This bridge was built by Michael in Quebec.

I have a bridge I built for a physics for engineers class I’m taking in cegep (QUEBEC). My partner and I didn’t have much confidence in it, but it blew the competition away! The design was a fairly straightforward arch as you can see. We primarily focused on keeping the weight of the bridge down. The bridge weighed in at 211 grams.

The efficiency rating worked as follows:
Weight supported by the bridge divided by the weight of the bridge squared.

This was our score. 173 KG./ (.211)squared. Our score was 3886, second place was 2100 and the rest of the competition was well below 2000. Our bridge held 381 pounds! And the lab class which we tested them in ran out of weight for us to load it with, so we couldn’t break the bridge! our teacher is building a hydraulic system to crush it next week!
~Michael.

These are some pictures of a bridge I built mainly out of boredom, but also since I have an interest in engineering. It’s a large cantilever bridge, meaning it has two arms that extend beyond their piers that hold up a center suspended span. It’s 10′ 2″ long and as of right now is hanging across my bedroom ceiling. One nice thing about cantilever bridges is how the longer top-chord is in tension, while the shorter, straight bottom chord is in compression.

The bridge was built using both sizes of popsicle/craft sticks held together with high-temperature hot melt glue. In the pictures (on my Photobucket, as Wordpress wanted to crop them down too far) you can see the I-beams made out of sticks and made into the chords, diagonals and bracing. Two of the trusses were built by “building up” girders rather than making I-beams. The top-chord lateral bracing is different on the one cantilever arm, as it was built earlier in the year and I came up with the idea for the other bracing in the downtime.

For decoration I added blue LED lights to the bridge.

See more pictures at the Photobucket Album.

Youtube video of the bridge test

The design procedure was completed over a 2 week period allowing sufficient time for segment to dry before moving onto the next. Heavy duty pegs were used to fasten the joints that had already been sanded to allow for maximum strength in the joints.

As the design took shape, I made several smaller models and tested the joints to come up with a final design for the joints that would allow for more weight to be added before the joints failed. Failure in the joints would mean that it wasn’t the truss design that caused the failure, but a failure in the construction of the truss.

After allowing 24 hours for the 1 layer truss to dry the pegs were then removed. As the image illustrates the truss consists of one smaller heavily layered triangle and 2 larger reinforced triangles. The top side when under a pinpoint force will be under compression and the bottom tension. The central joint that will be directly under the metal element issuing the force was to be constructed so that the glue joins if they were to fail would not be able to move due to the surrounding sticks creating a ‘nest’ for the failed member.

The original design was to be compiled of 12 layers each consisting of 18-19 sticks. But after weighing the truss structure it was calculated that the truss would have a final weight of over 300grams which would lead to a decrease in efficiency. This was therefore reduced to an 8 layer truss that weighed 220 grams.

When designing the truss care was taken into using sticks that were not only straight but did not contain any knots or weak points, these sticks were discarded.

After the truss was completed all that was needed was to place angled bracing on the truss to stop any bending in the beams under compression. But throughout the whole design efficiency was always key and when bracing was placed on the structure it was placed in selected areas as once again placing sticks in places that was not needed would lead to a decrease in efficiency. Decking was also placed on the end supports to allow for even distribution of force throughout the layers.

The final design structure was 54cm long and 10.5cm wide it had an average depth of 5cm and weighed 220grams.

Nic’s design held a weight of 224kg and had a final efficiency of 1020. It did not shear or snap at any member, but bowed in the second third of member C-E. This member did have angled bracing to stop bowing and this brace did not snap it was only the glue joins in this brace that failed. The truss ballooned out at the point when 2.2kN of force was applied. It was at this point that the test was stopped.

If the experiment was to be completed again I would have braced this area more heavily but from what I had researched I thought the amount of reinforcement already applied would be sufficient as to negate any bowing in this area.

Shows the failure point in Nic’s Design

This popsicle stick bridge was made from 40, unmodified popsicle sticks. The bridge spanned 12 inches, was 4 inches tall and 3 inches wide. I used only Elmer’s white glue to build the bridge. It weighed 57.4 grams (0.13 pounds), and held 90 pounds. Its efficiency score was 712.

This was the first popsicle stick bridge I had ever made, and it turned out to be quite a success. The goal behind this bridge was to design not only a strong bridge, but design a process for building the bridge that could easily be replicated by almost anyone. That is why I didn’t cut any of the popsicle sticks. That alone would add a lot of complexity to the construction of the popsicle bridge.I made the bridge to easily span 12 inches, which seems to be a common requirement in popsicle stick bridge competitions.

Popsicle Stick Bridge Plans

Build This Bridge

I redesigned this bridge from the earlier version. The new one is more efficient. It is also easier to build. I changed the position of only a couple popsicle sticks, and actually took off a few. I found that the average popsicle stick weighed 1.49 grams.

Stronger Version

This bridge uses the same basic design as the one above but doubles the number popsicle sticks in strategic places.

This popsicle bridge was made from 84 unmodified popsicle sticks. It spanned 24 inches, was 4 inches tall and 3 inches wide. I used only Elmer’s white glue to build the bridge. It weighed 118 grams, and held 115 pounds. Its efficiency score was 442.

This bridge is slightly crooked, even though you cannot tell it from this photo. I’m sure that had an affect on its performance. However, this bridge was also tested 5 times. Both my sisters stood on it, and one twice before this picture was taken.

Here is my sister standing on the bridge:

I thought I was making a movie when I tested the bridge, but found out afterward that I hadn’t started the camera. Oh well, maybe next time.

Here are some photos of the broken bridge. None of the popsicle sticks actually broke. Only the joints failed. This is something for me to keep in mind, as it should be very easy to make this bridge a lot stronger.

Get plans for this bridge

Build This Bridge

This is the strongest popsicle bridge I have built so far.

The Destruction

I tested this bridge by putting the edges of the bridge on two books, and then placing a scale on the top of the bridge. Then I slowly lowered myself down on the scale with the help of two chairs. I carefully watched the scale to mark the exact spot of failure.

Before this bridge broke, I did hear several loud “popping” noises. This means several popsicle sticks came unglued. I probably could have stopped testing and re-glued those popsicle sticks. Had I done that, the bridge might have been able to hold even more.

That is the value of pre-testing your bridge. Evidently, a couple popsicle sticks weren’t glued on well enough, at least not as well as the others. That means I had several “weak links” that limit the strength of the bridge. Pre-testing allows you to identify those weak spots and fix them, without completely destroying your bridge.

Get plans for this bridge

Hi, I just wanted to share the excitement…by using ideas from your website (recommended by my son’s Cub Scout leader) my son Jackson and I were able to build a Popsicle bridge with approximately 125 sticks. It set a new record by holding 500 lbs. for about 15 seconds before breaking! Thanks for the great ideas…not bad for the first try! Mark from Fenton, MI