DESCRIPTION

Technical Description

Overdeterminate trusses are employed where overdimensioning is purposely required because safety must be maintained in the event of failure of an element, such as in aircraft construction. With additionally inserted bars a statically determinate truss becomes internally statically indeterminate. In this case the truss is termed statically overdeterminate. 

The SE 110.22 experimental setup permits investigation and comparison of statically determinate and statically indeterminate trusses. Using the bars and node discs, a statically determinate, single plane truss is first constructed. On installation of a surplus bar the truss becomes overdeterminate. By way of a load application device, straight or inclined forces are applied to the truss, thereby simulating various load cases. The occurring tensile and compressive forces in the bars are recorded by means of strain gauges. 

Computerised evaluation is provided by measuring amplifier FL 151. The software in FL 151 is used to manage the measurement data and provide graphical representation of the bar forces. The software features a comprehensive help function.

All the component elements of the experiment are clearly laid-out and housed securely in a storage system. The complete experimental setup 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

- measurement of the bar forces in a statically determinate and statically overdeterminate, single plane truss
- distribution of forces in the single plane truss dependent on the use of a surplus bar
- dependency of the bar forces on the external force
  * magnitude, direction, point of application
- comparison of measurement results with mathematical methods
  * method of joints
  * Ritter’s method of sections
- basic principle: measurement of forces using strain gauges