The Howe truss

William Howe, from Spencer, Massachusetts, patented his truss design in 1840. The Howe Truss
combines diagonal (timber) compression members with vertical (steel rod) tension members. Its
impressive strength over long spans makes it very popular as a railroad bridge.

The load (train track) can be placed across either the top chord or the bottom chord of the truss.
When the load is at the top, as it is in my bridge, it's known as a deck truss.
When the load is at the bottom it's known as a thru truss.