Probably the question I get asked the most is “What bridge design holds the most weight?” or “What bridge design is the strongest?”

The answer to that question is not simple and probably is not going to be what you expect. The truth is, I cannot answer the question. There are too many variables that [...]

Not all popsicle sticks are equal

If you have been given a project of building a popsicle stick bridge, there is something you should know. Probably one half of the popsicle sticks that come from Wal-Mart or other store are bent, twisted, or otherwise deformed. And obviously deformed popsicle sticks won’t be as strong as straight [...]

Now Updated and Expanded
I wrote an ebook, 5 Steps to Building a Model Bridge PDF to answer the most common questions people have about building bridges. In the ebook I show all the steps of building a model bridge, and then walk people through the actual construction of a bridge. The ebook contains many photos [...]

Lateral What? Exactly. Perhaps the most important aspect of your bridge and you aren’t sure what it is.

Lateral bracing is the term I use to refer to any pieces on a bridge that help keep the top chord from bending horizontally. In the figure before, lateral bracing is red:

Why is lateral bracing so important?
As you [...]

How Changing Height Affects a Bridge
I found it slightly difficult to come up with the right title for this post. Perhaps a better one is What happens when you change the height of a bridge assuming nothing else changes. I am talking about the forces that act on a bridge, of course.
I get asked all [...]

Here I have complied what I believe to be the best list of websites that you will find useful. All of them have relevant model structure, bridge and tower information, some sell balsa and basswood, and others contain useful tips. Some of these sites have a specific competition or goal in mind, but you can [...]

1. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice.
2. Go easy with the glue bottle. As a general rule of thumb, if you can see it than you are using too much.
3. Keep your hands clean! Oils and grease from your skin [...]

An L-beam is more efficient than a square the same width. It is not going to hold as much, but it is going to be more efficient. An L-beam is also more efficient than a square with the same mass of wood. Of course, you have to count in the glue weight for an L-beam.Balsa, [...]

Compression:
Compression is a pushing (compressing) force. You can take the middle a straw and squeeze it between two fingers, the straw flattens. However, if you hold each end of a straw and push together it is harder to make the straw compress, or flatten. The shorter a piece of wood is, the more compression it [...]

I built this bridge for the 2005 Fernbank Science Center bridge design event. This is the strongest bridge I have ever built. The bridge spanned 16 inches, weighed 37 grams, and held 346 pounds. That puts its efficiency over 4200! I had never even come close to getting this amount of strength out of a [...]

Common trusses used in engineering:
Warren

Pratt

Howe

K Truss

The following figures are shown under a load. The numbers represent percentage, where the total load = 100. The numbers are rounded to the nearest 5. For absolute numbers, visit the Bridge Designer.
Red represents tension, blue represents compression, and green is no load.

On this Warren truss, each of the [...]

There are several ways to test model bridges:

With a machine
By pouring sand
Textbooks
Pushing down on your bridge

Using a machine

Obviously, if a machine is being used to test your bridge, there isn’t a lot you can do. You can stand watching the destruction of your bridge. Or turn away and cover your eyes with your hands. I [...]