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I have the following problem occurring in RF-/FF-LTB: To analyze the effect on the load application point, I have defined the eccentricity e-z one time positively and another time negatively. A positive value, which means a load application on the lower chord, should be a contribution to the stabilization of the structural system. But this is not the case. What do I have to do?

Answer

The definition of the load application point in RF-/FE-LTB depends on the local member axis system. Define, for example, For example, if a horizontal member (global Z-axis is pointing downwards), the axis z of the local axis system is also pointing downwards in the positive Z-direction. If you want the load to act on the top side, enter a negative value for ez. For a horizontal member, it does not matter in which direction the member direction runs, the local axis z always points downwards.

The situation is different for a vertical member. In this case, the member direction runs from top to bottom and the local axis z of the local axis system points in the negative X-direction. If a positive value is entered for the eccentricity ez, this corresponds to a load application on the upper chord and thus leads to a greater utilization.

You can activate the display of the local axis system of each member in the "Display" navigator by activating the option "Member Axis Systems x, y, z" under "Model" -> "Members".

Keywords

load application point Eccentricity Axis system

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