Science Fair Final 56703h

The Effect of Bridge Design on Weight Bearing Capacity

Ani Guda 16 November 2014 C Block

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Abstract The purpose of the experiment to find out strength of bridge for various design of bridges. In this experiment, three different designs, an arch, truss and plank shapes are tested for its strength. The strength of the bridge is determined by calculating weight bearing capacity. The higher the weight bearing

capacity, the stronger will be the bridge. The hypothesis is, if the type or the design of the bridge is related to the maximum amount of weight the bridge, then the truss bridge will have the highest weight bearing capacity because the truss bridge is built with that are inclined. The incline will have the ability to spread the weight across the bridge. The bridges are built using Popsicle sticks and wood glue to make the shapes of the bridges. The weight of each bridge is calculated before starting the experiment. The bridges are ed on each end on a side table.

Weights are added on to the bridge until the bridge breaks. The weight bearing

capacity is calculated using the ratio of total weight added to each bridge until the breaking point divided by the weight of the bridge. The experiment showed that a truss bridge is the strongest of all. The results match with the hypothesis that truss bridge is able to effectively distribute the weight with compression and tension in inclined . The results can be applied in the real world when deg bridges. The engineers can determine the shape of bridge based on the expected traffic flow.

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Table of Contents Abstract…………………………………………………………………………………………… Purpose…………………………………………………………………………………………….1 Research…………………………………………………………………………………………...2 Hypothesis………………………………………………………………………………………....2 Materials…………………………………………………………………………………………..2 Procedure…………………………………………………………………………………….........3 Observations………………………………………………………………………………………4 Conclusion………………………………………………………………………………………...4 Recommendations………………………………………………………………………………....4 Applications……………………………………………………………………………………….5 Bibliography………………………………………………………………………………………5 Acknowledgements……………………………………………………………………………….5 Appendix………………………………………………………………………………………….6

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Purpose The purpose of this experiment is to measure the strength of the bridge for various bridge designs. Three different types of bridges such as Truss, Arch, and Plank are tested for different loads until it breaks. The weight bearing capacity is the strength to weight ratio that are measured to determine the strongest bridge design. Research There are many different types of bridges around the world. The type of bridge to build at a given location depends on many factors such as, the type of traffic and the maximum weight that will cross the bridge, the locations that are available for foundations for the bridge. The weight on the bridge structures can cause failure therefore, the design and shape of bridge is an important study. The research will cover the study of different models and investigate which type of bridge has the greatest strength. The most basic bridge design is a plank bridge. But sometimes, plank bridges cannot span great distances. The truss bridges are triangular which are made up of straight beams and inclined beams. The other type is an Arch truss bridge is curved in shape and combines elements of truss. The truss and arch bridges are able to carry big weights and also span great distances. In this project, plank, truss and arch bridges of different shapes are built and their strengths are measured. The bridges are built using Popsicle sticks. These bridges will be tested by adding weights and measure the strength to weight ratio as this is an important measure. While doing the experiment, the maximum amount of weight, each bridge can hold will be measured. After measuring the weight, the strength to weight ratio of each bridge will be compared. The strongest bridge will be the higher weight that the bridge can hold without 1

breaking. The study of these factors will help engineers to choose and construct a particular type of bridge at a given location. Hypothesis If the type or the design of the bridge is related to the maximum amount of weight the bridge can hold, then the truss bridge will have the highest weight bearing capacity because the truss bridge is built with that are inclined. The incline will have the ability to spread the weight across the bridge. Materials 

Popsicle wood sticks

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Wood glue

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Small piece of rope

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Stapler

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Two side tables

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Bricks (weighing at 2 pounds)

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Spring Balance

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Ruler

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Journal.

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Procedure 1. Gather all the materials that are needed for the experiment. 2. Draw the shapes of arch and truss bridge. Begin building a truss bridge using Popsicle sticks by gluing the sticks at their ts. Build an arch bridge in the same manner as truss bridge by gluing the ts. 3. Once the bridges are ready, weigh them before starting the experiment. 4. The experiment uses bricks as loads that will be added to the structure to measure the strength. Weigh the bricks and note them in the journal. 5. Place two side tables apart and place the bridge with their edges ed on each side on the side tables. 6. Start adding bricks on the bridge until it breaks. 7. Record how many bricks it took for a single bridge to break. 8. Do the same for the next two bridges. 9. Once the measurements are made, then calculate the weight bearing capacity using the ratio of total weight added to the bridge until breaking point divided by the weight of the bridge.

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Observations The experiment showed that truss bridge was able to hold most of the weights and this was strongest compared to arch and plank bridges. The weight bearing capacity or the strength to weight ratio is highest at 145.45 for a Truss, 41.38 for Arch and 111.11 for Plank Bridge. The next strongest bridge after Truss bridge was the Plank Bridge and weakest bridge was an Arch Bridge. The results of the experiment matches with hypothesis that Truss Bridge is the strongest.

Conclusion The experiment proved that the truss bridge was able to hold more weight and stronger to other type of bridges. The results match with the hypothesis. The incline of truss bridge were able to effectively distribute the weight due to compression and tension until it reaches the breaking point, whereas the arch and plank bridges buckled and broke as the weight was being added gradually. The experiment showed that truss bridge is strongest followed by arch and then plank design of bridges.

Recommendations This experiment could have been better by using stronger wood than a Popsicle sticks. It is also recommended to add additional shapes of bridges.

More number of trails are

recommended to maintain the accuracy and repeatability of the results. It was noted that staking

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bricks was difficult to fit into the structure, instead a bucket could be hanged in the middle of the bridge to add weights gradually placed until it breaks. Applications In real world, bridges are needed to cross railroad tracks, rivers and highways. They are an important part of the transportation infrastructure. The traffic will determine the type of bridge to be built in a particular area. If there is a lot of traffic, based on this experiment, a truss bridge is recommended. Bibliography "The Effect of Bridge Design on Weight Bearing Capacity." The Effect of Bridge Design on Weight Bearing Capacity. Web. 23 Nov. 2014. . Cabrera, Sonny. "Cosmos - Students." Cosmos - Students. Web. 23 Nov. 2014. . VanCleave, Janice Pratt. Janice VanCleave's Great Science Project Ideas from Real Kids. Hoboken, NJ: John Wiley & Sons, 2007. 99. Print. Acknowledgments

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The student would like to thank his parents for helping in buying materials and helping me in conducting the experiment. The student also likes to thank his teacher for guiding him throughout the science fair project for her coaching and correcting the work.

Appendix Data table: Table 1: Data showing the weight bearing capacity for various design of bridges

Bridge Type Arch Truss Beam

Weight of Bridge (gms) 131.54 99.79 40.82

Weight at breaking (gms) 5443 14515 4535

Strength to Weight Ratio = Weight at breaking/Weight of Bridge 41.38 145.45 111.11

Graph:

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16000

Weight bearing capacity for different types of bridges 14515

14000 12000

Arch

Truss

Beam

10000 8000 5443

6000

4535

4000 2000 131.54

0

99.79

40.82

Weight of Bridge (gms)

41.38

Weight at breaking (gms)

145.45

111.11

Strength to Weight Ratio = Weight at breaking/Weight of Bridge

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