The Howe Truss was designed by William Howe in 1840. It used mostly wood in construction and was suitable for longer spans than the Pratt truss. Therefore, it became very popular and was considered one of the best designs for railroad bridges back in the day.
Roof trusses have revolutionized roof framing. A king post truss is a simple, triangular gable truss with a center brace known as the king truss. The truss has four main parts. The top two diagonal pieces that serve as rafters are known as the upper cords.
The Pratt Truss was designed by Thomas and Caleb Pratt in 1844. It became popular for railway bridges because it made good use of iron. The Pratt has many variations, most with their own unique name. For instance, the Baltimore, Pennsylvania, and the Parker are all based off the Pratt.
The Quadrangular Truss The truss shown by Fig. 83 is known as a quadrangular truss, although the more common shape for this truss is that shown by Fig. 87. This truss may be considered as two trussed rafters, held in place by the tie T at the centre.
Queen Post Roof Trusses are very similar in design to king post trusses except that the interior of the truss has two vertical ‘queen posts’ instead of one central ‘king post’. They look great and offer an open area in the middle of the truss. Queen post timber trusses can easily span 30 feet or more when they are spaced around 12 feet apart.