DETECTION OF NONLINEAR BEHAVIOR IN EXPOSED-TYPE COLUMN BASES USING THE SECOND TIME DERIVATIVE OF ABSOLUTE ACCELERATION

摘要

This paper proposes a method to detect damage due to change in the stiffness of dynamically loaded exposed-type steel column bases utilizing the second derivative of the absolute acceleration, called "snap". The column bases are designed so that either the anchor-bolt or the base-plate initially yields, resulting in a slip-type of restoring force response. The results show that it is possible to detect the nonlinearity due to change in stiffness by comparing a threshold value with the snap time history. This method succeeded the detect the anchor-bolt yielding at a high rate of 86%, however, the rate of the detection of the base-plate yielding was only 64%. This is because the stiffness change when the baseplate yielding occurs is more gradual than the case of anchor-bolt yielding, which makes the detection by "snap" difficult.