This paper investigates the evolution of the wheel-rail contact forces in high-speed railway bridges during resonance situations. Based on a dimensionless formulation of the equations of motion, a parametric study is conducted and the fundamental parameters influencing the contact forces are brought to light. The bridge is idealised as an Euler-Bernoulli beam, while the train is simulated by a system of rigid bodies, springs and dampers. The situations such that a severe reduction of the contact force could take place are identified and compared with actual bridges. Finally, a real case is analysed and checked against the theoretical model.