MEASUREMENT OF DYNAMIC RELATIVE DISPLACEMENTS

A method for measuring relative displacements on structures subjected to simulated seismic-base excitations is presented. This method uses a group of strain gages, mounted end-to-end and wired in series, as the sensor. Because the sensors are mounted directly to the structure, problems associated with the motion of the mounting hardware are avoided. Prior to their use in dynamic applications, static tests were performed to verify that strain-gage sensors give relative displacement readings that are as accurate as those obtained with conventional displacement transducers. These tests also showed that the hysteresis loops measured with the strain-gage sensors were smaller than those measured with the conventional displacement transducers. At similar load levels, the relative displacement results measured during dynamic tests were similar to those measured during static tests.