1.5ms 1.698ms 1.863ms 2.233ms 2.599ms 3.33ms Fig.4 Damage process of the synergetic effect Because the blast wave and fragments arrive at the bridge at different time, the failure mechanism of the bridge will change at different moment. The failure process of the bridge is divided into 4 stages in AUTODYN. 1st stage(0.998ms-1.245ms): The fragments arrive at the bridge upper surface, the stress wave begin to spread from the upper surface to the lower border in the beam. The fragments with high speed begin to smash the beam to pieces. 2nd stage(1.245ms-1.698ms): The fragments penetrate the beam further, reaching the longitudinal steels, leading a obvious deformation to the longitudinal steels. And the stress wave spread along the longitudinal steels and stirrups, the stress in the corner of the stirrups become larger. 3rd stage(1.698ms-3.33ms): The crest of the blast wave arrive the bridge surface, encountering with the fragments and effect the beam together. Some local deformations begin to occur in the concrete, and expand towards the lower border of the beam. The mid-span of the beam begin damaged. 4th stage(3.33ms- last ): Because the fragments are crushed in pieces and its speed decreased, the vibrating beam will became static under the remainder blast wave and its own inertia gradually. 4.2 Failure modes contrast
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