Question
What is the difference between setting and not setting the nodal local axis in a steel box curved bridge? Also, how should the nodal local axis be set?
In the case of a straight bridge, the unit load in the Y-direction would act on the steel box girder bridge, but the nodal load seems to be applied strangely. Additionally, the support point direction is set to Global, which seems to change the direction of constraints in a curved bridge.
Answer
Nodal Load is entered based on the global coordinate system, regardless of the node local axis.
Loads that do not align with the axis direction of the global coordinate system must be entered as components in each direction. For ease of input, loads can be entered in a formulaic manner (e.g., 30*sin(30)).
For supports, if a nodal coordinate system is defined, the movement and constraint directions are applied based on the nodal coordinate system. Therefore, the presence or absence of a nodal coordinate system definition can alter the analysis results.