Experimental Error Effects in Pseudodynamic Testing

The pseudodynamic test method is a hybrid, computer‐controlled, experimental technique that adopts a step‐by‐step integration procedure to analyze the seismic behavior of structures. Since the response of the structural specimen in each step of a test is evaluated with the experimental data obtained in the previous step or steps, experimental errors introduced in each step are accumulated in the numerical procedure. The error‐propagation characteristics of several integration algorithms that are currently used for such tests are examined. Mathematical equations that characterize the cumulative growth of experimental errors are formulated, and used to evaluate the error‐amplification effects of the algorithms. It is shown that the magnitude of cumulative errors depends on the numerical properties of the algorithm, the frequency characteristics of the specimen, and the nature of experimental errors. Moreover, it is found that numerically computed displacements should be used instead of experimentally measured displacements in the step‐by‐step computations.