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FAQ 004223 | The load distribution in RFEM shows unstressed FE elements in the middle of the mode...

Figure 01 - Left: RFEM Model | Right: Wind Load Distribution on Individual FE Elements

Figure 02 - Left: Wind Pressure on Structure | Right: Simplified Model

Figure 03 - Setting Level of Detail in RWIND Simulation (Left) and in RFEM (Right)

Figure 04 - Model with Higher Level of Detail and Results

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004223

Finite Element Analysis

The load distribution in RFEM shows unstressed FE elements in the middle of the model for the loads from RWIND Simulation. Why?

Answer

There is no load distribution displayed between the external facade elements in the example shown in Figure 01. The unstressed cells are not displayed according to the color scale for the load distribution, but remain empty. Thus, the value on these elements is 0. This has the advantage that it is recognized immediately that the FE elements are not subjected to a load.

Figure 01 - Left: RFEM Model | Right: Wind Load Distribution on Individual FE Elements

The cause of the problem can be visualized directly in RWIND Simulation. By default, the calculations are based on a simplified model there. Depending on the setting, the shell of the model can be refined or coarsened. An FE mesh is placed over the structure and depending on the level of the detail, this FE mesh clings to the model. Figure 02 shows the extent of the level of detail that is too small. The surfaces standing on the façade are not displayed well enough and no wind flows between the cantilevered surfaces in the simulation, which is why these internal surfaces are not subjected to any wind pressure.

Figure 02 - Left: Wind Pressure on Structure | Right: Simplified Model

The level of detail can be adjusted in RWIND Simulation via "Edit Model" or directly in RFEM in the settings for the wind load simulation (see Figure 03). Optionally, the simplified model can also be deactivated completely in RWIND Simulation.

Figure 03 - Setting Level of Detail in RWIND Simulation (Left) and in RFEM (Right)

In the case of a higher level of detail (corresponds to a finer FE mesh), the cantilevered surfaces are displayed cleanly and the FE elements are stressed accordingly (see Figure 04 and Figure 05).

Figure 04 - Model with Higher Level of Detail and Results