF – R 12) Figure (2). The Wire ADM machine (figure (3))

used these drawings on a floppy disk to shape the blocks into the required cross section. Then,

the grips were installed into the machines used for testing (universal testing machine) by fixing a

small rod to be held tightly with the machine grips figure (4). There was a another option of

making a smaller adaptor or converter to fix the grips directly to the machine but this option wasn’t

applicable due to the tight schedule and the need to new raw materials.

Figure (20): (Lather Machine)


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Cleavage Nail withdrawal Tension Parallel

Tension perpendicularFigure (21) (the simple cross section of the grips on AutoCAD)

Figure (22) (Wire ADM Machine)


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The main grips of universal testing machine the rod fixed into cleavage grips

Figure (23): the main grips holding the new grips


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Experimental work:

1-

Moisture Content:

Typically a fresh cut piece of wood or green

wood has a section appearing as in figure 1 below.

The bound water is the liquid or vapor chemically

bound by hydrogen bonding to the cellulose of the

wood cell walls. As the free water is the water filling

in the voids or cavities in the wood cells. In terms of

drying the wood, the free water is first released and

the bound water liquid then gradually decreases.

The amount of water content affects the physical and

mechanical properties of wood and limits its uses

structurally.

Figure (24): water is saved between the wood fibers

The objective:

to determine the moisture content of a wood base material, in our case "Casuarina Wood"

of wood base material moisture content. This value will be further used in our research by

providing a wide range of use in our remaining tests, such as Hardness and Toughness.

The procedures:

The methodology of this experiment and all other tests strictly follow the database of the

American Standards Testing Methods. In this case we will refer to the “Standard Test Methods

for Direct Moisture Content Measurement of Wood and Wood- Base Materials” designationD

4442 92. There are several testing methods to do in order to calculate moisture content; we will

choose the Method A Oven Drying (Primary). This method is considered to give the most

accurate results in comparison to the others.

The methods of this test starts by first cutting the samples of the wood at the desired

dimensions, which are ten samples at 5 x 5 x 10 cm. The test will require a kiln or oven to dry the


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samples to the oven-dry state. The oven used in this case will be an electric oven which will have a

temperature of 103°C ± 2°C. The samples are then numbered and weighed initially to get the

green weight and then placed in the oven at the right temperature. The samples are kept in the

oven at three hour intervals and their weights are recorded between every interval. Note , make

sure to keep that the lab room relative humidity must be less than 70% and the humidity exposed

to the samples to be consistent to achieve the best results. The endpoint of this test is reached

when the difference between the weight levels is extremely small and is considered to be negligible.

At that point the final weight level achieved is considered to be as the oven-dry weight of the wood.

As soon as the oven-dry weight is reached the data collected will be used in order to

calculate the moisture content of Casuarina Wood. The water content is calculated by simply

finding the difference ration between the initial (green) weight and the oven-dry weight. In addition

after performing the experiment the after (drying) dimensions of the samples are used to calculate

the radial and tangential shrinkage ratios, which are significant in terms of knowing the wood's

behavior with seasonal expansion. Look in the Data and Results section for the representation of

this experiment's results.

Figure (25): the samples are weighted after being dried in electric oven every three hours


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Data and Results:

Specimen

no.

Specimen

Dimensions

(before)

cm

Specimen

Dimensions

(After)

cm

Initial

Weight

gm

W1

gm

W2

gm

W3

(gm)

W4

(gm)

W5

(gm)

W6

(gm)

W7

(gm)

W8

(gm)

1 5 x 5 x 10 4.4x4.3x10.3 277.06 246.43 224.28 191.24 168.5 161.00 152.1 147.66 147.11

2 5 x 5 x 10 4.4x4.4 x

9.8

274.02 245.70 222.41 200.84 165.00 158.50 151.08 147.43 146.87

3 5 x 5 x 10 4.3x4.2x10.2 290.57 258.80 236.60 214.30 180.15 173.00 160.30 158.07 156.15

4 5 x 5 x 10 4.2x4.3x10.2 280.28 250.89 224.98 200.65 162.50 157.00 148.23 144.51 144.08

5 5 x 5 x 10 4.4x4.5x10.3 278.13 250.10 226.60 203.11 167.00 160.00 151.85 147.93 147.45

6 5 x 5 x 10 4.2x4.5x10.3 273.19 242.25 218.26 195.28 158.25 153.00 145.02 141.40 140.81

7 5 x 5 x 10 4.4x4.4x10.3 280.98 248.98 225.65 202.84 167.50 161.50 154.84 150.90 150.45

8 5 x 5 x 10 4.6x4.6x10.4 265.97 238.36 218.41 196.26 166.0 160.00 153.88 149.75 149.22

9 5 x 5 x 10 4.4x4.6x10.1 276.06 247.95 225.20 204.10 173.36 166.50 158.05 153.29 153.29

10 5 x 5 x 10 4.6x4.6x10.1 265.79 233.24 212.72 194.82 167.85 160.00 153.50 148.87 148.87

Average 5x5x10 4.39 x 4.45

x 10.19

276.21 248.06 224.01 200.03 167.45 161.05 152.87 149.07 148.43

Note

: between each weight level (no.) there is a three hour interval

Therefore the oven dry weight is represented in the final column on the final row, which is 148.43

grams.


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Moisture Content Calculations

M.C. = (A-B) / B x 100

Where:

A = O riginal Mass (g)

B = Oven-Dry Mass (g)

m.c. 1 = (248.06-148.43) / 148.43 = 86.1

m.c. 2 = (224.01-148.43) / 148.43 = 50.42

m.c. 3 = (200.03-148.43) / 148.43 = 34.7

m.c. 4 = (167.45-148.43) / 148.43 = 12.8

m.c. 5 = (161.05 – 148.43) / 148.43 = 8.5

m.c. 6 = (152.87 – 148.43) / 148.43 = 4.44

m.c. 7 = (149.02-148.43) / 148.43 = 0.43

Moisture Content = (276.205-148.43) / 148.43 x 1 = 86.08 %

Note: m.c1, m.c.2, and m.c. x, represent the moisture content of the samples at a certain semi-oven

dry state. These values are used in order to plot the moisture content and time curve shown

below.

0

20

40

60

80

100

0 10 20 30

W a t e r C o n t e n

t ( % )

Time (Hours)

W.C. vs Time


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2-

Specific Gravity:

The specific gravity is the property revealed in the wooden profile which gives a relevant

idea of the density of the material. Basically specific gravity is the measurement of actual wood

substance in the wood. This value is significant in terms of calculating other wooden properties

and it also gives us an estimate of the weight of the wood substance in the sample.

The methodology used for this experiment is according to the ASTM D-2395 reference.

The method used isMethod A Volume by Measurement .

In order to calculate the specific

gravity with this module the value of the moisture content achieved previously is extremely

significant to the calculation of the needed value. According to the ASTM D-2395 the equation

used to calculate the specific gravity is represented as follows Specific Gravity = K x W /

((1+(M/100)) L x w x t.

Where :

W = oven-dry weight (grams)

M = Moisture content

L = Length (cm)

W = width (cm)

T = thickness (cm)

K = 1 when weight is in grams and volume is in cm3

Therefore,

Specific Gravity = K x W / ((1+(M/100)) L x w x t

Sp. Gr. (Casuarina) = 1 x 148.43 /((1 +(0.86/100)) 4.39 x 4.45 x 10.19= 0.45 g/cm3

The value achieved for the specific gravity of Casuarinas Wood is 0.45 g/cm3. This value basically

means that if a sample of Casuarina Wood is submerged in a tank of water it would float, since it

density is less than that of water's, which is 1 g /cm3.

However by comparing the values of Casuarina wood with other woods, one is able to create a

bigger picture of the stance Casuarina wood takes in comparison with other types of woods in the

world.


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Specific Gravity table:

Wood - seasoned & dry g/cm3

Afromosia 0.705

Apple 0.66-0.83

Ash, black 0.54

Ash, white 0.67Aspen 0.42

Balsa 0.17

Bamboo 0.30 – 0.40

Birch (British) 0.670

Cedar, red 0.380

Cypress 0.510

Douglas Fir 0.530

Ebony 0.96 – 1.12

Elm ( English ) 0.60

Elm ( Wych ) 0.69Elm ( Rock ) 0.815

Iroko 0.655

Larch 0.59

Lignum Vitae 1.28 – 1.37

Mahogany ( Honduras ) 0.545

Mahogany ( African ) 0.495 – 0.85

Maple 0.755

Oak 0.59 – 0.93

Pine ( Oregon ) 0.53

Pine ( Parana ) 0.56

Pine ( Canadian ) 0.35 – 0.56

Pine ( Red ) 0.37 – 0.66

Redwood ( American ) 0.45

Redwood ( European ) 0.51

Spruce ( Canadian ) 0.45

Spruce ( Sitka ) 0.45

Sycamore 0.59

Teak 0.63 – 0.72

Willow 0.42

Casuarina (Egypt) 0.45

Keep in mind that in the wood construction world, wood is classified into three categories,

softwood, hardwood, and manufacture wood (such as plywood). Some softwoods are pine, fir,

spruce, hemlock, cedar and redwood. And some of the hardwoods are oak, maple, cherry, birch,

walnut, ash and poplar. Note that these are all types of woods located in North America (U.S.A)

which are seasoned and dried in a somewhat different environment (therefore keep in mind that

their might be some deviations to the results compared to ours). Our Casauarina wood


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(Hardwood) is completely oven-dried therefore it's seasoned to a different limit. In general

seasoned wood means that the wood has been air dried containing only 15-20% moisture content.

In terms of using wood in construction there are several variables which imply on the

substance's dependency in the field. These variables include the strength, hardness, grain

characteristics, cost, stability, weight, color, durability and availability. In terms of the value we

achieved 0.45 g/cm

3

is considered to be somewhat as a positive outcome, since we know now thatthe weight of this species is not high, which is significant to other characteristics in wood uses.

Shrinkage R atios:

After performing the moisture content test, we are able to calculate the shrinkage ratios of

Casuarina Wood. There are two ratios, the radial shrinkage ratio and the tangential shrinkage

ratio. By using the oven-dry dimensions and green dimensions from the moisture content

experiment we are able to calculate such figures. Shrinkage is the degree of shrinking a substance

has in terms of its exposure to moisture, since most wooden species deform volumetrically when

dried. In this case our substance Casuarina wood shrinks because of water moisture being released

due to the drying process. The significance of the shrinkage ratios is really important, since one

will be able to determine the seasonal behavior or changes to the wood species during different

seasons of the year (different climates).

After performing the moisture content test, you will realize that

there is a column in the data table which represents the

dimensions of the samples after oven-drying. With these values

and the original dimensions we were able to calculate the

shrinkage ratio.

Radial Shrinkage:

It’s the amount the wood has shrunk across the grain

L oven-dry / L original 6.32 cm / 7.70 cm = 0.89

Note: the dimensions are taken according to the cross section of

our wood as shown in the figure 1s below

.

Tangential Shrinkage:

The amount of wood shrunk along the grain.

L oven-dry / L original

4.2cm / 5 cm = 0.84

The values of the tangential shrinkage and radial shrinkage are unit less, and the significance of

these two values is represented by taking the ratio between them, Tangential / Radial.

T/R ratio = 0.84 / 0.89 = 0.00943

L

L


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The smaller the value of the T/R ratio, the more likely the wood specimen would remain flat and

avoid warping due to seasonal changes. This value shows the stability of the wood species to

changes in the surrounding environment (especially in terms of exposure to humidity).


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3-Toughness test:

The test was done using the Charpy method, using 10*10*55mm samples. In accordance with

testing procedures a 2mm notch was made with 45 degrees done in mechanical lab using

machining center.

Figure (26)

: a simple drawing for Toughness sample

Test Procedure:

First the specimen is placed horizontally on the base of the impact machine, with the notch

centered and facing the other side of the hammer. Basically a hammer is dropped from a specified

point indented on the machine’s scale above hitting the specimen and swinging to the other side.

The difference between the initial height of hammer and highest height it swings to after hitting the

specimen results in the energy absorbed by that specimen. The results with their moisture content

are displayed in the following table.


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Figure (27): Impact Tests and the sample is being hit by the hammer

The Results:

• Wsemi=(1+WCsemi)*Wdry

•

WC= Wwet-Wdr Wdr


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4- Hardness test

Objectives:

to evaluate the hardness values determined from tests on specimens of Casuarina wood .second

objective is to compare the results we obtained for Casuarina with the hardness of other types of wood. This test is important because it measures how much a specimen could hold before plastic

deformation. The test was done according to ASTM D143-09.

Procedure:

Hardness test was conducted using Brinell machine (modified ball test) by using a steel ball with a

10 mm diameter. Then the load was recorded at which the ball has penetrated to half its diameter.

The penetrations were far from the edges in order to prevent slipping or chipping and were

applied both to the tangential and radial surface of the wood specimen. The load was applied was

applied on a continuous basis and then the weight and the moisture content of the specimen tested

was measured.

Results:

The results for 21 different specimens were listed in a table and an average of 917.5kgf was

obtained as shown in fig (29). the average was obtained is compared to hardness of other types of

woods and we found out that it exceeded all the wood types in the fig(30) except true hickory.

Casuarina has exceeded red oak and Douglas fir (both types of wood heavily used in construction

industry). However, it should be noted that hardness is only one of the properties and not the only

property that it was taken into consideration when evaluating types of wood.

Figure (28): values obtained from the hardness test


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Figure (29): Radial and tangential side Hardness for different species of wood

Figure (30): Radial and tangential side Hardness obtained for Casuarina SG check

• H(lbf) = 4090(G12/(1+0.162G12))

G12 specific gravity at 12 moisture content

H = hardness in pounds force

Our value for the SG check was 778

Deviations:

• The rate of the machine was not according to ASTM standards and was supposed to be

6mm/minute. .

• 10 mm steel ball instead of 11.4 mm

• When performing the SG check the sample we used was not 12% but was about 8-9%

water content.

Species No. Of

Samples

Mean

Radial (lb.f)

Min

Radial

(lb.f)

Max

Radial

(lb.f)

Mean

Tangential

(lb.f)

Min

Tangential

(lb.f)

Max

Tangential

(lb.f)

Casuarina 21 2022.7 1433 2755.77 1339.3 881.84 1763.69


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5-Cleavage test:

Objectives:

main objective is to form an initial idea of the cleavage values of Casuarina and to test whether our

newly formed grips were working .This test is important because it measures the resistance ofCasuarinas to splitting. The test was done according to ASTM D143-09 and was performed on the

Universal testing machine shown in Fig (32) that had a load capacity of 50 kN.

Procedure:

The specimen was held during the test in the grips as shown in Figs.(32) and (33).Then load was

applied at a rate of motion of 2.5mm/min and only maximum load was observed which is basically

the load at failure. Samples were cut into small cubes (5*5*9.5) cm then shaped with the

required groove according to the ASTM standards and dimensions provided in figure (32)

below.

Fig (31): Universal Testing Machine


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Figure(32): a cleavage specimen as shown in ASTM

Results:

The maximum load is recorded only like in sample 1 graph maximum load is 4 KN as shown in

Fig(11). The maximum load in this case, is smaller than loads recorded in other tests. This is

mainly because the tension applied is carried only by the glows of specimen. The shape of failure

was also sketched from Fig (33).

Fig (33): Cleavage test Load vs Deformation


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Fig (34): failure of sample at Maximum load


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Results:

Mean Stress: 0.797 Mpa

Mean Modulus of Elasticity: 14.12 Mpa

Cleavage

Sample

No.

Maximum

Load (N)

Extension

at Break

(mm)

Length

(mm)

Moisture

Content

Area

Stress

(Mpa) Strain

Modulus

of

Elasticity

(Mpa)

1 4016.66 2.2 50 58 40 1.004165 0.044 22.82193

2 3505.85 2.5 50 58 40 0.876463 0.05 17.52925

3 2334.72 2.3 50 58 40 0.58368 0.046 12.6887

4 3741.34 2.4 50 58 40 0.935335 0.048 19.48615

5 2661.54 4 50 58 40 0.665385 0.08 8.317313

6 2840.56 4.2 50 58 40 0.71014 0.084 8.454048

7 3395.54 2.8 50 58 40 0.848885 0.056 15.15866

8 581.34 2.5 50 3.7 40 0.145335 0.05 2.9067

9 3019.36 4.4 50 58 40 0.75484 0.088 8.577727

Mean 3189.4463 3.1 50 58 40 0.797362 0.062 14.12922

S.D. 572.13238 0.9335034 0 0 0 0.143033 0.01867 5.551832

Figure (35): Similar failure was observed while testing; the picture below shows we

had a similar fracture.


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37

6-

Compression perpendicular to Grain test

Objectives:

Our main objective was to find the compression perpendicular to grain values determined

from tests on specimens of Casuarina wood. It shows the level of weakness of wood to handlecompression perpendicular to its grain compared to parallel to grain. This test is important

because joints and beams are usually supported or placed over on certain areas. As result the

compressive strength of the wood in perpendicular direction should be sufficiently high. The test

was done according to ASTM D143-09 on the MTS machine.

Figure (37): Comp- perpendicular

in ASTM

figure (38):comp. perpendicular as

one in the test without a plate

Figure (36): Material Tests system

(compression machine)


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Procedure:

The compression perpendicular to grain test was made on a50 by 50 by 150 mm specimen. The

Load was applied through a metal plate placed (5 cm by 5 cm) at right angles to the length

(grain) like in figure () .The load was applied continuously at a rate of 0.305 mm/min and then themoisture content of the samples tested was measured. Loading of the sample should be stopped

once it reaches deformation of 2.5 mm. the graph of this test is between load (KN) and

deformation (mm).

Results and Discussion:

There is no true ultimate strength value as the wood gets more crushed with higher load. It’s

merely becomes consolidated and harder to crush further. As the load increases, additional wood

cell farther from the surface, and collapse and the strength increases again. Some of the samples

we were tested till the capacity of the machine were reached (450 KN). Thus, failure here is not

about reaching the ultimate load, but rather reaching a limit beyond which the degree of distortion

is considered unacceptable. According to ASTM this limit was specified to deformation 2.5 mm

then the load shall be discontinued. Some of the graphs didn’t have a limit where distortion started

to happen but the graph is totally a straight line. This kind of unfamiliar graphs is due to excessive

moisture content or distortion of the shape of the sample itself because of improper ways of drying

it in oven. This is the table of the results with the maximum load presented by the machine before

the distortion of the sample and the second column is the load divided by the area (0.15*0.05). the

table is followed by graphs of the samples.

sample no. max. load (KN) max. pressure (Mpa)1 65 8.67

2 27 3.60

3 24 3.20

4 65 8.67

5 80 10.67

6 50 6.67

7 52 6.93

8 60 8.00

9 60 8.00

10 20 2.6711 15 2.00

mean 47.09 6.28

max 80.00 10.67

min 15.00 2.00

comp. perpendicular

Figure (39): the max pressure results for all the 11 samples of compression perpendicular test


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0

20

40

6080

100

120

0 0.5 1 1.5 2 2.5 3

L o a d ( K N )

deformation (mm)

perp 1

0

5

10

15

20

25

3035

40

0 0.5 1 1.5 2 2.5 3

L o a d ( K N )

deformation (mm)

perp 2

0

10

20

30

40

50

60

0 1 2 3

L o a d ( K N )

Deformation (mm)

Perp 3

0

20

40

60

80

100

120

0 2 4 6 8

L o a d ( K N )

Deformation (mm)

Perp 4


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Figure (40): graphs of all the samples (load KN Vs. Deformation mm)

0

20

40

60

80

100

120

0 1 2 3

L o a d ( K N )

Deformation (mm)

perp 5

0

10

20

30

40

50

60

70

0 1 2 3

L o a d ( K N

)

deformation (mm)

perp 6

-10

0

10

20

30

40

50

60

70

0 1 2 3

L o a d ( K N )

Deformation (mm)

perp 7

0

10

20

30

40

50

60

70

0 1 2 3

L o d ( K N )

Deformation

Perp 8

-10

0

10

20

30

40

50

60

0 1 2 3

L o a d ( K N )

Deformation (mm)

perp 9

0

10

20

30

40

50

60

70

0 1 2 3

L o a d ( K N )

Deformation (mm)

perp 10


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Fig (41): compression curves from the ASTM

Deviation:

1- The test was done without the small metal plate (5 by 5 cm) the compressive force was on

all the sample area.

2- Some of the samples had a graphs with a straight line rather than a curve as presented in

ASTM so the ultimate load was taken at 2.5 mm deformation.

3- The samples were done at different time so the moist ure content weren’t the same for all

the samples.


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Figure (42): some of the samples that were tested for compression perpendicular and last photo

have the sample with the least moisture content.


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7-

Compression parallel to Grain test

The Objective:

Members such as columns and posts and struts must resist loads that are applied

compressive forces which are parallel to its full length. In this test, the ultimate compressive

strength of the Casurina wood longitudinal to its axis. The test was done according to ASTM

D143-09 on the MTS machine.

The procedures:

The sample size is (50 by 50 by 200) mm and loading rate was 0.003 mm/mm. The longitudinal

load is applied increasingly until compressive strength is well beyond the defined elastic limit or

until the specimen fails. The tests shall be continued but not after 150mm. A stress strain curveshould be made from these results and get the ultimate stress for each sample and get the average.

Also the failure type and shape shall be noticed according to the appearance of the fracture surface

even if the failure was a mix of more than one type. All the failure types should be described

because it indicates some of wood properties and

its behavior under the load. Figure () describes all

types of possible wood failure under compression

parallel according to ASTM D-143.

figure (43): a sample data sheet for Figure(44): sample for compression

parallel after failure

parallel Test


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Results and analysis:

compression parallel

Sample. No Max. pressure (Mpa)

1 582 37

3 49

4 20

5 18

6 32

7 44

8 60

9 45.00

10 60.00mean 42.3

max 60

min 18.00

Figure (45): the max pressure results for all the 10 samples of compression parallel test

0

10

20

30

40

50

60

0 0.01 0.02 0.03

S t r e s s ( M P a )

strain (m/m)

parallel 1

0

5

10

15

20

25

30

35

40

0 0.02 0.04 0.06

S t r e s s ( M P a )

strain (m/m)

parallel 2


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Figure (46): graphs of compression parallel samples

0

10

20

30

40

50

60

0 0.01 0.02 0.03

S t r e s s ( M P a

)

Strain (m/m)

parallel 3

0

5

10

15

20

25

0 0.005 0.01 0.015 0.02

S t r e s s ( M p

a )

Strain (m/m)

parallel 4

0

5

10

15

20

0 0.01 0.02 0.03

S t r e s s ( M p a )

strain (m/m)

parallel 5

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02

s t r e s s ( M P a )

Strain m/m

parallel 6

0

10

20

30

40

50

0 0.01 0.02 0.03

s t e s

s ( m p a )

strain (m/m)

parallel 7

0

10

2030

40

50

60

70

0 0.005 0.01 0.015 0.02 0.025

s t r e

s s ( m p a )

strain (m/M)

parallel 8


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Failure shape:

According to ASTM failure types of compression parallel, the most common one in these

tests were “compression and shearing perpendicular” failure which usually happens for

cross grain wood which is the case foe Casurina. The second most common failure is

crushing for the green samples with more moisture content. The end rolling failure is not

acceptable which happened for only one sample due to it improper cutting and excessive

moisture content.

Fig (47): shapes of failure in compression

crushing

Wedge split

shearing

splitting

End Rolling

Compression and

shearing perpendicular

to grain


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Deviations

1- Samples were loaded in rate 1 mm/min instead of 0.302 mm/min as mentioned in ASTMbecause of machine limitations

2- Samples were tested at different stages so some samples have moisture content differentthan others significantly which affected the failure shape.

CrushingSplitting


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8-

Tension Perpendicular to Grain:

Objective: The main objectives of this test are to determine the yield stress, tensile stress,

modulus of elasticity and behaviors of casuarinas wood when subjected to an axial tensile load.

Machine Used: Universal testing machine

Procedure: Fasten the specimen in grips and observe maximum load.

The specifications from ASTM:

1. Size of the Specimen: 5cm*5cm*6.3cm

2. Radius of Grooves: 13mm radius after

penetrating inside of sample a distance of

6mm (Groove to be done on both sides of

specimen) as explained in figure ()

3. Rate of loading: (2.5mm/min)

Figure (49): tension perpendicular sample

according to ASTM standards

Result and analysis:

Only the maximum load is recorded and the average of the 10 samples is taken as the tensile

strength of Casurina wood. Almost all of the samples were green and not dry enough. Many of the

samples were photographed after the failure and almost all of the samples have same shape of

failure as shown in the figure ().

Maximum load: 2773.38 N

Maximum Extension: 1.6mm

Mean Tensile stress: 93.338 Mpa

Mean Modulus of Elasticity: 148847.68

Mpa

Figure (50): Sample No.1 Tension

Perpendicular to Grain


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Table of all the results for nine samples

Tension Perpendicular

Sample

No.

Maximum

Load (N)

Extension at

Break (mm)

Length

(mm)

Moisture

Content

Area

(cm^2) Stress (Mpa) Strain

Modulus

(Mpa) 1 2773.38 1.6 50 58 12.5 2.218704 0.032 69.3345

2 4555.45 2.4 50 58 12.5 3.64436 0.048 75.92417

3 5442.29 3.8 50 58 12.5 4.353832 0.076 57.28726

4 5015.18 2.6 50 58 12.5 4.012144 0.052 77.15662

5 5062.9 4 50 57 12.5 4.05032 0.08 50.629

6 6156.12 3.1 50 58 12.5 4.924896 0.062 79.43381

7 5714.13 2.5 50 58 12.5 4.571304 0.05 91.42608

8 5411.07 4 50 58 12.5 4.328856 0.08 54.1107

9 5221.12 1.2 50 57.4 12.5 4.176896 0.024 174.0373

Mean 5322.2825 2.95 50 57.8 12.5 4.257826 0.059 82.50062

S.D. 482.69654 0.97394632 0 0.38544964 0 0.38615723 0.019479 39.63647

Figure (51): simple sketch from

ASTM D-143 for a sample failure

Figure(52): some of the tension perp. Samples after

failure


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9-

Tension Parallel to grain (ASTM D143):

Objective

:

Some members like the bottom chord of a truss are subjected to tension parallel to its

grain. The slope of grain of each type of wood affects significantly on the tension value so this test

is to measure the value at which the sample fails in tensile force in parallel to the grain.Procedure:

1- Sample should be shaped as shown in the figure () below according to the ASTM standardsand same goes to the grips as described in the grips section earlier in the report.

2- Machine used is Universal Testing Machine

Figure (53): Tension parallel specimen according to ASTM

The Figure (54): a sample after being done according to dimensions Standard in ASTM and then

fixed to one of the grips.


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Results and analysis:

Tension Parallel

Sample

No.

Maximum

Load (N)

Extension

at Break

(mm)

Length

(mm)

Moisture

Content Area

(cm^2)

Stress

(Mpa) Strain

Modulus

(Mpa)

1 5516.66 3.37 460 4.2 0.5 110.3332 0.007326 15060.32

2 4688.38 3.41 460 5.6 0.5 93.7676 0.007413 12649

3 3100.81 2.2 460 6.6 0.5 62.0162 0.004783 12967.02

4 4359.54 3.18 460 7.5 0.5 87.1908 0.006913 12612.51

5 4341.47 4.19 460 4.3 0.5 86.8294 0.009109 9532.583

6 6009.54 2.9 460 7 0.5 120.1908 0.006304 19064.75

7 1147.96 3.25 460 9.3 0.5 22.9592 0.007065 3249.61

Mean 4669.4 3.2083333 460 5.866667 0.5 93.388 0.006975 13647.7

S.D. 1017.6651 0.6546882 0 1.399524 0 20.3533 0.001423 3187.677

Mean Tensile stress: 93.338 Mpa

Mean Modulus of Elasticity: 148847.68 Mpa

Mean Extension at Break: 3.25mm

Maximum Force: 5516.66N

Shape of failure:

The three figures above show the two types of fractures that were seen while testing.

Basically the fracture starts somewhere around the smallest cross section area of

0.5cm^2. Notice how the fracture doesn’t happen exactly at the middle due to wood

being a non-homogenous material.


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Figure (55):

all shapes of failure it was produced by tension force parallel to grain.

Figure (56):

shapes of failure in ASTM

F

F

i

Figure (57): Sample Number one Tension

Parallel to grain:

Deviation:

1- A gage was supposed to be added at the center part of the sample to measure

deformation, but the universal testing machine gave us automatically the extension thathappened due to testing.

2- Deformations were measured/read to 0.01mm.3- The sample weren’t exactly as the shape required with a radius of 444mm however it

was made to the center part with a slope that gave the same look and almost the effect

but the circular shape would be more homogenous in the effect of distributing the

tensile force on the center part.


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10- Static Bending Test

This test is not totally finished. 15 specimens should be tested but only 5 are done but it

gives a simple idea about this test.

Objective:To determines the ductility or the strength of a material by bending the material over a

given radius and provides insight into the modulus of elasticity. Following the bend, the sample is

inspected for cracks on the outer surface.

Machined used: Universal testing machine (100 KN)

The specifications from ASTM:

Size of the specimen: 50 by 50 by 760 mm

The span length: 710 mm

Rate of loading: (2.5 mm)/min

Load deflection curves: Load-deflection curves shall be recorded to or beyond the

maximum load for all static bending tests. The curves shall be continued to a 6 in. (150 mm)

deflection, or until the specimen fails to support a load of 200 lbf (890 N)

The deviations from the ASTM:

There wasn’t any wide machine available in the labs that could tests a sample wide as 760

mm and provide stress strain curve so it the size of specimen was chosen to be the secondary

choice to be applicable for universal testing machine and hence, some of these specification has

been changed according also to ASTM specification and these are the new standards.

Size of the specimen: 25 by25 by 410 mm

The span length: 360 mm

Rate of loading: (1.3 mm)/min

Load deflection curves: The curves shall be continued to a 3 in. (76 mm) deflection or

until the specimen fails to support a load of 50 lbf (220 N) for secondary method specimens.


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Results:

The average stress is: 75.64 which is considered a very high value for wood material.

This test were done on the secondary dimensions and samples were tested half of them at

one time and the other half after two weeks which affected slightly on the moisture contentof the samples. This test is considered the most perfect test was done in this research

because the samples were quit thin (2.5 by 2.5 cm) and it was left for enough time to be

dried so at the end it produced a very high value as bending stress.

Specimen label Maximum Load Maximum Stress Flex Modulus Moisture Content

(KN) (MPa) (MPa) %

1 2.32218 80.25 7409.8 6.3

2 2.8092 97.09 10504.47 7.23 1.79034 61.87 5405.69 6.8

4 2.2262 76.94 7394.32 6.7

5 2.07795 71.81 7165.06 8.1

6 2.68009 92.62 8595.98 6.5

7 0.99171 34.27 5647.33 7.5

8 2.78978 96.41 9231.48 7.4

9 1.69615 58.62 7885.59 6.8

10 2.62823 90.83 8061.37 6.1

11 2.06653 71.42 7720.39 6.9

Mean 2.188941818 75.64818182 7729.225455 6.936363636

tandard Deviatio 0.526262841 18.23268983 1385.327169 0.578399044

Minimum 0.99171 34.27 5405.69 6.1

Maximum 2.8092 97.09 10504.47 8.1

Static Bending results

Figure(58): table of results for 11 samples of bending tests

-20

0

20

40

60

80

100

0 5000 10000 15000 20000 25000 30000 35000 40000

F l e x u r e s t r e s s ( M p a )

Flexure strain (%)* 10*-4

Sample 1


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-20

0

20

40

60

80

100

120

0 5000 10000 15000 20000 25000 30000 35000


Flexure strain (*10^-4) %

Sample 2

-10

0

10

20

30

40

50

60

70

0 10000 20000 30000 40000 50000 60000

F l e x u

r e s t r e s s ( M p a )

flexure strain

Sample 3

-10

0

10

20

30

40

50

60

7080

90

0 5000 10000 15000 20000 25000 30000 35000 40000 45000


Flexure strain *10^-4 (%)

Sample 4


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-10

0

10

20

30

40

5060

70

80

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

F l e x u r e s t r e s s

Flexure strain

Sample 5

0

10

2030

40

50

60

70

80

90

100

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05

F l e

x u r e s t r e s s ( M P a )

Flexure strain (mm/mm)

Sample 6

-5

0

5

10

15

20

25

30

35

40

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 F l e x u r e s t r e s s ( M P a )

strain (mm/mm)

Sample 7


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Figure (59): the graphs between flexure stress and strain of the five samples

0

20

40

60

80100

120

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

F l e x u r e s t r e s s ( M P

a )

Strain (mm/mm)

Sample 8

-10

0

10

20

30

40

50

60

70

80

90

100

0 0.005 0.01 0.015 0.02 0.025 0.03

F l e x u

r e s t r e s s ( M P a )

Strain (mm/mm)

Sample 9

0

10

20

30

40

50

6070

80

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

F l e x u r e s t r e s s ( M P a )

Strain (mm/mm)

Sample 10


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Description of static bending failure:

Static bending (flexural) failures shall be classified in accordance with the appearance of the

fractured surface and the manner in which the failure develops. There were two types of the failure

types that were described in the following figure and all of the sample fractures were photographed

and four of them are cross grain failure while only one is splintering type.

Figure (60): all the shape failure of the wood

Sample (1) Sample (2)


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Sample (3) Sample (4)

Sample (5)

Figure (61): failure shapes of the five samples


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Designing a Wooden Girder:

The initial phase of our research is to classify Casuarina wood species in Egypt in terms of

all of its physical and mechanical properties. Afterwards the secondary objective of our research

includes a designing phase, in specific designing a wooden girder which is primarily used for wall

and slab formworks in the construction field. Of course the success of this design all depends on

the final properties or characteristics achieved for the Casuarina Wood.

Background:

The design of the girder will imitate the design of an already existing girder from PERI

Formwork Systems; in particular we will adopt the design of model GT 24 with a length of 4.2

meters. The function of this girder is to simply provide efficient formwork for walls and slabs at a

cost effective state. GT 24 is strong enough to cover the formwork of all types of walls in the

construction industry, from ordinary residential walls to retaining walls, reaching up to 18 meters

using only 1 panel. In terms of slabs it allows formwork for large spans, and as a result the use of

GT-24 will tend to reduce the number of components used in a formwork system, which leads toless labor requirements, and is more cost effective.

Figure (62) Peri girders model GT24 L = 4.2 m

Figure (63) the basic dimension of the girder beam GT24 with L = 4.2m


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Objective:

The constructed model from Casuarina wood was tested under binding test. The outcomes

of this test were compared to other types of wood used in similar girder beams to see if it worth it

to start exploring Casurina as a new material in construction industry. The significance of designing

such a model from Casuarina wood is really important; if successful we would have overcome a

groundbreaking achievement in the formwork industry due to the major cost savings between our

model and PERI's; the customers would be charged a third of what PERI industries are charging.

Procedures:

The methodology that was followed in order to produce such a design, is first analyze our

properties and design figures, place the design on AutoCad as in Figure() then transfer the design

to SAP in order to test the functioning of such a model. Afterwards a simple model of the GT 24

girder was constructed with some deviations due limitations in workshops and in available wood.

Then it was tested and the results were analyzed.

Figure(64): a simple design for a girder beam with some differences from G24 design


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The building process of the wooden truss system is quite simple which may be summarized

in four to five steps.1First we must acquire the wooden logs at the lengths needed according to the

design parameters. Next we saw off the bark from the logs Figure(65), during this process lots of

material is wasted due to the technicalities in sawing off bark from wooden logs. Afterwards the

expert will3 smoothen out the surfaces (clean up) of the long beams created. The smoothening

surface is an important step especially in terms of formwork construction. Formworks arerequired to contain a non-rough surface due the fact that concrete may stick to the surfaces of the

wooden formworks during the pouring and drying processes. Therefore the carpenter will

smoothen and clean the surface from any irregularities.

After we smoothen and clean the surfaces of the wooden beams, the expert will detail or

cut it in the specified dimension of the design. Keep in mind that during the initial cutting stages

the remainders left over may be used to create the smaller members of the truss only if they are

sufficient for use. After wards the most important part comes which is the placement of the pieces

together. The method of putting the pieces together is sincerely significant in terms of the overall

use of the truss, in specific the design of the joints.

Figure (65): sowing the logs and smoothing the surface for a Casuarina Tree

Figure (66): the final product of a truss after lacing the member in its joints


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Truss Load Testing:

The truss was built and then the next step was to test the sustainability or strength of the

system. The American University of Cairo has a unique testing machine which was suitable of

performing such a test with the use of a hydraulic jack system fixed to a steel frame as shown in

figure(67).The truss was supported on two rollers with a span of 180 cm that pointed in Figure(67). A concentrated load was added to the truss approximately at the center of it as shown above.

Afterwards the load is applied until failure is reached. The device Shown in Figure (68) on the

bottom “the Linear Variable Differential Transformer” is working as a dial gage to measure the

deformation of the system during loading and unloading. Some of the joints were not placed

accurately over the rollers like in figure (69) below however the load from the jack were exactly

over one of the joints.

Figure (67): the truss is supported on Figure (68): the Linear Variable

two rollers to resist the load produced Differential Transformer

by the hydraulic jack

Figure (69): some joints were not placed over the supporter exactly


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Result and analysis:

The results of our test were as follows, the maximum load was 746.91 kgf, the deflection at

maximum load is 19.81 mm, and with a deformation recovery of 13.81 mm.

The curve below is a representation of the relationship of the load kgf) vs deformation mm).

Figure (70): Loading Vs. deformation curve for the wooden truss constructed from Casuarina

As we can realize the shape and results of the curve is somewhat unusual however we need

to keep in mind that the wood in the truss had a moisture content of nearly 70% and the

dimensions of the truss system used in this test are different than the theoretical design (theoretical

design is larger). The maximum load was somewhat low compared to values of other truss

systems, however we had relatively high moisture content and the configuration of the joints were

somewhat sloppy. These two factors significantly affected the strength of the truss, if it where drier

(12% moisture content) and had improved joint designs the maximum load the truss would sustain

would be doubled or even higher. In addition there is a permanent deformation of 6.5 mm.

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25

L o a d ( k g f )

Deformation (mm)

Note: PermanentDeformation = 6.5mm


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During the testing of the truss a certain shape of failure appeared. In the Figure (), the

actual shape of failure is evident. The shape of failure here is more of a bending failure rather

than compression, as it is expected. As well as the most of the load is carried on the top chord

because the truss failed to behave as a truss under the load once the members were pulled out of

its joints. As a result, the top chord were carrying the load a lone with some members hanging on it

and almost disconnected to the bottom chord which supposed to have the failure earlier as tensionfailure. Because of the tension members being vulnerable like that, it supposed to be investigated

in the design of the joints thoroughly in order to prevent a fault such as this to occur in the future.

As well as there is an advantage to the failure of the truss, it’s that the wood did not attempt to

crack in an explosive manner (fragments of wood did not fly all over the place), instead the wood

stayed together and that is due to the high ductility of the material itself and the high water content

of the wood.

Figure (71): the failure in the top chord of the truss after loading it.

Figure (72): Tension members were pulled out of the joints

Initial shape of failure

at top chord


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Joints:

There are many factors that may affect the strength of a truss such as knots, slope of grain,

shrinkage fissures, and other defects (such as bacterial and insects infestation). The joints are yet

one of the most important factors of any system since they have a direct effect on the mechanical

of the system. Unfortunately, the joints of the truss are the factor that have not been studiedthoroughly yet by our research team due to certain time constraints, and that is why our results

varied from others. However in reference to the Peri GT-24 model we were able to improvise on

the details of our joint design. We attempted to have a wood on wood connection just like Peri,

but due to the company's secret of trade, they trademarked (copyrighted) their method of design

for such trusses. So in our system the joints were done in the way as shown in the figures below.

In one joint there will be two heads faced opposite of each other fitting into a joint. They will be

basically fixed in with their dimensions with the help of some sort of super glue. The photo below

will show an actual image of our truss joint.

As shown in the image above the joint consists of a wood to wood connection, the width of the

joint is 15 cm where the width of one member head is 7.5 cm and width 2 cm. The tongue

("lissan") or key of the member is the part that enters the members. Keep in mind that the

construction of the truss was done at a basic wood workshop; therefore we were absent to some of

the engineering expertise needed at the workshop (other than our engineering knowledge). Incomparison to Peri's GT 24 model, both our joints and theirs are composed of wood to wood joint

basis, however the specific design of Peri's joints are different as shown in the figure below.

As shown in the figure above is the finger joint configuration Peri uses in their GT-24 model. As

mentioned before the details to their joint construction is rather classified and may not be

disclosed to any unfamiliar member to the company.

Member head within joint

7.5 cm

Peri GT-24 Joint configuration

(finger joints)


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Sap Analysis:

After testing the girder model, and recording the maximum load till failure 746 Kgf, a Sap

analysis was constructed using the actual dimensions of the girder and applying same maximum

load is withstood.

When analyzing the model, two critical conditions were tested. The first is the girder actingas truss by releasing the moment at the nodes but that was unstable and showed that it was crucial

to have moment and explains why Peri opted for a girder instead of a truss. The second critical

condition which was tried is using total fixation at the nodes, this is a better representative of the

girder model since it accounts for moment at the nodes. In addition the members of the girder

penetrate the upper and bottom chords a significant distance of around 70% of their total depth

thus explaining how the model is very much closer to being a girder than a truss.

Figure(): the load analysis on the members and top and bottom chords.

The Figure above shows the normal forces in the members and chords of the girder. The

distance between the roller and the hinged was 180 Cm which is exactly similar to the testing

conditions previously done. The length from roller and hinge to the end of the girder is 40cm on

each side, also similar to the testing conditions. The load was placed in the same place as girder

tested specifically at intersection of the two inclined members at upper chord's midpoint.

Knowing that our girder model failed due to tension members failing to work because they weren’t held properly by the connections at the nodes, we were looking for data from the sap

analysis to proof our theory.


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The following table summarizes our findings.

The maximum stress, tension and compression on the members and chords was calculated

and compared with the maximum stress of Casuarina wood we already found in our previously

stated tests.

Knowing that the girder was under compression and tension parallel, their corresponding

test results were compared with the maximum stress from the sap analysis.

-Casuarina wood could have carried up to 42.3Mpa in compression parallel but failed at

2.3Mpa in members and 1.63Mpa in upper chord!

-Casuarina wood could have carried up to 93Mpa in the tension parallel but failed at

1.6Mpa in members and 1.63 in the lower chord. So these results confirm our theory, that ourgirder failed at 746kgf under maximum stress that could have been carried easily by Casuarina

wood but due to the fact that the connections at the nodes weren’t designed correctly they failed

the girder and exposed the upper chord to withstand the load alone which was like witnessing a

bending test.

Maximum

Stress

Girder (Sap

Analysis)

Material Testing

Compression Parallel

(Member)

2.3 Mpa 42.3Mpa

Compression Parallel

(Upper Chord)

1.63 Mpa 42.3Mpa

Tension Parallel

(Member)

1.6 Mpa 93Mpa

Tension Parallel to

grain (Lower chord)

1.63 Mpa 93Mpa


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Outcomes and comparison

This figure below is a simple comparison between Casuarina wood and the most commercially

important wood in Egypt like Oak wood and pine Wood (as known in the market El Aro and ElMosky) and Dougles fire wood which is very popular as in USA for formwork industry. The

comparison was in mechanical and physical properties and the prices per m3 in Egypt.

It is clear in the comparison that almost Casaurina lies the second after white Oak in all

strengths except in modulus of elasticity lies the third. On the other hand, it is considered one

of the cheapest ever compared to its natural strength with other wood that are as strong as

Casuarina.

Economics of Casuarina Model:

Engineers always attempt to construct at the lowest cost but at the same time maintain a

certain acceptable value of quality. In formworks the there are two main parts that affect its

overall costs, first is the actual cost of the formwork system used, second is the labor cost for

formwork installation.

Our model is based on the Casuarina wood grown in Egypt. The price of 1m3 of Casuarina wood

in Egypt reaches up to 250 LE/m3 in comparison the Pine wood used in Peri's Gt24 is 1800

LE/m3.

In terms of the cost of the amount of wood used in a single truss, our model also tends to

performs better than Peri's GT 24. The cost for the amount of wood used in a single truss

reaches up to 50-60 LE, and then include the cost of technical operations and chemical

treatment, the overall cost of to build a single truss is 120 LE/truss. Peri offers the price of a

single truss at about 1,500LE/truss. Keep in mind that if our model is produced in large

quantities’ the prices of single truss will be even lower due to the mass production rates. In

addition that with the use of such systems during the formwork phases of construction, there

will be reduction in the cost of custom formworks. This is because of the reduced amount of

labor costs required to use such formworks at any construction site.

As you can see the price differences between our model and Peri's is quite significant, which

makes it worthwhile for us to pursue our research and making it the best in its field of use

(formwork).

Type of

wood

Moisture

content

Specific

Gravity

Modulus

of

elasticity(Mpa)

compressive

strength

parallel(Mpa)

Compression

perpendicula

r (Mpa)

Tensile

strength

parallel(Mpa)

Tensile

strength

perpendicular (Mpa)

Price

(LE/ton)

Casurina 12% 0.45 7729.2 42.3 5.64 93.2 4.25 250

Oak Red 12% 0.61 11300 23.90 4.9 77.9 5.2 6000

Oak White 12% 0.68 12300 51.3 7.4 112.4 5.3 7000

Pine White 12% 0.34 6800 16.8 1.5 73 2.1 1800

ine Lodgepol 12% 0.4 7400 18 1.7 84 2 2000

Pine Jack 12% 0.38 8500 20.3 2.1 63 2.9 1200

Douglas Fir 12% 0.45 13,400 49.3 5.5 75.8 2.3


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Following example taken from Sisterzone.com it compares tensile strength to

compressive strength of Balsa wood.

DensityCompressive

Strength (lb/in²)

Tensile

Strength

(lb/in )

Tensile/Compressive Strength

Ratio

Low 680 1100 1.617647

Medium 1750 2890 1.651429

High 2830 4670 1.650177

Clearly, balsa wood is 60% stronger under tension than under compression for all densities.

So, what possible use is this? Well, recall that the compressive and tensile forces in the top and

bottom chords are equal (each are 60 pounds), as are their cross sectional areas (about 7/32 square

inches for each chord and 2 x 7/32 = 14/32 for the left and right chords together). Let's compute

the failure points for two cases, one where the lighter material is on the top, and the other where it

is on the bottom.

Chord

Case 1:

Force needed to fail with low

density on top chord, medium

density on bottom

Case 2:

Force needed to fail with medium

density on top chord, low density on

bottom

top 14/32 * 680


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The table below shows simple comparison between GT24 and Casaurina model

Category Peri GT-24 TK-NO-11 (our model)

Weight 2.5kg/m 7.5kg/m 58% M.C (3.84kg/m12% M.C )

Joint

Configuration

Cost 1500 LE/unit 80+ durability treatment(50)=125LE/turss

Permissible

Bending

Moment

7k Nm 3.35 kNm

Conclusion Failed due to connection errors, since

members could have carried more stress.

As seen tension chords were pulled

before major failure was seen.


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Recommendation:

Drying the wood

Wood drying is a process in which we dry the wood to reduce its moisture content. This is done because when wood is used in construction it will absorb or desorbs moisture until it reaches

equilibrium with the surroundings. This causes unequal shrinkage in the wood which causes

damage to the wood if it dries quickly and reaches equilibrium fast. The equilibration must be

controlled to prevent damage.

Ways to dry the woodThe two most economical ways to dry the wood is by either Kiln dryring or Air drying. Correct

exposure of lumber to the outside air can reduce moisture content to 12 – 19 percent; At this

moisture content, The wood is suitable for many construction uses and applications.

Air drying

When air drying we mainly make stacks of sawn timber on raised foundations in a dry

place. Depending on climatic conditions the rate of drying will vary. It also will depend

on the air movement and exposure to the wind. The rate of moisture loss increase if the

flow of air increases and vice versa.The rate of loss of moisture can be controlled by

coating the planks ordinary mineral oil .Coating the ends of logs with oil or thick paint,

improves their quality upon drying. Wrapping logs in a way which will allow some

movement of moisture will also work provided. But before doing this the wood is first

treated against infection of Fungus by coating in gasoline or oil. When we started air

drying the wood we just put it in the desert and assumed the hot climate is enough.

Later, in order to increase the rate we arranged the wood in a way to have larger areasexposed to the air and sun.

Figure (): Air Drying by exposing larger areas of the wood to the surroundings


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Kiln drying

Kiln drying consists basically of introducing heat. This may be using natural gas ,

electricity or even through steam-heated heat exchangers. Nowadays Solar heated kilns

are also used. During heating we should control temperature, relative humidity and air

movement and circulation to achieve effective drying. Therfore, the timber is stacked in

chambers or drying kilns which are fitted with equipment that manipulates and controls

the temperature and the relative humidity of air and its circulation rate. We used kiln

drying method in the school’s oven and used a temperature of 50-70 C which is

effective for both dring the wood and killing any fungi that may grow on it.

Figure (): Drying Chambers for wood

Figure (): conventional drying chamber for wood


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Joints problem:

Other methods of truss joint systems are available and may be induced in our own truss, such

as using steel plates and nails. One method is the gang-nailed system.

Figure (): steel plates used as a way to fasten the joints more

"A Gang-Nail connector is a steel plate with a collection of spikes or nails projecting from one face. Thespikes or teeth are formed by punching slots in steel but leaving one end of the plug connected to thesheet. The teeth are then formed so they project at right angles to the plate. During this process theteeth are shaped to produce a rigid projection. When the teeth of a connector plate are pressed intotimber laid end to end, the plate welds them together by forming a Gang-Nail joint. Connectors are

always used in pairs with identical plates pressed into both faces of the joint." ()

In the image below is a representation of the steel connector on the truss system.

Figure (): a steel plate nailed in a joint


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Woods failure due to improper cutting:

It was noticed that when cutting wooden planks from a log, there arises a problem in

how to most effectively cut the planks to get the most pieces of planks. It was

discovered that the samples, that had the center of the log somewhere in the samplesplit and cracked near to that center point. The possible explanation is that the

center point of the log, has the most moisture content and dries slower than the parts

further away from that center thus due to difference in shrinkage rates the samples

would crack and splits example of our samples splitting due to that weak point.

That’s w hy when we researched more into it, we found out that wood is generally cut

in a certain fashion to make sure the center point doesn’t lie somewhere inside a

wooden plank; see figure below.

Also we found out that a plank's grain pattern can be categorized by where that plank

was cut from the log.

"The quarter sawn is the most stable, and usually gives a straight grain pattern down the

length of the plank. The flat sawn will usually cup up on the ends as it dries (as shown in

this location), and will have a more pronounced grain down its length. The rift cut will

come out somewhere in the middle."


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References:

Species Profiles for Pacific Island Agroforestry: Casuarina equisetifolia :

http://agroforestry.net/tti/Casuarina-she-oak.pdf

NFT Highlights: ( A quick guide to useful nitrogen fixing trees from around the world)

http://www.winrock.org/fnrm/factnet/factpub/FACTSH/Casuarina_sp.html

The wood explorer:

http://www.thewoodexplorer.com/maindata/we267.html

Why Build with Wood?

http://www.wood-works.org/NR/rdonlyres/E681783E-AAD5-4F54-B4BF-

853D10489E2B/0/WhyBuildwithWood.pdf

ASTM tests:

ASTM D143 - 09 Standard Test Methods for Small Clear Specimens of Timber

ASTM D2395 -09 Test Methods for Specific Gravity of Wood and Wood-Based

Materials

ASTM D4442 -09 Test Methods for Direct Moisture Content Measurement of Wood

and Wood-Base Materials

ASTM D2915 - 09 Practice for Sampling and Data-Analysis for Structural Wood and

Wood-Based Products

GT 24 Formwork Girder:

http://www.wiehahn.co.za/upload/uploads/35/GT-VT_Girders_original.pdf

Blasa Wood comparsion: http://www.sisterzone.com/Adv-Material%20Analysis.htm
http://agroforestry.net/tti/Casuarina-she-oak.pdfhttp://agroforestry.net/tti/Casuarina-she-oak.pdfhttp://www.winrock.org/fnrm/factnet/factpub/FACTSH/Casuarina_sp.htmlhttp://www.winrock.org/fnrm/factnet/factpub/FACTSH/Casuarina_sp.htmlhttp://www.thewoodexplorer.com/maindata/we267.htmlhttp://www.thewoodexplorer.com/maindata/we267.htmlhttp://www.wood-works.org/NR/rdonlyres/E681783E-AAD5-4F54-B4BF-853D10489E2B/0/WhyBuildwithWood.pdfhttp://www.wood-works.org/NR/rdonlyres/E681783E-AAD5-4F54-B4BF-853D10489E2B/0/WhyBuildwithWood.pdfhttp://www.wood-works.org/NR/rdonlyres/E681783E-AAD5-4F54-B4BF-853D10489E2B/0/WhyBuildwithWood.pdfhttp://www.astm.org/Sta

Documents

Thesis I Final Report (Casurina Wood)