Joints for Bridge Building

To build a bridge you must join many separate pieces. The stronger the joint, the stronger the bridge. We are going to view several methods of joining your bridge together. Butted Joint Scarf Joint Lap Joint Half-Lap Joint Lamination Notched Joint Beveled Joint

Butted Joint A Butt joint is the weakest type of joint. Two pieces of wood joined at the ends, do not support each other. All that holds them together is the glue.

Scarf Joint Scarf joints do provide more support. If a force were applied downward on this joint, one piece of wood, would press against another adding strength.

Lap Joint The more two pieces of wood overlap, the more they can help each other. The dotted line represents a pin. A pin prevents the two pieces of wood from pulling apart.

Half-Lap Joint This is one of the strongest types of joints.

Lamination Lamination adds weight, but can provide huge amounts of support.

Notched Joint Notching locks pieces together and adds strength.

Beveled Joint Tight fitting beveled joints prevent gaps and spaces that weaken the bridge. Beveled pieces can be pinned also.

View the next few slides for construction techniques used on a real bridge. Can you determine the construction technique they used? construction technique they used?

Photo By: Doug Porter 1

This is a half-lap joint 1

Photo By: Doug Porter 2

This joint combines a notch and a bevel 2

Photo By: Doug Porter 3

This joint show an excellent example of lamination. Pins and bolts were used to hold the boards together 3

Photo By: Doug Porter 4

Here is an example of lap joints 4

Photo By: Doug Porter 5

These joints show a butted joint and a notched joint side by side 5

Putting it all Together Joining the trusses and adding the deck Photo By: Doug Porter

Putting it all Together Beveled and Notched Joints Photo By: Doug Porter

Putting it all Together Lap, Bevel and Notch Joints Photo By: Doug Porter

Putting it all Together Photo By: Doug Porter

Testing your Bridges