Name___________________________________                                         Class_______



Bridge Construction Lab



In this lab you will be designing and constructing a bridge out of coffee stirrers and Elmerís glue. You will consider different bridge designs and incorporate these into your own structure. Your bridge will then be tested to find out its maximum load. The bridge will be weighed and a weight/load or optimization for the bridge will be calculated.



Materials (bridge)                                         


Coffee stirrers                                                              

Elmerís glue

Student bridge blueprint worksheet





Styrofoam board

Scale (measure in grams)




1. Using the Bridge Blueprint and using a ruler, draw how you want your support beams to look on your bridge. See the examples below:


2. You will need to make 2 Bridge Blueprints that are the same, one for each side of the bridge.


3. Have your design approved and then begin gather your building materials. You will need the coffee stirrers, Elmerís glue, push pins, scissors, and Styrofoam board.


4. To construct the bridge, pin your Bridge Blueprint to the Styrofoam board.


5. Take the first coffee stirrer and lay it on one of your lines, so only the edge is touching the paper (DO NOT LAY IT DOWN FLAT). Hold it in place with a few push-pins.


6. Then pick up the next coffee stirrer and place it with the small edge touching the paper right next to the first coffee stirrer. Put a dot of glue to connect the two edges of the sticks together. Donít overlap them.


7. Continue doing this, marking and cutting the coffee stirrers when you need to cut the stick shorter with scissors.


8. Once you have completed laying and gluing all the coffee stirrers, so that all the lines are covered, repeat this with the second Bridge Blueprint. (NOTE: YOU ARE GLUING THE COFFEE STIRRERS TO EACHOTHER, AND NOT TO THE PAPER.)


9. Wait a full day, and then pull the bridges off the Styrofoam and the paper. Finally cut 2 coffee stirrers in half and use these 4 pieces to connect the bridge sides to each other. Put a dot of Elmerís glue and a closepin to hold the bridge together as it dries.


10. The next day, it will be time to test the bridge load.


11. Weigh the bridge and record the mass in grams.


12. Place one textbook at a time on top of the bridge and when it breaks, record this number.




Amount of textbooks at breaking point_______________________


Weight of bridge in grams (g) ______________________________




   Number of textbooks    .          =        _________________________

    Weight of bridge


The above number is your optimization number.




1. Why do we use the optimization number in figuring out whose bridge was the best? Why not just use how much load it could hold?






2. What changes would you have made to your bridge design to make it hold more load? Would you even change your design?