Limit state equations for circular cross sections subjected to combined loading

• The behaviour of circular cross section under combined loading of axial force, bending moment, internal pressure and torsion is analyzed.
• Load interaction equations for circular cross sections for the elastic limit state have been formulated.
• FEA is carried out to check the validation of the results obtained from proposed formulae.
• The proposed formulae give quick and accurate results about the strength utilization of the circular cross section to resist the applied loads.
• The error between analytical and FEA results is within 4% accuracy.

Quick information about the capacity of any cross section for combined loading is very useful information at the early stages of engineering design. These combined loads can be pressure, axial force, bending moment and torsion, depending on application of cross section. Interaction formula based on limit loads is a very useful equation to estimate the capacity of any cross section for a combination of loads. For hollow circular cross section the complexity of interaction formulae depends on definition of limit state and type of loads. Interaction formulae for circular cross section with different limit state assumptions are easily available in literature for pressure, axial force and bending moment. This paper proposes interaction formulae for circular cross section with additional term of torsional moment at elastic limit load.