Whipple Pratt truss
The Whipple Pratt truss, also termed double intersection Pratt truss, added additional diagonals to the basic Pratt truss, which extended across two panels, but kept the parallel top and bottom chords of the simple Pratt profile. Squire Whipple's double intersection truss was patented in 1847. In 1863 John W. Murphy, chief engineer of the Lehigh Valley Railroad, slightly modified the Whipple Pratt truss by adding crossing diagonals. The Whipple Pratt truss was widely used for long span railroad bridges.