Report

Name: Haocheng Yang (Hochan)

CEG No:08036409

AbstractBridges give the impression of being rather simple structural system. Indeed, they have always occupied a special place in the affections of structural designers because their structural form tends to be a simple expression of their functional requirement (John & Sons,1996 ). Bridges give the impression of being rather simple structural system. Indeed, they have always occupied a

special place in the affections of structural designers because their structural form tends to be a simple expression of their functional requirement (John & Sons,1996 ).

ContentsAbstract………………………………………………………………………………………2Questions……………………………………………………………………………………4Variables………………………………………………………………………………………4Hypothesis……………………………………………………………………………………4Background…………………………………………………………………………………5Material List…………………………………………………………………………………6Experimental procedure1. Design two simple

2

bridges……………………………………………………92. Build the

bridge……………………………………………………………………9

3. Process of Tests……………………………………………………………………14

4. Experimental Result……………………………………………………………15

Data analysis and discussion1. Daya

analysis………………………………………………………………………17

2. Discussion……………………………………………………………………………18

Conclusion…………………………………………………………………………………20Ideas for future research……………………………………………………………21Acknowledgments……………………………………………………………………22Bibliography………………………………………………………………………………23

3

Questions How do the cables and towers carry the load that is on the bridge? Can a suspension bridge carry a greater load than a simple beam bridge?

Variables The number of coins (weight) Different materials cables Different bridge (beam bridge or suspension bridge)

Hypothesis The suspension bridge will be able to support more amount of weight than the beam bridge.

4

BackgroundA bridge is a large structure that is used to overcome obstacles. It is precisely used to cross traffic routes (such as roads, railways, waterways, etc.) or other facilities (such as pipelines, cables, etc.) across natural barriers (such as rivers, straits, canyons, etc.) or artificial barriers (freeways, railway lines). The structure. Girder bridges are mainly girder-bending main bridges. The main beams can be solid web beams or truss girders (open web beams). The real belly beam has a simple shape and is convenient for production, installation and maintenance. It is widely used in bridges with medium and small spans. Real belly beams are not economical to use. Suspension bridges are bridges that act as major load-bearing components with cables or chain cables that absorb tension. Suspension bridges consist of suspension cables, pylons, anchors, booms, and bridge decks. Suspension cables are the main load-bearing components of suspension bridges. They are mainly subjected to tensile forces and are generally made of steel materials (steel wires, steel strands, steel cables, etc.) with high tensile strength. Because the suspension bridge can fully utilize the strength of the 5

material, and has the characteristics of material saving and light weight, the suspension bridge has the largest spanning ability in various system bridges, and the span can reach 1900 meters or more. The main disadvantage of a suspension bridge is its small stiffness, which tends to cause large deflections and vibrations under load, and it is important to take appropriate measures. The Golden Gate Bridge is one of the best examples. It is the world's first suspension bridge with a span of over a kilometer.

Material ListBox of drinking straws

Masking tape

6

Thread and Iron wire

Scissors

Disposable plastic cup7

Many coins (Pennies)

Metric ruler

8

Paper clip

Experimental procedureIn order to complete this experiment, we collected materials (see Materials List) at first. And the experimental procedure is as follows in four parts.1.Design two simple bridgesAccording to the experimental content, we design two simple beam bridge and simple suspension bridge 9

respectively. And then draw the sketch, as shown in

Figure 1 and Figure 2：

Figure1. Design of beam bridge Figure 2. Design of suspension bridge

2.Build the bridgea) Build the simple beam bridge

- Because our straws are the type of bendable, so cut the part of flexible as the first step. Cut a total of twenty straws (each 13 centimetres long) in this way and make sure they all the same length, as shown in Figure 3.

Figure 3.- Then cut two short pieces of straw, each 3

centimetres (cm) long, as shown in Figure 4.

10

Figure 4.

- Take a three centimetres piece of straw and place it between two straws we prepared in the first step, then tape the bottom three straws together and the top two straws together, as shown in Figure 5. And this is the tower for the bridge.

Figure 5.

- Tape one tower to the edge of a deck, table or chair. The short straw piece should be at the bottom of the tower (and the pointy end without a short piece should be at the top). Tape the second tower to the second piece of furniture at the same height. Keep the distance of two towers is 13cm.

- Use the 13 centimetres long straw which we prepared in the first step as the deck of the bridge. And place it between the towers so its ends rest on the short pieces, as shown in Figure 6. Now finished

11

to build a simple beam bridge.

Figure 6.b)Build the simple suspension bridge

- Repeat process I mentioned above to build a new beam bridge.

- In order to change the beam bridge into the suspension bridge. Use a needle to pierce the centre of the straw which between two towers. Prepare the middle of a 100 cm piece of thread (acting as our bridge cable), threaded it through the middle hole on the new bridge deck straw and tie it around the middle of the straw, as shown in Figure 7. Place the straw between the towers. Pass each end of the cable over a tower and down the other side.

12

Figure 7.- To fix the suspension bridge, surround each end of

the cable with a paper clip. Slide the paperclip away from the tower until the cable is tightened. The clip is then fixedly secured to the furniture, as shown in Figure 8. Overall, we finished all the steps to build the simple suspension bridge, as shown in Figure 9.

13

Figure 8.

Figure 9.14

3.Process of Tests- Use a disposable plastic cup as load tester and use

the different value of coins (penny) as weights to test the bearing capacity of two simple bridges.

- Hang the cup on the middle of the bridge deck straw, and gradually put the coin into the tester

cup。- Record the number as well as the value of pennies

the paper cup can hold before the bridge fails as the data and then use the experimental data and the data of table 1 to calculate the mass and write it in the data table. Furthermore, record how does the bridge fail.

- The experience for each design of bridge will be repeated six times. Every test we will replace a new bridge deck straw.

Value of Coin WeightTwo Pound Coin 12.0gOne Pound Coin 9.5gFifty Pence Coin 8.0g

Twenty Pence Coin 5.0gTen Pence Coin 6.5gFive Pence Coin 3.25gTwo Pence Coin 7.12gOne Penny Coin 3.56g

Table 1 The weight of different value of coin

15

4.Experimental ResultResults obtained are summarized in table 2.Bridge Design

Trial Value and Number of Coins

Mass Average Mass

How does the bridge fail

Beam Bridge

1 50Px1010Px27

255.5g 251.83g Bridge deck straw broken

2 50Px1010Px26

249g Bridge deck straw broken

3 50Px1010Px251Px2

251.62g Bridge deck straw broken

4 50Px1010Px255Px2

249g Bridge deck straw broken

5 50Px10 242.5g Bridge

16

10Px25 deck straw broken

6 50Px1010Px255Px11Px5

263.55g Bridge deck straw broken

7 50Px1010Px551Px2

251.62g Bridge deck straw broken

8 50Px3310Px47

569.5g 523.3g Bridge cable broken

9 50Px3310Px10

329g Bridge deck straw broken

10 50Px3310Px48

576g Bridge cable broken

11 50Px3310Px15

361.5g Bridge deck straw broken

12 50Px3310Px47

569.5g Bridge cable broken

13 50Px3310Px4720Px33

734.5g Bridge tower broken

17

Table 2 The data of Beam Bridge and Suspension Bridge

Data analysis and discussion.1.Data analysisThe following results have been obtained through the experiment. When the beam bridge (only bridge deck, no cable supports) was tested, the cup of pennies average weighed 251.83 grams. When the beam bridge failed, this was likely because the deck straw bent downward as more coins were added until it bent so much that it slipped down between the two towers. When the suspension bridge (bridge with cable supports) was tested, the cup of pennies average weighed 523.3 grams. When adding coins in the cup, the cable (thread) was under tension and

18

reinforced the bridge deck straw, pulling it upward (while compressing the towers) and allowing the bridge to hold more coins. When the coin is continuously added to the cup, the bridge deck straw bent downward and at the same time the cable (thread) are stretched (bear greater tension). So, when the suspension bridge eventually failed, we met a total of three cases: >Because the cable (thread) cannot afford too much tension and finally break, as shown in Figure 10. (meet in table 2 trial 8, trial 10 and trial 12)>The bridge deck straw likely similarly bent into a V-shape (the deck straw broke), but because it was attached by the cable the straw couldn't fall and instead the cup may have slipped off of the straw, as shown in Figure 11. (meet in table 2 trial 9 and trial 11) >Too much compressive force causes tower to bend and finally break, as shown in Figure 12. (meet in table 2 trial 13)

Figure 10.

19

Figure 11.

Figure 12.In this activity, the suspension bridge was able to hold more than two times weight than the beam bridge.

2.Discussiona) Problem

- A 1 pound or 2 pound coin has a relatively large weight, so a 50 pence coin is used as a weight to test the performance of the girder bridge and the suspension bridge, which will result in a large experimental error.

- Thread is the only material used as the cable in the 20

previous test. However, the effect of tension on the elastic deformation of thread is too large which caused the thread could not support too much tension or the bridge deck straw likely similarly bent into a V-shape (broken) due to the thread’s elastic deformation.

b) Solution- We choose more small-weight coins such as ten

pence(6.5g), five pence(3.25g) and one penny(3.65g) as weights. Thus, we can get more accurate data and reduced experimental error.

- In addition to use the thread as the cable, try to use an iron wire as the cable which with a less elastic deformation and stronger. After that, the larger weight can be support by the suspension bridge. (meet in table 2 trial 13)

Conclusion21

According to this experiment, we can know the different supporting principles of two different bridges (suspension bridge, beam bridge). Different materials can also lead to different experimental results. Suspension bridges can support double or more weight bridges. In addition, each part of the bridge will affect its carrying capacity. Therefore, every detail is important when designing and building bridges.

22

Ideas for future research

In this project, we only compared the bearing capacity of simple girder bridges and simple suspension bridges. In the future, more in-depth experiments can be conducted on the basis of this project:> Test the effect of different spans on the bearing capacity of the bridge by changing the length of the pipette.>Change the cable length and test the effect of the cable length on the load carrying capacity of the suspension bridge.> Change the influence of different fixed positions of cables on the bearing capacity of suspension bridges.> Change the height of the tower and test the effect of tower height on the bearing capacity of the suspension bridge.> Finally, summarize all experimental data and calculate the best parameters for each part of the bridge to achieve the best performance of the suspension bridge.

23

Acknowledgments

The experiment was completed with the meticulous guidance and strong support of Daniel Ado. At the same time, I learned a lot about bridges and physics in the course of this experiment, and my experimental skills have greatly improved.In addition, I would also like to thank the team members for their great support for this experiment and for the writing guidance for the report. The team members have made great efforts to successfully complete the experiment.Finally, I would like to express my heartfelt thanks again to the teachers and classmates who care and help me.

24

Bibliography

Wiley, J & Sons. 1996. Seismic Design and Retrofit of Bridges. P686.

En.wikipedia.org.（2018）. Beam bridge. <online> Available at: https://en.wikipedia.org/wiki/Beam_bridge <Accessed 5 Mar.2018>.

En.wikipedia.org.（2018）. Suspension bridge. <online> Available at: https://en.wikipedia.org/wiki/Suspension_bridge<Accessed 5 Mar.2018>.

ENCYCLOP®DIABRITANNICA.(2018). Suspension bridge. <online> Available at: https://www.britannica.com/technology/suspension-bridge<Accessed 7 Mar.2018>.

25

History of Bridges.(2018). Suspension Bridge - From Earliest to Modern Designs. <online> Available at: http://www.historyofbridges.com/facts-about-bridges/suspension-bridges/<Accessed 7 Mar.2018>.

History of Bridges.(2018). Beam Bridge Facts, History and Design. <online> Available at: http://www.historyofbridges.com/facts-about-bridges/beam-bridge/<Accessed 7 Mar.2018>.

26