集鹿大橋 (Ji Ji Da Qiao)

In General:

This is a PC cable stayed bridge under construction near the epicenter. The structure consists of three parts, a central part sustained by cable tendons from an RC pylon and continuous girders at both sides. The central part was originally connected to the side girders by PC tendons, but the tendons were broken and both side-girders dropped from the shoes at the connected parts. The top of the support piers located at both ends of the central part was crushed a little. The side continuous girders must have been thrust in the longitudinal direction during ground movement.
The pylon had flexural and torsional cracks with spall off of cover concrete above the PC girder. One stay cable was broken.

Diagnosis:

Looking at the overall damage, the girder of the central part might have rotated horizontally at the pylon and lead to the breakage of PC tendons which connected the central part to the side girders. The ends of side girders moved laterally from the original position.
The girders were not so seriously damaged. The pylon was also slightly damaged and could be retrofitted easily by wrapping with steel plate or continuous fiber sheets.

[Comment from Prof. J.C. Chern]
The manager of T. Y. Lin Co. mentioned that the construction company just took away the tower crane, which located at the empty hole near the pylon. This is the major reason why it vibrated so much during the great earthquake.

Suggestions:

Dynamic analysis is strongly recommended to examine structural behavior during the earthquake movement. It can reveal what had happened during the earthquake and tell us what we should do to improve the design of this type of structure.