Howe Truss Bridge Design

The Howe truss, a type of bridge design, was invented by William Howe, an American architect.

Similar to Pratt truss's design, it has a distinct difference. Pratt truss uses diagonal beams that run toward the bridge's center. This puts diagonal members of Howe's truss bridge in compression and vertical web members in tension.

William Howe was born May 12, 1803 in Spencer, Massachusetts. After being an apprentice at his father's sawmill in Spencer, Massachusetts, Howe enrolled in the Leicester Academy and graduated in engineering. After many years of building homes and churches, he finally decided to focus his attention on his dream project - building bridges. He also designed the first railroad bridge across the Connecticut River using a unique truss design he had created. Amasa Stone, his employer, purchased the Howe Design for exclusive use in New England. He has since built hundreds of bridges using this design approach. You can also read about the howe truss bridge.

He made many minor improvements to his design, and they were patented under the new Howe Truss in 1846.

William Howe was killed in a carriage accident on September 19, 1852.

Two of William Howe's bridges are still in existence today, in some form.

Jay Bridge A wooden covered bridge that crosses the eastern branch of the Ausable River, Jay, Essex County. New York, USA. Although the original bridge was destroyed by a flood in 1856 it was rebuilt using Howe Truss design the next year. In 1953, the bridge was again damaged. It is now used by cyclists and pedestrians.

Sandy Creek Covered Bridge This 22.7 meter bridge is one of three original Howe Truss bridges still in Missouri. It was built in 1872. The bridge was partially destroyed by floodwaters in 1886 and quickly restored. Sandy Creek Covered Bridge was placed on the National Register of Historic Places (NRHP) in 1970.

Howe Truss in model Bridges

When you think about common truss designs (including the Howe), one thing to remember is that they were created a long while ago. They were created when bridges had to fulfill a particular role and with the available resources. The Pratt, which uses more iron, used more wood in the Howe truss design. The Howe was popularized earlier than iron was cheap to make.

The diagonal members of the Howe truss were made from wooden beams, which were compressed. The vertical members were in tension and used iron (and later, steel). The Pratt Truss was the reverse. Because the diagonal members of the Howe Truss are longer, less expensive iron material was used. It made great use of cheap wood that was readily available.

We use only wood for model bridges. Both our tension and compression members are made from wood. You could also use metal wire or string to make the tension members. The reasons the Howe design was so popular with model builders aren't applicable. While it is a solid engineering design, I prefer the Pratt Truss to the Howe.