Engineering Balsa Bridges By eli laby (the one with big hair)

The History of Bridges


In the beginning of bridges, they had short spans usually crossing creeks or rivers. They were also made from naturally occurring materials such as; wooden logs and sticks, stone, dirt, etc. Revolution in the bridge making sense occured in Ancient Rome when they discovered that ground up volcanic rock make very good mortar. The Romans also started the use of arches. The arches held weight very well, and were able to be lighter and stronger than previous bridges. In the 1800's cast iron, which sadly couldn't carry as much weight, but it helped in the invention of steel.

Old arch bridge


Modern bridges are MUCH stronger than past bridges. The invention of concrete has made them very hardy. This is because concrete erodes MUCH slower than dirt and wood. Modern bridges also use cables to support bridges. Today, bridges can be very long, and can span in between countries, across seas, over valleys.

New suspension bridge


Bridges of the future are expected to be different than bridges of today in the following categories; materials, construction processes, and modeling. Computers are getting more an more capable of designing bridges. This means that if computer can calculate the angles and engineering generally, then bridges will be faster to make. People also expect to see stronger and more durable concrete and other materials. Inundeveloped countries bridges are going to pop up all over the place.

Types/styles 0f bridges

Suspension Bridges

Suspension Bridges are a type of bridges where there are suspension cables in between towers. Suspension cables are tethered at the ends of the bridge. They also carry most of the weight.


Arch Bridges

Arch bridges have been around for almost 3000 years. That were popular until steel was invented, steel is more efficient. They are still used though. These were popularized by the Ancient Romans.

Arch bridge

Truss Bridge

A truss bridge is made of connected elements shaped into triangular sections. It transfers the load to a wider area, letting heavier loads use them. They used to be made of wood. Now the are mostly made of metal.

Truss Bridge

My Bridge

March 29, 2017

Today I finished my concept, design, and working drawings.

March 30, 2017

Today we need to decide which design to use. We decided on mine, the bottom one. We decided on it becuase it left us more wood for cross beams. We also started our top view.

Peg box thingy!
Our 20 feet of wood
Wood cutter

March 31, 2017

Today we need to finishe our top/bottom view and start working on our bridge. Today we finished our top/bottom drawing and started working on our first side.

April 3, 2017

Today we need to keep working on our first side. Today we finished our first truss.

Our first truss!

April 4, 2017

Today we need to start working on our second side or truss. Today we finished most of our second truss.

Our second truss! My partner got in the way of the picture.

April 5, 2017

Today we need to finish our second truss. Today we finished our second truss and attached our trusses together at the ends.

The wooooood glue is soooooooo colorful!

April 6 & 7, 2017

I was absent these days and my partner did not take pictures.

April 10, 2017

Here is what our bridge looks like.

All done!

Next, we hooked our bridge onto the bucket.


Then we tested our bridge!

April 11, 2017

Today we repaired our bridge by glueing extra pieces of wood with a gallon of glue/mayonnaise.


Created with images by Martin L H - "bridge" • Jonas B - "Bridge" • FelixMittermeier - "starry sky night photograph night sky" • JamesDeMers - "bridge japanese garden arch" • Stirling Council - "Stirling Old Bridge" • gajman - "Brooklyn Bridge" • Wonderlane - "The many cameras and lights on steel girders over the 520 Floating bridge, view of the Olympic mountains, U District buildings, Bellevue to Seattle, Washington, USA" • ♡ dare to share beauty - "Golden Dawn Bridge - HDR" • m01229 - "Stone Arch Bridge" • tsaiproject - "Alexandra Bridge"

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