STUDY ON FLOOD ACTION MECHANISM AND FLOOD RESISTANCE OF HIGHWAY GIRDER BRIDGE SUPERSTRUCTURE

Flood is a serious threat to the bridge across the river, the direct acting force of flood on a bridge is the impact of water. In the past, the flood action on bridge superstructure above water level was neglected in bridge design, which results in the insufficient flood resistance of bridge superstructure. Based on mechanical properties of flood water, it studies the action mechanism of flood on bridge superstructure and puts forward the calculation formula of flood damage force and the determination method of related parameters; and then analyzes the main failure mode of superstructure under the action of flood. The results show that the bridge superstructure is mainly affected by horizontal impact force, vertical buoyancy force and uplift force under the action of flood; the failure modes of the superstructure include sliding of bearing, shear of bearing and overall overturning. On this basis, according to the balance and stability theory between the flood damage and structural resistance, the design method and calculation formula of the bridge superstructure subjected to failure modes of bearing sliding failure, bearing shear failure and overall overturning are proposed. The results can be used for the flood prevention design and safety assessment of highway bridges.