Method for Identifying the Damping Coefficient from the Acceleration Measured During Earthquakes

This paper presents a method for identifying the damping coefficient during earthquakes in quasi-real time using the information from sensors installed in real structures. The method uses a given number of points to perform a quadratic regression in such a way as to reduce the error in identification. A coefficient of determination is also used to discard values that have not been correctly identified. The validity of the method is assessed by dynamic analysis in single-degree-of-freedom systems, using the initial stiffness proportional damping model and the tangent stiffness proportional damping model. Good identification results are obtained using a data acquisition sampling frequency of 200 Hz. The same is true for using a sampling frequency of 100 Hz as long as the system period is greater than 0.40 s. Additionally, it is observed that a 20% identification error does not substantially affect the seismic response of the system. The method is also applied to results from shake table tests, and their identified values are analyzed. A comparison is made between the behavior of the damping coefficient observed in the experimental tests with the behavior assumed in the dynamic analysis. In general terms, it is observed that the damping coefficient does not present abrupt changes in its values when changing the instantaneous stiffness as occurs in the tangent stiffness proportional damping model. Additional conclusions are presented that allow us to continue expanding the knowledge on the damping coefficient behavior during earthquakes.