Pratt Roof Truss Design

Here is how it looks.

Pratt roof truss design.

The pratt truss structure we will be working with a design called the pratt truss originally designed by thomas and caleb pratt in 1844. Mechanics forces acceleration displacement vectors motion momentum energy of objects and more. This type of truss is used where gravity loads are predominant see below left. Design hub pratt truss design in solidwork.

Pratt truss this is one of the most popular steel roof truss types and it is quite economical. The pratt truss was patented in 1844 by two boston railway engineers caleb pratt and his son thomas willis pratt. The consumption of steel is less in lsm with respect to wsm. While this article focuses on configurations we also have a very cool set of illustrations showcasing the different parts anatomy of roof trusses.

In a conventional pratt truss diagonal members are in tension for gravity loads. American standard steel c channels dimensions and static parameters of. The pratt steel roof truss design is one of the most common designs. A way of making a larger truss out of pre fabricated elements of smaller trusses these roof trusses are simple in design but very effective and cheap to build.

An alternative pratt truss is shown below right where the diagonal members are in tension for uplift loads. The pratt truss design remained popular as bridge designers switched from wood to iron and from iron to steel. In this fashion they form a pattern of interconnected ns. The ones in the photo above are in a heritage building of around the 1950 s fannie bay gaol darwin nt.

The design uses vertical members for compression and diagonal members to respond to tension. Beams and columns deflection and stress moment of inertia section modulus and technical information of beams and columns. This particular 6 section structure has 21 truss members and 12 joints. From above analysis and design of pratt truss following limit state method is more reliable and economical than the working stress method for designing roof trusses for the same configuration of truss total percentage saving in weight of steel is by limit state method is 23 as compare to working stress method.

A roof truss based on two pratt trusses and a bottom chord. Statics loads force and torque beams and columns. Often seen in bridges it features several vertical chords that are connected by a diagonal chord. This chord runs from the top of one chord down to the bottom of the other chord.

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