Real Life Deflection Vs FEA – Model Verification

Real Life Structural Model Verification

Ever wondered how close an FEA analysis model is to real life? Today we will be comparing the results of an analysis model to a real life beam and a measured result - in this case deflection. The experiment was run by a SkyCiv User who wanted to verify the Structural Analysis, not only with another model, but also with a real life result that could be measured.

measurement

Model Setup

The model was a 15.516m span simply supported concrete beam under a self weight. There were two models setup - a simplified profile (assumed to be rectangular) and a more detailed custom shape that was built in the SkyCiv Section Builder. The beam lengths and forces can be seen as follows:

beam-span

SkyCiv Beam

SkyCiv Beam uses FEA analysis to calculate a single span member. In this case, SkyCiv Beam produced a negative deflection of 69.754mm, with a simplified rectangular cross section, which is shown in the 3D renderer below:

SkyCiv Structural 3D

With a more accurate representation of the cross section, the SkyCiv Structural 3D produced a result of 66.748mm. This was again under the beam's self weight, and using 25 evaluation points. The results and Analysis report are shown below:

deflection-beam-wireframe
deflection-verification
View Structural 3D Analysis Report

Practical Result

Using a tight piece of string, this SkyCiv user measured a max deflection from the string line to the top of the beam. The deflection result measured at 65 mm.

Summary of Results

Below are the tabulated results of this experiment, comparing the results of an FEA model and it's real life result. The results show the FEA results are slightly overstated and, in this case, fairly conservative in comparison to the actual result. This is an extremely simplified model as we are using a single line element, and only breaking it up into 25 elements. A more accurate FEA would be a plate or brick FEA model. However for a model this simple, this adds a lot of complexity and would take a lot longer to model, for a slightly more accurate result.

For structural engineering, a 2D element is a perfect combination of speed an accuracy. Taking minutes to setup, but still gets within 3% accuracy of a real life result which is more than enough for general structural analysis application.

Measurement Result Deviation Notes
Real Life 65mm - -
SkyCiv Beam 69.754mm 6.8% Simplified (Rect) Section
SkyCiv Structural 3D 66.748mm 2.6% -