Pratt Truss Roof Details

Pratt trusses are commonly used in long span buildings ranging from 20 to 100 m in span.

Pratt truss roof details.

This type of truss is used where gravity loads are predominant see below left. These can vary a lot. I think this does give the pratt an advantage but read my best bridge design article more for information. This article and series of illustrated diagrams shows you all the parts of a basic roof truss king truss and queen truss.

There are six main types of roof trusses as listed below. This particular type of truss offers some interesting features mainly thanks to the fact that the vertical members provide tension while the diagonal ones are bringing in compression. There are many types of roof trusses as wall as many types of roofs more types than there are parts. It can be used for spans from 6 10m.

The truss framed system tfs is a new light frame wood construction concept that inte grates customary construction components roof trusses floor trusses and wall studs into unitized frames. Flat truss with cantilever pratt configuration top chord bearing flat truss pratt configuration fl att rus w e nc of ig s l op i ngp are ch ds h w f u t sloping top chord howe configuration floor truss system 42 modified warren configuration mono trusses scissors mono mono parts of a truss framed roof gable end valley set gi rde. Vertical members are tension and diagonal members are compression. The roof truss structure and design is integral to roof structural integrity and shape.

For further details on how the loads are calculated on a truss and other design details please read this. Pratt truss pratt truss is made of steel. Roof truss span tables alpine engineered products 15 top chord 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 bottom chord 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2 12 24 24 33 27 27 37 31 31 43 33 33 46 2 5 12 29 29 39 33 33 45 37 38 52 39 40 55 3 12 34 34 46 37 39 53 40 44 60 43 46 64 3 5 12 39 39 53 41 44 61 44 50 65 47 52 70. It used wood for the vertical members.

In a conventional pratt truss diagonal members are in tension for gravity loads. The ones in the photo above are in a heritage building of around the 1950 s fannie bay gaol darwin nt. A roof truss based on two pratt trusses and a bottom chord. These are very economical form of roof trusses.

The roots of the pratt truss involved using iron not wood for the angled members. However with most model bridges you are just using wood. Better yet build your own pratt and howe truss bridges and compare their strength on your own. Fan truss it is made of steel.