1. A technique to extract scouring-apprehended bridge piers

  • Preparation of two scoring books for use in extracting scouring-apprehended bridge piers
  • The scoring table applicable to general inspection assumes visual inspection without requiring high-level expertise
  • The scoring table used for individual inspection evaluates the stability of bridge pier foundations into the future

To prevent scouring-related damage in flood condition, bridge pier structures are inspected to judge whether repair or remolding is required. For this purpose, scouring-apprehended bridge piers are selected by engineers in the field, meaning that not all candidate piers are necessarily extracted. This requires the establishment of a technique to extract scouring-apprehended bridge piers correctly and efficiently.

Accordingly, the RTRI has created two scoring tables as a means of selecting bridge piers for repair or remodeling. One is for primary extraction used in general inspection (Table 1) and the other is for secondary extraction in detailed inspection of individual bridge piers extracted in the general inspection. The RTRI has also prepared an application manual in relation to the tables. In general inspection, bridge piers are evaluated in 10 categories including river/structure conditions mainly through visual inspection based on the scoring table, without relying on high-level expertise on rivers. Those scoring less than 110 points according to judgment by expert engineers are classified as being susceptible to scouring damage (Fig. 1). In detailed inspection of the damage-apprehended bridge piers extracted in general inspection, scouring and riverbed degradationing speeds are estimated based on detailed information relating to bridge structure/river conditions and deluge history (Table 2). Through this process, the stability of bridge pier foundations is evaluated into the future.

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