Moment capacity (Beams: BS 5950)
The moment capacity check is performed according to BS 5950-1: 2000 Clause 4.2.5 for the moment about the x-x axis (Mx) and about the y-y axis (My), at the point under consideration. The moment capacity can be influenced by the magnitude of the shear force (“low shear” and “high shear” conditions). The maximum absolute shear to either side of a point load is examined to determine the correct condition for the moment capacity in that direction.
Note: Not all cases of high shear in
two directions combined with moments in two directions along with axial load are
considered thoroughly by BS 5950-1: 2000. The following approach is adopted by
Tekla Structural Designer:
- if high shear is present in one axis or both axes and axial load is also present, the cross-section capacity check is given a Beyond Scope status. The message associated with this status is “High shear and axial load are present, additional hand calculations are required for cross-section capacity to Annex H.3”. Tekla Structural Designer does not perform any calculations for this condition.
- if high shear and moment is present in both axes and there is no axial load (“biaxial bending”) the cross-section capacity check is given a Beyond Scope status and the associated message is, “High shear present normal to the y-y axis, no calculations are performed for this condition.”
- if high shear is present normal to the y-y axis and there is no axial load, the y-y moment check and the cross-section capacity check are each given Beyond Scope statuses. The message associated with this condition is, “High shear present normal to the y-y axis, no calculations are performed for this condition.”