16.2 WHAT ARE TRUSSES?

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Trusses are at the heart of many engineering projects. We can see one of these in the bridge across the grand river.

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Basically, a truss is a collection of beams joined together to carry simple and complex loads.

We can see trusses use in cranes,

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Trusses are typically made from beams that are joined with gusset plates.

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Other times obvious pin joints are used. Consider the pin joint on the end of the tension member below,

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With these types of problems the tension or compression of the beams/members should be clearly indicated. Materials and structures will not fail at the same load when in tension (necking then fracture), than in compression (buckling).

We can see a tension member in a bridge with turnbuckles for tensioning,

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The basic assumptions used in most truss and frame problems are,

1. the joints have pinned ends, so the forces exerted by the beam has a direction that is along the line between pins.

2. Forces are exerted at pins, but no moments.

Types of trusses are shown below,

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Picture of other types of trusses can be seen below,

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Many of the methods in this section can also be extended to the analysis of trusses in 3D.

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16.2.1 References

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Beer, F.P., Johnson, E.R., Statics & Mechanics of Materials, McGraw-Hill, 1992.

Hibbeler, R.C., Engineering Mechanics: Statics and Dynamics, 6th edition, MacMillan Publishing Co., New York, USA, 1992.