PASCO ME-6992B Advanced Structures Set - Manual (Page 13)

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M o d e l N o . M E - 6 9 9 2 B M e a s u r i n g B r i d g e D e f l e c t i o n U n d e r L o a d
9 012-12719B
Measuring Bridge Deflection Under Load
Because the members are made of plastic, it is easy to show bending in a bridge
using relatively small loads.
Using a Motion Sensor
In Figure 22, the bridge is loaded by hanging a weight (Large Slotted Mass Set, PASCO Model ME-7566) from
the center of the bridge. A Motion Sensor (PS-2103) is placed on the floor and pointed up toward the bottom of
the weight hanger. A PASPORT interface (in this case, the Xplorer GLX, PS-2002) is used to record the amount
of mass and the distance to the bottom of the weight hanger. A graph of the deflection as a function of the load is
shown next to Figure 22.
Hint: For the GLX, set the Motion Sensor sample rate to 50 Hz. In the Sensor Setup window, change the
‘Reduce/Smooth Averaging’ from ‘Off’ to ‘5 points’.
Using Load Cells
Figure 23 shows two bridges of the same type but different scale. For a given load the deflection is different.
Also note that the forces in some of the members are being measured using load cells to discover the difference
caused by the size of the bridge.
Bridge Challenges for Students
Perhaps the best way for students to learn about bridges is to give them a task to accomplish with limited
resources by any means possible. Here are two suggestions to challenge your students.
NOTE: Do not attempt to
load the bridge to the
point of breaking.
Figure 22: (Left) Deflection of bridge under load.
(Above) Displacement vs. Mass plotted using
PASCO’s DataStudio software.
Figure 23: (Above) Same load for different scale bridges. (Right) Displacement vs. Mass