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Which Bridge Design is Stronger?


Researched by Erik J 



The purpose of this experiment was to see which type of bridge is the strongest out of three types of bridges.

I became interested in this idea when I realized the increasing amount of traffic adds more weight on the bridges thus making them more likely to break.

The information gained from this experiment will help civil engineers to create stronger bridges for the increasing population. 



My hypothesis is that the Truss Bridge will support the most weight.

I base my hypothesis on the information I learned that tells me that truss and arch are two of the strongest types of bridges.



The constants in this study were:

v The weights  
v The micrometer  
v The Popsicle  sticks used to build bridges 

The manipulated variable was the type of bridge.

The responding variable was the flex the bridge undergoes

To measure the responding variable I will use a micrometer. 


1.Construct a stand for the bridges using Lego’s.

2.Construct a spanning bridge, made of Popsicle sticks, half a meter long using hot glue to fasten. (Looks somewhat like a railroad track up side down)

3.Construct a truss bridge, it looks like triangles between the two platforms, the platform is underneath the triangles.

4.Construct an arch bridge, looks like a platform with an arch above it

 5.Place a.45kg-4.50kg (10 weights) weight on the span bridge.

6.Measure the amount it flexes using a micrometer.

7.Record data.

8.Switch bridges to the truss bridge

9.Pace weights on new bridge 

10.Measure flex using a micrometer.

11.Record data

12.Place weights on the arch bridge

13.Measure the flex using a micrometer 

14.Record data

15.put data into graph


1 Box of 180mm Popsicle sticks 
3 Bridges constructed of Popsicle sticks
1 Stand constructed of Legos
2 45kg weights
2 .225kg weights
1 1.25kg weight



The original purpose of this experiment was to see which bridge would flex the most under load.

The results of the experiment were the truss bridge was the strongest and the arch was second. Span was weakest and flexed the least. 



My hypothesis was that the truss bridge would flex the least because of its known strength

The results indicate that this hypothesis should be accepted the truss bridge I built flexed the least.

Because of the results of this experiment, I wonder if bridges using cables would hold more than no cable bridges.

If I were to conduct this project again I would use other types of bridges so I could test all the types of bridges and maybe create a bridge to test. 



This report is about the effect of weight on bridges. We know they are going to flex but how much is the question. In this report I will give the reader the knowledge needed to perform the experiment. The types of bridges the experiment will use and a little knowledge about them.


           Truss Bridges are one of the types. Trusses have been built for many years in all places because they are very cheap to make. Their cost and strength are great factors that make truss bridges one of the most used bridges today. Truss bridges are used to cover long distances because of their strength. The triangle patterns push together and strengthen the bridge.


Span Bridges are next. Span bridges are an ok bridge only used for short distances like on freeway passes. Span bridges are weak because of poor support it’s like standing on a flat ruler. The span bridge works by brute force, all it does is take the weight and do the best it can with the weight it is given 
Arch Bridges are a very good type of bridges going back to when monasteries where still around. Arch bridges are used in canyons, reviens, and any large gap with sturdy walls. What it does is as the moor weight is on it the more it pushes on the sides of the canyon walls.


The people that design the bridges have to be very good in math and physics. The bridge design mostly depends on the type the engineers want the bridge needs to be. Most bridges today are mostly crosses between two kinds of bride.


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