Cable-stayed bridge can experience large amplitude stay ascillations under certain conditions of combined traffic flow and rain-wind loads. Previous analyses of actual field test data have demonstrated that the abrupt shift in vibration modes can be associated with nonlinier chaotic behaviour. To investigate this effect, this study developed a highly realistic nonlinier finite element model using LSDYNA of a typical cable-stayed bridge based on thr design oh the Bill Emerson Memorial Bridge at Cape Girardeau, MO. Simulation oh the dynamic responses of the stay cable under complex traffic flow loads generated an extensive data set which was then analyzed using the CTRB sofware. The results show that even in absence of raid-wind excitations, thr bridge deck may exhibit chaotic behaviour that could excite the stay cable into a strong chaotic regime. These numerical results will be compared to actual monitoring data from a sensor network on the bridge after it is put into service.