The RTRI developed the member angle monitoring unit for RC rigid frame viaduct column during seismicity with the aim of enhancing the accuracy of damage evaluation and reducing the downtime of operation line after the earthquake. This unit can measure the maximum response member angle in any direction of a viaduct column’s upper end using two-direction mechanical(i.e., power-source free) displacement peak sensor via a measurement bar, and estimate the damage level of the columns. It can also estimate the damage level of columns whose interior parts cannot be surveyed because of steel jacket reinforcements (Fig.1).

The RTRI confirmed that the difference between actual and measured member angles is equal to or less than 10% for a member angle of 0.01 radians or over that is sufficient to damage the columns. This was clarified through static tests with only member angle measurement unit, static loading tests with the unit set on a scale model column, and dynamic vibration tests with the unit set on a scale model column.

To apply the unit to operation lines, the RTRI developed an arrangement location selecting method to enable efficient estimation of damage levels of viaduct columns using limited numbers of member angle measurement unit. The RTRI conducted damage level analysis with earthquake motions on 4 model lines, and clarified that error margin of presumption algorithm within 10% if the devices are arranged at 500m intervals in consideration of the response characteristics of viaducts, for instance, with respect to near-land interpolate earthquake motion (Fig.3).