Designing a Truss: Calculating Forces & Loads

In summary, for the Civil engineering project, a truss needs to be designed with calculations for forces using method of sections and method of joints. The truss is 45 meters long, 2.5 meters high, and 2.5 meters wide with a span to depth ratio of 18 and a Θ of 45 degrees. Considerations for roofing, ancillary member weight, truss self weight, and live load under Australian Standards must be taken into account. The total dead load is 40.23kN for truss self weight, 8.046kN for ancillary members, 2.275kN for roofing and slab at 135kN, resulting in a DL of 4.
  • #1
SteliosVas
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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 :(
 
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  • #2
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.
 

1) What is a truss and what is its purpose?

A truss is a structural framework made up of interconnected beams or bars that are designed to support loads. Its purpose is to distribute the weight of the load evenly across its members and transfer it to the supports, thus providing stability and strength to a structure.

2) How do you calculate the forces in a truss?

To calculate the forces in a truss, you will need to use the method of joints and method of sections. The method of joints involves analyzing the forces at each joint in the truss, while the method of sections involves cutting through the truss to isolate specific members and analyzing the forces acting on them. Both methods use the principles of equilibrium and the laws of physics to determine the forces in each member.

3) What are the different types of loads that can act on a truss?

The different types of loads that can act on a truss include dead loads, live loads, wind loads, and seismic loads. Dead loads are the weight of the structure and any fixed elements attached to it. Live loads are the weight of people, furniture, and other movable items. Wind loads are caused by the force of wind on the structure. Seismic loads are caused by earthquakes or other ground movements.

4) How do you design a truss to withstand a specific load?

To design a truss to withstand a specific load, you will need to calculate the maximum load that the truss will need to support. This will involve determining the required strength and stiffness of each member in the truss. You will also need to consider the type of load (e.g. dead, live, wind, seismic) and its direction and magnitude. Using this information, you can select the appropriate materials and dimensions for each member to ensure that the truss can withstand the specified load.

5) What factors should be considered when designing a truss?

When designing a truss, several factors should be considered, including the type and magnitude of the load, the direction of the load, the materials and dimensions of the truss members, the stability and rigidity of the structure, and any applicable building codes and safety regulations. It is also important to consider the cost and time constraints of the project and make any necessary adjustments to the design to meet these requirements.

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