FORCES IN PLANE TRUSS

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FORCES IN PLANE TRUSS

EXPERIMENT 4

DKA 5A

OBJECTIVE :

To determine the forces in members of a plane truss.

APPARATUS :

1) A Warren truss with members having a force gauge fixed to it.

2) A screw jack for applying load to the truss.

Dial gauge readings : 1 Division = 5N

POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH | C4003 CIVIL ENGINEERING LAB

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EXPERIMENT 4

DKA 5A

PROCEDURE :

1) Place one end of the plane truss on the roller support and the other on the pin

support (please ensure that the centre of th joint is located on the knife edge

and at the centre of the roller).

2) Loosen the screw jack so that the truss is free from the applied load.

3) Zerro the force gauge readings on the members and the screw jack.

4) Turn the screw jack handle to apply loads in the downward direction.

5) Record the magnitude of the applied load and the force gauge readings.

6) Increase the magnitude of the applied load and for each load increment

records the force gauge readings.

7) Measure the horizontal and vertical length of the frame in order to calculate

the theoretical forces.


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EXPERIMENT 4

DKA 5A

Applied Load(N)

Force in Member AB Force in Member BE

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

1 5.50 0.28 -0.58 11.0 0.55 0.58

2 17.50 0.88 -1.15 22.0 1.10 1.15

3 29.00 1.45 -1.73 34.0 1.70 1.73

4 42.00 2.10 -2.31 45.0 2.25 2.31

5 54.00 2.70 -2.89 57.0 2.85 2.89

Applied Load(N)

Force in Member CE Force in Member CD

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

1 11.00 0.55 0.32 12.50 0.63 -0.58

2 22.00 1.10 0.64 25.00 1.25 -1.15

3 32.00 1.60 0.92 37.50 1.88 -1.73

4 43.00 2.15 1.24 50.00 2.50 -2.31

5 46.00 2.30 1.33 62.00 3.10 -2.89


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EXPERIMENT 4

DKA 5A

Applied Load(N)

Force in Member EA Force in Member ED

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

1 5.00 0.25 0.07 6.00 0.30 0.07

2 10.00 0.50 0.14 12.00 0.60 0.14

3 14.00 0.70 0.20 18.00 0.90 0.20

4 20.00 1.00 0.29 25.00 1.25 0.29

5 25.00 1.25 0.36 30.00 1.50 0.36

Applied Load(N)

Force in Member CB

Dial gauge

reading (div)

Force (Exp.)

(N)

Force (Theory)

(N)

FAB = -w 2 sin 60

FAE = w cos 60 2 sin 60

FBE = w 2 sin 60

FBC = -w cos 60 2 sin 60

1 11.00 0.55 -0.58

2 23.00 1.15 -1.15

3 35.00 1.75 -1.73

4 47.00 2.35 -2.31

5 59.00 2.95 -2.89

1) Using the data in the table above, plot the graph of force in the members verses

the applied load for the experimental and theoretical case.

2) Determine the percentage error.

Percentage Error = Theoretical Slope – Experiment Slope x 100

Theoretical Slope


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EXPERIMENT 4

DKA 5A

Member Theoretical Slope (N) Experiment Slope (N) Percentage Error (%)

AB 8.66 7.41 14

BE 8.66 8.45 2

CE 4.45 7.70 73

CD 8.66 9.36 8

EA 1.06 3.70 25

ED 1.06 4.55 30

CB 8.66 8.75 1


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EXPERIMENT 4

DKA 5A

DISCUSSION :

1) State the relationship between the applied load and the force in the members.

When the truss is loaded with a force W Newton, as in the Figure 5.3,

the truss will adjust itself to achive a more stable situation balanced. When this

condition is reached, the frame is said to be in equilibrium. Equilibrium is

obtained as a whole means that each member is in a state of balance. If not, it

would have been members of the moves kesatu a more stable position.

Assume that one of the members, the members of the DE, is in

equilibrium. External force of magnitude P acting at point D in the DE must be

balanced by a force with a magnitude equal to P, but in the ED at the point E, as

shown in the Figure 5.4(a). In this way the members of DE can be balanced.


Figure 5.3

Figure 5.4

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EXPERIMENT 4

DKA 5A

Because members of the DE is in equilibrium, the point D itself is also

in equilibrium. Therefore, if the split between the point D to point E, as shown in

Figure 5.4 (b) force at every point has a magnitude P in the direction opposite to

the direction of external forces earlier. Thus, the force in the member acting

against the direction of DE external force is applied,

and must have the same magnitude as the external force, see Figure 5.4 (c). For

members who have this compressive force, the internal force to the point of

connection.

At the same time, if we look at the members of the CD, an external

force which suffered a tensile force, as shown in Figure 5.5 (a), while the internal

forces are shown in Figure 5.5 (b). Thus, for members who experience a tensile

force, the internal forces from the point of connection.


Figure 5.5

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EXPERIMENT 4

DKA 5A

2) State the possible factors that might have influenced your result and means of

overcoming it.

The reading for the apparatus in the experiment is not accuracy.

The person that held for the experiment is not enough experience and

knowlange obout the experiment.

Reading error when taking data because the eyeposition..

Area condition and surrounding factor such as heavy wind, in accurate

measurement..

CONCLUSION :

State the conclusion obtained from the experiment

When the load is applied to the truss, the foce in each of members of a plan truss will

have a different reading of force.

REFERENCES

1) Zulkifli Md. Salleh and Saiful Anuar A. Rahim 1991. Pengenalan Analisis Struktur,

Dewan Bahasa dan Pustaka. *86


FORCES IN PLANE TRUSS

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