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.
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.
Applied Load
(N)
Force in Member AB Force in Member BE Dial gauge readin g (div) Force (Exp.) (N) Force (Theor y) (N) Dial gauge readin g (div) Force (Exp.) (N) Force (Theor y) (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
(N) g (div) (N) (N) g (div) (N) (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 Applied Load (N)
Force in Member EA Force in Member ED Dial gauge readin g (div) Force (Exp.) (N) Force (Theor y) (N) Dial gauge readin g (div) Force (Exp.) (N) Force (Theor y) (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
Applied Load (N) Force in Member CB Dial gauge readin g (div) Force (Exp.) (N) Force (Theor y) (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.
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
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
Figure 5.3
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.
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,
Figure 5.4
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
• 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
