Education Track

🏗️

Structural Engineering

Education Track · 5 Build Challenges · Household Materials

Concepts covered in this track

1 Load & Structure

2 Material Properties

3 Joint Design

4 Triangulation & Geometry

5 System Optimization

Complete all 5 experiments to find out if chemistry is your path.

Ages 10+ · Free Resource · stemigoo.com

Free — household itemsChallenge 1 of 5

Paper Bridge Challenge

Engineering concept: Load & structure — why shape distributes force more efficiently than adding more material.

Track arc: Load vs. structure → material properties → joint design → triangulation → optimization

What You Need

2 sheets of paper
Tape (30cm strip)
Scissors
2 stacks of books (~15cm gap between them)
Coins or small washers for load testing

The Challenge

Span the gap using only the paper and tape. Build at least 3 different designs and load-test each one. Your goal is not just the strongest bridge — it's understanding why one design outperforms another.

Structural Techniques to Try

Flat sheet — baseline, no modification
Accordion fold — fold back and forth like a fan
I-beam — fold up both long edges to create flanges
Rolled tube — roll lengthwise into a cylinder

🔬 The Engineering

A flat sheet of paper has almost no resistance to bending — all the material is at the neutral axis where stress is lowest. Folding moves material away from the center, where bending stress is highest. An I-beam does this deliberately: the flanges carry bending load while the web resists shear. Real steel bridges use exactly this logic. More material in the wrong place helps nothing.

Full project: stemigoo.com/projects/paper-bridge-challenge

My Design Log

Before you build — predict: which design will hold the most?

Why?

Design	Sketch	Coins held	How it failed
Flat sheet
Accordion
I-beam
Rolled tube

Did your prediction match?

○ Yes○ No

What surprised you?

Which failure mode was most common?

○ Bending○ Buckling○ Tearing at supports

Key insight from this challenge

~$3 · 2 items to buyChallenge 2 of 5

Egg Drop Challenge

Engineering concept: Material properties — different materials fail differently, and choosing the right material is a design decision, not an afterthought.

Track arc: load vs. structure → Material properties → joint design → triangulation → optimization

What You Need

1 raw egg
10 plastic straws
30cm tape
Scissors
Optional: rubber bands, cotton balls, thin cardboard
A drop height of at least 1.5 meters (chair, table, or second floor)
A plastic bag or newspaper to catch the mess

The Challenge

Build a protective structure for the egg using only the given materials. Before you build, complete the prediction table. Drop from 1m, then 1.5m, then as high as you can manage.

Key Question to Answer

Does your structure work by being rigid (transferring force around the egg) or flexible (absorbing the impact energy)? Which approach is better — and why?

🔬 The Engineering

Impact force = mass × deceleration. To protect the egg, you need to slow its deceleration — spread the stopping force over a longer time and larger area. Rigid materials (hard plastic, cardboard) transfer force efficiently but concentrate it at contact points. Flexible materials (foam, rubber) deform on impact, extending the deceleration time and distributing force. Real crash structures (car bumpers, bike helmets) use both in layers.

Full project: stemigoo.com/projects/egg-drop-challenge

My Design Log

Sketch your design before building

My structure works by:

○ Being rigid○ Absorbing impact○ Both

Materials chosen and why:

Material	Why I chose it	Rigid or flexible?

Drop height	Predict: survive?	Result
1.0 m	○ Y ○ N	○ Survived ○ Cracked ○ Broken
1.5 m	○ Y ○ N	○ Survived ○ Cracked ○ Broken
m	○ Y ○ N	○ Survived ○ Cracked ○ Broken

Where did your structure fail first?

What would you change about your material choices?

~$4 · 3 items to buyChallenge 3 of 5

Straw Suspension Bridge

Engineering concept: Joint design — connection points are where structures fail, and how you attach members to each other is as important as what the members are made of.

Track arc: load vs. structure → material properties → Joint design → triangulation → optimization

What You Need

20 straws
60cm tape
String or thread (80cm)
Scissors
2 stacks of books (~20cm gap)
Coins for load testing
Small paper cup to hold the load

Suspension Bridge Basics

Your bridge needs: two towers (vertical straws), main cables (string from tower top to tower top, anchored behind), and hangers (short vertical strings from main cable down to deck). The joints where hangers meet cable and deck are your design variable.

Steps

Build two towers of equal height at the edges of your book stacks.
Run the main cable from one tower top, dipping down to mid-span, up to the other tower, then anchored behind each stack.
Attach a deck (flat straws) using hangers from the main cable.
Load-test. Note where it fails first — is it always at a joint?
Redesign one joint type and retest.

🔬 The Engineering

Suspension bridges carry load in tension (cable being pulled) rather than compression (beam being pushed). Tension members are far more efficient — cables can carry loads that would buckle a beam of the same weight. But every load transfer happens at a joint. If the hanger pulls out of the deck, the deck falls — not because the cable failed, but because the connection failed. Joint design is where bridge engineering lives.

Full project: stemigoo.com/projects/straw-suspension-bridge

My Design Log

Sketch your bridge design — label towers, cables, hangers, deck

Joint type	How attached	Did it hold?
Tower base		○ Y ○ N
Cable to tower top		○ Y ○ N
Hanger to cable		○ Y ○ N
Hanger to deck		○ Y ○ N

Which joint failed first?

How did you fix it?

Max load before failure

Name a real bridge that uses this same system

~$4 · 3 items to buyChallenge 4 of 5

Earthquake-Proof Tower

Engineering concept: Triangulation — triangles resist deformation under lateral force in a way no other shape does, and this single principle underlies most structural engineering.

Track arc: load vs. structure → material properties → joint design → Triangulation & geometry → optimization

What You Need

20 straws or toothpicks
Marshmallows or small clay balls (for joints)
Tape (backup for joints)
A ruler
A smooth surface to build on
A book to simulate earthquake lateral force (push the base)
A small weight for the top (coin or eraser)

Steps

Build a square-frame tower at least 30cm tall. Shake test: push the base sideways. What happens?
Add a single diagonal brace to one square panel. Test again.
Brace every panel. Test again. Measure the difference in sway.
Try building a tower using only triangles — no squares at all. Compare its height limit and stability.

🔬 The Engineering

A square frame has four joints — push one corner and the shape shears into a parallelogram. A triangle has three joints — there is no way to deform it without bending a member. This is why every truss bridge, Eiffel Tower, and geodesic dome is built from triangles. Seismic engineers add diagonal bracing to buildings specifically to triangulate what would otherwise be square frames. The diagonal doesn't add much material — it adds a geometric constraint that forces load into compression and tension rather than rotation.

Full project: stemigoo.com/projects/earthquake-proof-tower

My Build Log

Tower height:cmNumber of panels:

Configuration	Sway when pushed	Collapsed? Y/N
Square frames only
One brace added
All panels braced
Triangles only

Square under lateral force

Triangulated — same force

How many triangles in your final design?

Name one real-world structure that uses this principle

~$13 · 4 items to buyChallenge 5 of 5

Pulley System Crane

Engineering concept: System optimization — every design involves trade-offs, and engineering is the discipline of choosing the right trade-off for the specific constraint you're working under.

Track arc: load vs. structure → material properties → joint design → triangulation → System optimization

What You Need

2–3 small pulleys, curtain rings, or round pencils as axles
String or thin rope (2 meters)
A fixed support to attach to (door handle, towel rail, chair back)
A small weight to lift (book, bag of coins — know its weight)
A kitchen or postal scale (to measure pulling force)
Optional: a ruler to measure rope pulled vs. distance lifted

Steps

Single fixed pulley: Attach one pulley to your support. Run string over it. Lift the weight. Measure force needed. Record rope pulled to lift 10cm.
Moveable pulley: Attach a second pulley to the weight itself. Run string from fixed point → under moveable pulley → up and over fixed pulley → to your hand. Measure force. Record rope pulled.
Compound system: Add a third pulley. Repeat measurements.
For each configuration, calculate: force saved vs. extra rope needed.

🔬 The Engineering

A pulley system trades force for distance. Each additional moveable pulley roughly halves the force needed — but you must pull twice as much rope. Mechanical advantage = load ÷ effort. The "correct" pulley system depends entirely on your constraint: do you need to minimize force (heavy load, weak operator) or minimize rope travel (limited space)? There is no universally optimal system — only optimal for a specific set of requirements. This is the definition of engineering design.

Full project: stemigoo.com/projects/pulley-system-crane

My Measurements

Weight of load

System	Rope pulled to lift 10cm	Mechanical advantage
No pulley (direct lift)	10 cm	1
1 fixed pulley
Moveable pulley
3-pulley compound

The trade-off in one sentence: as pulleys increase, force ___ and rope needed ___.

Design a system for a specific job:

Scenario: you need to lift a 5kg load but can only pull with 1kg of force. How many pulleys minimum?

Trade-off you accept

Looking back at all 5 challenges — what single principle connects them all?

You finished the Structural Engineering Track.

Five challenges. Five real engineering principles. Here's where each one leads.

Load & Structure

Structural engineering, architecture, aerospace design

Material Properties

Materials science, product design, civil engineering

Joint Design

Bridge engineering, mechanical assembly, robotics

Triangulation

Seismic engineering, geodesic structures, truss design

System Optimization

Mechanical engineering, systems design, manufacturing — every engineering discipline ends here

Want to go deeper? Real resources.

PBS Design Squad — Free engineering design challenges for all ages.
pbslearningmedia.org/collection/design-squad

TeachEngineering — Free curriculum library from K–12 through university-level engineering concepts.
teachengineering.org

DiscoverE — Engineering career exploration and free activity library.
discovere.org

→ Your next track

Mechanical Engineering — Coming Soon

Levers, gears, cams, and linkages — how machines convert and transmit force. The next step after structural thinking.

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