A study on damage assessment of the scoured bridges

Abstract

Throughout the past decade, scoured bridges in Taiwan have frequently collapsed as a result of heavy rainfall during typhoon seasons. To mitigate the bridge damage caused by scouring, an improved warning system is required. Three fundamental parameters including the water level, the flow velocity, and the scouring depth (SD) are significant for the structural safety of a scoured bridge. Nowadays, these parameters can be successfully detected by advanced monitoring instruments and serve as a database for a damage assessment system to carry out the function of early warning. Therefore, this article aims at developing the damage assessment system for scoured bridges as the core of a warning system.

We have proposed an analytical process as an assessment system. Through finite element analysis with respect to water level and flow velocity, the critical scouring depth with a specific degree of safety factor for a bridge foundation can be determined by choosing among different failure modes. Accordingly, the relationships between various possible sets of water levels, flow velocities and critical SD are established to present the surfaces of structural safety corresponding to different levels of safety factor. The surfaces obtained can then be applied to the warning system.

Based on the proposed assessment process, the collapse of the Shuang-Yuan Bridge caused by Typhoon Morakot in 2009 is discussed in detail. The consequence of bridge collapse is reasonably explained by the analytical surfaces of structural safety based on the reported parameters at the bridge site. In addition, the Dia-Jia-Hsi Bridge, which has implemented advanced monitoring instruments serves as the second case study. The surfaces of structural safety obtained have been used in conjunction with real-time observations of sensitive parameters to display the situation of structural safety at any time. The results obtained in this article benefit bridge engineers, giving a safety-management platform to speed up the decision making process during an emergency.