Asnachinda P., Pinkaew T.

ABSTRACT : In the design of bridges, the design live loads generally have been determined using impact factors or dynamic load factors as multipliers of the nominal static loads. The influence of the bridge’s continuity on the impact factor is studied. The main objective is to investigate the variation of the impact factor due to the change of the degree of bridge’s continuity. The continuous bridge is considered using three spans of the simple beams interconnected by the link slab at the supports. The finite element method is employed to model the bridge. The vehicle is modeled using a moving four-degree of freedom dynamic system. Then the vehicle model and the bridge model are interacted through the bridge surface roughness. Numerical examples and comparisons of various vehicle mass, vehicle speeds, bridge span length and degree of continuities are presented. Based on the numerical examples, the impact factor is found to significantly influence on the bridge continuity. The obtained results from simulations indicate that the application of the existing design codes would under estimate the impact factor and consequently lead to the unsafe design of the bridge against live load. Finally, to avoid this undesirable estimation of the impact factor, the author’s recommendations for the practical design are given. KEYWORDS : Impact factor, Dynamic load factor, Bridge continuities, Vehicle-bridge interaction