I’ve been searching high and low for an earthquake engineering design challenge that gave students more control in planning and evaluating their earthquake-resistant constructions than the common “toothpicks and marshmallows” challenge often seen in primary and middle grades. So I was thrilled when I finally stumbled upon a string of videos from the Incorporated Research Institutions for Seismology or IRIS titled “Build a Better Wall” featuring a hinged craft stick structure that would do just that.
While IRIS construction called for bolts and screws, I found brass fasteners to be effective replacements that dramatically cut the projected cost for a class set and got to work! With 5 working shake structures able to be produced from a single 2×4 we were ready to go!
Day 1: Introducing the Challenge
Because we were piloting this lesson for the first time, students were plunged into the earthquake setting head on. We watched the opening minutes of a YouTube film on the 1989 San Francisco Quake, where students were prompted to watch closely the behavior of the hanging lights and glassware in the opening scenes. These objects oscillate back and forth, which students were able to associate with waves despite no prior lessons on waves and communication (as intended in future years!) From here I gave them a brief introduction of quake waves, demonstrating the compressional wave behavior of P-waves and then “side-to-side” S-wave motion with the help of a slinky and a piece of string tied to the center, showing how the matter did not advance forward or backward, but rather returned to its original location after the wave energy had passed.
Using the presentation above and linked to here students were introduced to substructures, a grade 3-5 “Structure and Function” Crosscutting Concept NGSS element, drawing comparisons to the substructures of different parts explored in their life science unit completed prior to. Students were introduced to three substructures commonly used in buildings, shear walls, cross members or beams, and gussets. Students were also informed that a structurally resistant building might not be enough, land developers are also looking for affordable and low-weight designs too!
Day 2: Planning and Building our Structures
Day 2 was a full day of student driven work. Students worked together to plan their structures while I worked the room with classroom teacher, Holly Weinberg probing students for the thinking behind their designs. With the pieces cut out of basic copy paper and attached with alligator clips materials were cheap! Limited time led to construction being pushed into the beginning of the third day. Before moving on to the construction part, students had to calculate the cost and additional weight of their substructures to their wall.
Day 3: Testing and Evaluating our Structures
Test day! Despite tight time I introduced the wave thinking once again in an effort to help students develop a “repeatable, fair test” when evaluating all of their structures. With the help of a free metronome app students practiced creating a consistent motion pattern with their hands before being charged with delivering 8 long wavelength and 8 short wavelength seismic vibrations to their prototypes. Before structures were tested, students entered their cost and weight data on to a class table. Would the lightest, cheapest structures hold up to the test?! When the results came only 3 of the 5 structures met consensus that they had survived the quake. Of those three 2 “bids” came in strikingly close with the 3rd effective, but costly and heavy.
Day 4: Reflecting and Redesigning
While unable to help on the final day, Mrs. Weinberg held down the ship and had top teams share their successes and teams with structural failures “lessons learned”. In the future I plan to have students complete this challenge after exploring the patterns of locations where earthquakes occur (to tie in with their “West Region” Social Studies Exploration) and perform some sort of “Earthquake Program” that would introduce the different wave formations and some of the more curious challenges to quake-resistant structures such as harmonic resonance and foundation liquefaction that I would not expect 4th graders to actively investigate and prepare for. I might also introduce the challenge across all the classes at once in this way to save time for the classroom teacher to focus on the planning stages exclusively in the first day.
Thanks to Holly Weinberg for allowing me to pilot this investigation with her students and to IRIS for sharing their resources publicly for all! More detailed lessons, the presentation, and student notebook can be found by following many of the links above and will also be available in an organized way by the beginning of September 2017 on the Science Center fourth grade curriculum website.