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 SE 110.44 Deformation of Trusses
 Technical Description

When a component is placed under load it undergoes elastic deformation. This deformation can be calculated by determining elastic lines for example. Elastic lines describe the deformation of the complete component in the form of a mathematical equation. In reality, it is often only the deformation at specific points on the component which is of interest. Energy methods can be applied to determine these deformations more simply. Castigliano’s first theorem uses energy methods to calculate the deformation of a point on the component. The theorem is applicable to both statically determinate and indeterminate systems.

In SE 110.44 the deformation of a single plane truss at one point is determined using Castigliano’s first theorem. The truss under investigation is made of bars joined together by a articulated construction using node discs. The trusses can be considered as ideal trusses. The bars have special snap-lock fixtures on their ends allowing them to be fixed easily into the node discs. A load application device attached to a node disc generates an external force.

The range of different bar lengths provided permits three forms of truss to be constructed. The bars are made of PVC, so their deformations are clearly visible.
The various elements of the experiment are clearly laid-out and housed securely in a storage system. The complete experimental set-up is arranged in the frame SE 112.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- Elastic deformation of truss under point load
- Calculation of support reaction and bar forces
- Principle of work and strain energy
- Application of Castigliano’s first theorem to
calculate the deformation at a defined point
- Verification of the calculated deformation possible
by the principle of virtual work
- Comparison of the deformations of different trusses