Abstract: Using modal decomposition method for solving vehicle-bridge coupling equation to analyze the dynamic response of the simply-supported beam bridge to different vehicle load and speed.The half car model was used  as vehicle,and  Euler-Bernoulli beam was used as the simply-supported beam bridge.Using the ANSYS software,the simply-supported beam bridge span deflection curve was obtained.The results show that vehicle load increase  made the bridge span deflection increase;the beam’s span deflections were 0.028 m and 0.049 m respectively  in the  standard vehicle load and 100% vehicle overload.As the vehicle speed increased,the simply-supported beam bridge span deflection reached at its peak value at the vehicle speed of 60 km/h and vehicle-bridge resonance was resulted in.

Key words: dynamic response, vehicle-bridge coupling equation, half car model, load and speed