Designing a Truss: Calculating Forces & Loads

[SteliosVas]

Homework Statement

So we have to design a truss for our Civil engineering project, calculate forces in members using method of sections and method of joints.
However as both trusses are symmetrical we only need to take one of them

The truss is 45 meters long, 2.5 meters high, and 2.5 meters wide. This gives us a span to depth ratio of 18. It also gives us a Θ for each truss at 45degrees. Now we must consider roofing, ancillary member weight, truss self weight and live load for roofing under Australian Standards

Okay so basically the total dead loads are:

40.23kN for Truss self weight, 8.046kN for Ancillary Members, 2.275kN for roofing and slab at 135kN.

Giving us a DL of 4.1233kN/m

For Live load we get 281.25kPa for the Australian standard and 0.024kN for Live Load (Under Standard)

Giving us a LL of 6.2505kN/m

There are 9 sections (to the midpoint, each 2.5 meters long) and 18 in the full truss (one of the two).

Homework Equations

Now I do not understand completely how to work out the internal forces, and where to begin with method of section and joints.

The Attempt at a Solution

Not sure :(

 

[Slash_ZA]

If I were you I would ask a truss plant to run the design in Mitek software(we also have it in South Africa) ask them to print thebcalcs and then compare that to your calculations. In principle the truss will not work as the span is too big and the height will be a teansport problem but just to get calcs they can give it a shot.