For more info: 021 55734344

Home / Products

SE 110.22 Forces in an overdeterminate truss



  • Comparison of forces in statically determinate and overdeterminate trusses1
  • Bars with strain gauge full bridges to measure bar force


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


[1] investigation of bar forces in statically overdeterminate trusses
[2] surplus bar, longitudinally adjustable
[3] straight and inclined loading possible
[4] strain gauge to measure force on each bar
[5] measuring amplifier FL 151 required
[6] software in FL 151 to evaluate measurement data
[7] storage system to house the components
[8] experimental setup in frame SE 112

Technical Data

Bars: 8
- 5 bars, fixed 300mm
- 2 bars, fixed 424mm
- 1 bar, adjustable 400...450mm
- angle between bars: 30°, 45°, 60°, 90°
- maximum bar force: 500N
- strain gauge on each bar
- height of truss max. 270mm
- length of truss max. 500mm

Load application device
 -500...+500N, graduations: 10N

Dial gauge: measurement range: 0...20mm

Dimensions and Weight
LxWxH: 1170x480x178mm (storage system)
Weight: approx. 22kg (total)
Scope of Delivery 1 set of bars
5 node discs
1 load application device
1 set of cables
1 storage system with foam inlay
1 set of instructional material

Subscribe now