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Timber stuffs are consumed by a big scope of industries, a widely used stuff in building either structurally such as roof trusses, gear wheels, boats, furniture, and not structurally such as signal poles, doors and window frames etc.It is merely define as a low denseness, cellular, polymeric composite stuff. Timber is a merchandise of nature that is cut and machined from trees.It can non be manufactured to a peculiar specification instead the best usage has to be made of the stuffs already produced though it is possible to choose from broad scope available with the most desirable scope of belongingss ( Dinwoodie j. M ) . This belongings comprises of physical and mechanical belongingss such as strength and wet content, etc. Timber used for structural intents demands to hold dependable strength belongingss so that it can defy the scope of forces, or ‘stresses ‘ , that will move on it in the standing construction. Three point flexing trial of little clears ( little and knot free ) and trial of 4 by 2 Structural batting ( large with knots ) will be used to find the strength and failure rate of six selected samples of wood for each method. The research undertaking is carried out utilizing the information in BS373:1957 and BS EN 408:2003 for the trial of lumbers.

2 THREE POINT BENDING TEST OF SMALL CLEARS

This was originally used for the derivation of working emphasiss for lumber but was subsequently superseded by structural-size lumber in mid-1970s.it is still valid for qualifying new lumbers and for rigorous academic comparism of wood from different species because of its little knot-free heterosexual grained perfect trial pieces which represent the maximal quality of wood that can be obtained.

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A Undertaking 1: Procedure Results & A ; Classify Failure Mode

From the information contained in the Excel spread sheet tabular arraies ( downloadable from Web CT ) determine in concurrence Appendix A and where appropriate information from BS373:1957:

1. The Modulus of Elasticity ( MOE )

2. Contained in Figure 2.1 are a choice of exposure taken of the trial specimens after proving sort their failure manners ( Figure 2.2 ) and do any relevant remarks sing the burden supplanting curves.

3. Remark on your consequences and where appropriate do mention to allow literature resources.

Solution

The Modulus of Elasticity ( MOE )

Using

Where:

Em, app = Apparent modulus of snap

Fmax = maximal force

F1, F2 = burden values in excel sheet

W1, w2 = matching displacement values of f1, f2 in excel sheet

cubic decimeter = 21952000000 millimeter

I = 13333.33

B = 20 millimeter

vitamin D = 20 millimeter

SEE TABLE FOR RESULTS BELOW

Signal-to-noise ratio

Fmax ( N )

F1 ( N )

F2 ( N )

W1 ( MM )

W2 ( MM )

F2-F1

W2-W1

Em, app

1

1.31E+03

1.31E+02

5.22E+02

6.45E+01

2.20E+00

3.92E+02

1.55E+00

3.71E+15

2

1.56E+03

1.56E+02

6.25E+02

6.15E+01

2.18E+00

4.69E+02

1.57E+00

1.02E+07

3

1.59E+03

1.59E+02

6.36E+02

6.52E+01

2.20E+00

4.77E+02

1.55E+00

1.06E+07

4

1.56E+03

1.56E+02

6.24E+02

5.79E+01

2.11E+00

4.68E+02

1.53E+00

1.05E+07

5

1.03E+03

1.03E+02

4.11E+02

6.04E+01

2.07E+00

3.08E+02

1.47E+00

7.20E+06

6

1.40E+03

1.40E+02

5.59E+02

7.38E+01

2.66E+00

4.19E+02

1.92E+00

7.48E+06

2 ( a ) Modes Of failure for little clear in the samples images ( see appendix )

Horizontal shear: This occurs most when there are disconnected alterations in the growing zones.

Seceding tenseness: It is as a consequence of low wet content

Seceding tenseness

Brash tenseness: This usually occur when there is compaction or decay. It shows the presence of unnatural molecular construction.

Cross grain tenseness: This is as a consequence of grain orientation in wood and this consequence in tenseness failure.

Simple tenseness and horizontal shear

2 ( B ) Comments sing the burden supplanting curve

SMALL CLEAR 1 GRAPH

SMALL CLEAR 2 GRAPHS

SMALL CLEAR 3 GRAPHS

SMALL CLEAR 4 GRAPHS

SMALL CLEAR 5 GRAPHS

SMALL CLEAR 6 GRAPHS

Notice that at the beginning of the trial, the curve shows a little contrary curvature.This is as a consequence of local suppression of unwilled high athleticss as the terminals of the specimen becomes seated on the platen of the testing machine.

To rectify for this, the consecutive line part of the curve may be extrapolated downwards to turn up an adjusted zero grade MTP Construction ) .

From the curve, samples has different ultimate strength and supplanting at same burden rate which may be as a consequence of internal components of the samples.

The stuffs exhibits different types of failure.

( 3 ) Remark on your consequences

Each sample average value is capable to some grade of mistake, and little differences between the average values of species up to about 10 % are normally within the possible scope of mistake of the values and may hold no practical significance. When doing these comparism that under certain conditions where strength is one of the principal demands, there may be other factors which will besides act upon the pick of a lumber for a peculiar intent. Factors such as ability to defy fungous onslaught, stableness with alterations in humidness and temperature have to be considered. ( MTP building, The strength belongingss of lumber, 1974 )

3 Trial OF 4 BY 2 STRUCUTRAL BATTENS

B Task 2: Procedure Results & A ; Classify Failure Mode

From the information contained in the Excel spread sheet tabular arraies ( downloadable from Web CT ) determine in concurrence Appendix A and where appropriate information from BS373:1957:

1. The Local and Global Modulus of Elasticity ( MoE )

2. The Modulus of Rupture ( MoR )

3. Contained in Figure 3.2 are a choice of exposure taken of the trial specimens after proving sort their failure manners ( Figure 3.3 ) and do remarks relative to the determined MoE, MoR and load supplanting curves.

4. Remark on your consequences and where appropriate do mention to allow literature

resources.

Solution

( 1a ) The local and Global Modulus of Elasticity ( MOE )

Using the Equation for Local MOE

Where:

F2-F1 is an increase of burden in the additive part of the load-deflection curve ( N ) ,

wc2-wc1 is an increase of warp matching to F2-F1 ( millimeter ) ,

I is the 2nd minute of country of the batting ( I=bd3/12 ) ,

a and degree Celsius are the span distances shown in Figure 3.1

l1 is the clear span ( millimeter ) =5h

s = 1800

B = 50

vitamin D = 100

L = 600

degree Celsiuss = 500

H = 100

T = 0.003hm/s

a = 600

I = 4166666.67

( 1b ) Global Modulus of snap

Where:

s is the span distance between supports,

ws2-ws1 is an increase of warp matching to F2-F1 ( millimeter ) .

Bending strength ( MOR ) is calculated utilizing the undermentioned equation:

( 2 ) MOR

Using the Equation

Where:

Fmax is the maximal force applied to the batting.

SEE TABLE FOR RESULTS BELOW

Signal-to-noise ratio

Fmax

F1 ( N )

F2 ( N )

W1 ( MM )

W2 ( MM )

F2-F1

W2-W1

Bat 1

1.73E+04

1.73E+03

6.92E+03

3.32E+00

1.32E+01

5.19E+03

9.92E+00

Bat 2

1.52E+04

1.52E+03

6.09E+03

3.21E+00

1.30E+01

4.57E+03

9.77E+00

Bat 3

1.48E+04

1.48E+03

5.93E+03

2.74E+00

1.09E+01

4.45E+03

8.14E+00

Bat 4

1.05E+04

1.05E+03

4.21E+03

2.38E+00

9.74E+00

3.16E+03

7.36E+00

Bat 5

1.81E+04

1.81E+03

7.23E+03

3.85E+00

1.47E+01

5.42E+03

1.09E+01

Bat 6

1.48E+04

1.48E+03

5.92E+03

2.62E+00

1.04E+01

4.44E+03

7.76E+00

Signal-to-noise ratio

MOEL

MOEG

MOR

Batten 1

2.35E+03

1.24E+04

1.25E+02

Batten 2

2.11E+03

1.11E+04

1.10E+02

Batten 3

2.46E+03

1.30E+04

1.07E+02

Batten 4

1.93E+03

1.02E+04

7.59E+01

Batten 5

2.25E+03

1.19E+04

1.30E+02

Batten 6

2.57E+03

1.36E+04

1.06E+02

( 3a ) Manners of failure for Batten in the sample images ( see appendix )

a ) Compaction near a knot

B ) Diagonal tenseness

degree Celsius ) Diagonal tenseness

vitamin D ) Compaction near a knot

vitamin E ) Localised cross-grain tenseness

degree Fahrenheit ) Compaction near a knot

This failure modes in batting is ever as a consequence of defects in the wood like knots

( 3b ) BATTEN 1 GRAPH

BATTEN 2 GRAPH

BATTEN 3 GRAPH

BATTEN 4 GRAPH

BATTEN 5 GRAPH

BATTEN 6 GRAPH

Modulus of snap and modulus of rupture in the supplanting curve are about the same.

Modulus of snap: Initial consecutive line portion of the burden – supplanting curve. MOE can be found from the flexing trial, but its value will differ somewhat from that found from the compaction trial. The ground is that the mensural beam warp are affected by shear strains every bit good as by flexural strains. The additive relationship between emphasis and strain within the elastic scope of a stuff, supplying an indicant of stiffness.

Modulus of Rupture: The highest emphasiss in the outermost fibers of the wood when the beam interruptions under the influence of a burden.

The modulus of rupture is the value of mc/I which would be compute utilizing the bending minute caused by the ultimate burden. Modulus of rupture is non the value of extreme-fibre bending emphasis at failure. Bending emphasiss under elastic conditions vary as a consecutive line.

( 4 ) Remark on consequences

TheMean value derived from structural size informations is low.

4 Decision

The highest strength of clear strength grained lumber is in tenseness along the grain, whereas the lowest is in tenseness perpendicular to the grain.Tensile strength of structural size is lower than the compaction strength while in little clear tensile strength is higher than the compaction strength, this is as a consequence of knots and associated deformed grains in structural size. Normal distribution curve fits the information from little clear trial piece better than informations from structural size.

Stiffness ( Modulus of Elasticity ) The values obtained in any finding of the belongingss of lumber depend upon the trial methods used. It is

hence desirable that these methods be standardized so that consequences from different trial Centres can be correlated.

Furthermore, with the acceptance of bound province design and with the development of both ocular and machine emphasis scaling, attending will be progressively centred on the finding and monitoring of the strength belongingss and variableness of lumber in structural sizes. Again, this can be more efficaciously undertaken if the basic informations are defined and obtained under the same conditions.

Timber type and grain formation etc, are really of import factor in both trial method because the have effects to the general result of the trial consequence.

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