Testing
The bridge was tested to see if it met the following requirements that were defined in the introduction:
2. Midpoint of road deck must be 140mm above horizontal resting position when articulated.
​6. 10 gram mass on articulation component allowing gap for printer paper to slide under bridge
7. Supports load between 18.9 to 20 kg.
8. Weight of bridge must be 85 grams or less (with articulation hard components removed)
9. Max vertical deflection of 25 mm
10. Articulation from fully closed to fully open must be done in under 60 seconds.
​
An articulation test was conducted to measure requirements 2 and 10. The bridge was timed while it articulated open, and once the bridge was open, the height of the midpoint of the road deck was measured. A tensile test on the string was used to measure requirement 6. A 10 gram mass was hung from the string and standard printer paper was used to determine if the bridge lifted. The loading test determined requirements 7 and 9. An Instron was used to measure the force and deflection the bridge withstood. An additional weight test was used to determine requirement 8.
​
One issue occurred during the tensile test. Initially, a slotted weight with hanger was planned to be hung from the articulation cord. However, a few days before testing the project mentors confirmed that there were no weights with hangers in the building. To resolve this, popsicle sticks were placed in a Ziplock bag and hung from the articulation cord using a paper clip. The makeshift weight was weighted using a scale, and the mass could be adjusted by adding or removing popsicle sticks. The makeshift weight allowed for the mass to be low enough to test for the requirement of 10 grams.
​
​
Articulation Test
Two values were tested during the articulation test: the time it takes to raise the bridge and the maximum height of the midpoint of the road deck. A video was taken of the bridge articulating open the start and end times of the articulation was used to determine the articulation time. Once articulated open, the road deck midpoint height was measured using a tape measure. The bridge articulated open with an average of speed of 0.97 seconds, and the midpoint reached an average height of 155.3 mm.
Image 4.1: Articulation Test Data Sheet
Video 4.2: Articulation Test Footage
Tensile Test
The tensile test determined what weight would cause the bridge to lift when applied to the articulation string. A mass was hung from the bridge, and 1 gram was added to the weight until a sheet of printer paper was able to slide under the bridge. The bridge lifted when 16 grams was applied to the articulation cord.
Image 4.3: Tensile Test Data Sheet
Image 4.4: Mass Hung onto Cord
Video 4.5: Tensile Test Footage
Load Test
The load test determined the load the bridge could withstand the required load and its displacement under that load. The bridge was placed on the abutment and tested in the Instron. The bridge withstood a force of 190.02 N (19.4 kg) and displaced 1.66 mm under that load
Image 4.6: Bridge in Instron
Image 4.7: Force vs Displacement Graph
Weight Test
The weight test determined the total mass of the bridge and articulation tower. The bridge and articulation tower were placed on a scale and the total mass was 79.5 grams.
Image 4.8: Mass of Bridge + Tower