A note on dynamic fracture of the bridge bearing due to the great Hanshin–Awaji earthquake

The great Hanshin–Awaji earthquake, which occurred in Japan in 1995, caused fracture and destruction of a large number of structures. One of the examples, whose mechanism is not clear, is the fracture of a bridge bearing part of the Nielsen bridge type that does not occur under ordinary static or dynamic loading. The fracture probably resulted from a very high stress due to an unexpected dynamic mechanism or an impact. In this paper, the three dimensional dynamic behaviour of a bridge of the Nielsen bridge type was analysed, for a collision/impact between the upper and the lower bridge bearings, which might have occurred in the great Hanshin–Awaji earthquake. The numerical results show that an impact due to a relative velocity of 5–6 m/s between the upper and the lower bridge bearings generates a stress sufficient to lead to the fracture in the upper bridge bearing. The location and the direction of the maximum principal stress determined numerically in the upper bridge bearing coincide fairly well with the observed features of the actual fracture plane.