Lateral-torsional buckling of a composite beam is observed after fracture of the headed studs and/or cone failure of the concrete slab around the studs occurs. This paper proposes a method to calculate acting forces of the headed studs from the out-of-plane deformation of the beam as a feasibility study to predict the occurrence of such failure of the studs. Equations for calculating the forces of the studs are derived based on the equilibrium of sectional forces in a free body ofH-shaped steel beam taken from a composite beam. The validity of the proposed equations is confirmed by comparing FEA that can reproduce the previous loading test of a composite beam.
