OBJECTIVE
The objective due to experiment of reaction of a continuous beam is ;-
1) To determine the reaction of a two-span continuous beam. 2) To determine either by doing an experiment or by using a formula will get more accurate answer. 3) To understand the concept of continuous beam. 4) To finish by the time frame given. 5) To memorise the formula given.
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INTRODUCTION
A continuous beam is a statically indeterminate multi span beam on hinged support. The end spans may be cantilever, may be freely supported or fixed supported. At least one of the supports of a continuous beam must be able to develop a reaction along the beam axis. The statically determinate primary system may be obtained by elimination of constraints considered as redundant. The most intuitive primary system is a simply supported beam, obtained by elimination of internal supports and elimination the constraint developing bending moment in the first fixed support. The most effective primary system for continuous beam is proposed by Clapeyron. His primary statically determinate system is obtained by elimination of the constraints which prevent mutual rotation of two neighbouring sections over the supports. When all the moments of the supports are known, one may proceed with the determination of bending moments within the spans, the shear forces and reactions developed at each support. These computations will be carried out assuming that each span is a simply supported beam and it acted upon both by the applied loads and the moments of the supports just determined.
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APPARATUS
This apparatus are the main tools that had been used when doing this experiment ;-
NAME OF APPARATUS
A support frame
3 Nos. reaction support pier
2 Nos. load hangers
Beam specimen
A meter rule
A set of weight
PICTURE
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SAFETY PRECAUTION
All this had been applied when carry out this experiment ;-
1) Wearing a safety outfit when entering lab like wearing a lab outfit and safety 2) 3) 4) 5) 6)
boots. Follow all the lab rules. Do not play when doing an experiment. Follow the procedure of experiment. Repeat the procedures to avoid error. Read the meter two to three times to avoid error.
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PROCEDURES
1) The unit been warmed up by switched on the display unit. 2) By using the plate and bolt supplied with the apparatus and at predetermine distance between the support, reaction piers was clamped to the support frame. 3) Beam specimen was placed between the two cylindrical pieces of each support. Two screw at the top of each support been tightened by using fingers. 4) Load hanger was fixed to the position where the beam is to be loaded. 5) Display unit by connected the load cell from the support pier, each load call occupying one terminal on the display. 6) Recorded the initial reading for each channel was started with channel one. 7) Placed a suitable load on the load hanger and the reading was noted for each load cell. This represents the reaction at each pier. 8) Load on the load hanger was increased at suitable increments and for anch increment the pier reaction been recorded.
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RESULT (Theory Method)
Left – Hand span of beam, LL
= 500 mm
Right – Hand span of the beam, LR
= 1000 mm
Distance of load from left – hand support, X L
= 250 mm
Distance of load from right – hand support, X R
= 750 mm
Load On LL
Load On LR
Support Reaction
Left
Middle
Right
N
N
N
N
N
1
2
0.2
-15
17.3
2
2
0.7
-14.3
12.3
2
3
0.5
-13.6
17.7
3
3
1.0
-12.9
17.6
3
5
0.7
-11.5
18.4
5
5
1.6
-10.1
18.2
RESULT (By Using the Formula) 6 | Page
Left – Hand span of beam, LL
= 500 mm
Right – Hand span of the beam, LR
= 1000 mm
Distance of load from left – hand support, X L
= 250 mm
Distance of load from right – hand support, X R
= 750 mm
Load On LL
Load On LR
Support Reaction
Left
Middle
Right
N
N
N
N
N
1
2
0.6
2.1
0.6
2
2
0.8
2.75
0.8
2
3
1.0
3.4
1.0
3
3
1.3
4.1
1.3
3
5
1.7
5.5
1.7
5
5
2.1
6.9
2.1
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A) Position and Direction of load for the beam.
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B) Reaction at the Support.
Types of support.
Pin Support -- Support that have 2 reactions from left or right and from up or down. -- Example :- Ray and Rax.
Fix Support -- Support that have 3 reactions. -- 1 from right or left. -- 1 from up or down. -- 1 is the moment. -- Example :- Ray , Rax and Ma.
Roller Support -- Support that have just one direction that is from up or down. -- Example :- Ray.
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C) Graph of Reaction Against Load
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SAMPLE OF CALCULATION
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DISCUSSION
From this experiment, what would need to be discussed is an error that was appeared to the meter that detects load reading. There is a zero error on support of left – hand, - 8.5 N errors on middle- hand and 18.3 N errors on right – hand. This error must cause of mechanical problem of that equipment itself. Next, there is also a bit different between the readings were read by the device and the reading that was obtain by using a formula. This thing might happen because of an error that was obtained before or mistakenly of calculation using a formula. Lastly, even know there is a big different of result between the theoretical and experiment, but the equipment still can be use because of there is just a slight different of deflection between this both method. It was 0.7 deflections on theoretical and 0.68 on experiment.
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CONCLUSION
As the conclusion, the objective to determine the reaction of a two-span continuous beam was successfully achieved. Not just that, now all of us understand about continuous beam more that before. 1) If the material of the beam is changed from steel to aluminium, how does this affect the support reaction? Give reasons for your answer. - If the beam material changed from aluminium to steel, beams will become stronger as aluminium beams usually used for structural applications. Aluminium 6061-T6 has above average corrosion resistance, mach inability, and excellent for welding. This application is great for reducing the cost of damage to the beams of the building. 2) If a thinner beam is used, how does this affect the support reaction? Give reasons for your answer. - If a thin beam is used, the effect of an adverse reaction will occur on the support. This will cause the beam to become brittle and will be easily collapsed the building. This will require the high cost of repairing the collapsed beams. Otherwise it will endanger the lives of users if the building is built is not safe to use. 3) How does the experimental reactions compare with the theoretical. EXPERIMENT - The value is a bit lower than the value that was got using the formula. - The value of M for experiment is 0.68.
THEORETICAL - The value is a bit higher than the value that was get from the experiment. - Value of M for theoretical is 0.70.
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4) State the possible factors that might have influenced your results and possible means of overcoming it. - The reason that influenced the result might be because of the error that already there at the apparatus or might be because of the load that been use is little too old and had loss it weight. - This thing can be avoid by using the apparatus that had been maintained or been set the value to 0. The load also need to be replace to the new one.
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APPENDIX
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