2. Theoretical Background
2.1. Sign Conventions in STAAD Pro
The following sign rules have been considered to extract the loads from STAAD Pro:
- Axial (FX): the positive sign of the force corresponds to the direction of the X local axis
- Shear-Y (FY): the positive sign of the force corresponds to the direction of the Y local axis for the member
- Shear-Z (FZ): the positive sign of the force indicates alignment with the direction of the Z local axis for the member
Axial forces:
- A positive value at the start node indicates compression at that start node.
- A positive value at the end node indicates tension at that end node.
- A negative value at the start node indicates tension at that start node.
- A negative value at the end node indicates compression at that end node.
The member end moments (MX, MY and MZ) follow the “right hand rule”. If the right hand thumb points the positive local axis, then the fingers point in the direction of the positive moment. The following figure shows the positive member end moments.
- Torsion (MX): the positive sign of the force determines the counterclockwise action, seen from the end of axis X, on the section corresponding to the end of the member.
- Moments (MY, MZ):: the positive sign of the force represents a counterclockwise action when viewed from the end of the Y or Z axis on the section corresponding to the end of the member.
2.2. Conventions in IdeaStatiCa
The following sign conventions are used to represent loads in IdeaStatiCa:
- Axial forces (FX): Positive = Along local X axis, Negative = Opposite to local X axis.
- Shear forces (FY, FZ):: Positive = Along respective axis (Y or Z) in the specified direction, Negative = Opposite to the respective axis direction.
- Torsion (MX): : The positive sign of the force determines the counterclockwise action, seen from the end of axis X, on the section corresponding to the end of the member.
- Moments (MY, MZ):: The positive sign of the force represents a counterclockwise action when viewed from the end of the Y or Z axis on the section corresponding to the end of the member.
Axial forces:Positive values indicates tension.
2.3. Adjustments for Compatibility between STAAD and IdeaStatiCa
Changes were made for STAAD inputs to ensure the loads are compatible with IdeaStatiCa for further analysis:
- Axial forces at the start of the STAAD element must be reversed. This ensures that the sign conventions in STAAD (compression at the start node) are aligned with the reversed expectations in IdeaStatiCa.
- Vertical shear forces at the end of the STAAD element must be reversed.This ensures correct shear distribution and alignment with the local axis conventions used in IdeaStatiCa.
- Vertical bending moment at the start of the STAAD element must be reversed. IdeaStatiCa considers the moment directions in a reversed orientation compared to STAAD for compatibility in further calculations.