Document Type: FAQ
Product(s): LEAP BRIDGE STEEL
Original Author: Bentley Technical Support Group -VM
QUESTION: LEAP Bridge Steel is presenting output results in a global vs. local coordinate, please clarify?
For member forces and moments, the program is using local axis and for displacement it is using global axis.
The reactions are presented along a modified global axis system whose x axis is tangential to the girder path at the point of the support pointing towards the end of the bridge; y is vertically upward and the z is along the direction of vector resulting from cross product of x and y axis.
The girder forces are presented about the girder local axis which is pretty much same as axis of reporting for reaction – x is tangential to the girder path pointing to the end of the girder; y is vertically upward and z is vector resulting from cross product of x and y axis.
Following is to depict on a plan view where vertical axis (y) is pointing towards us.
Attached picture shows the co-ordinate system used by LBS for member forces and moments (local axis).