Posterior Time‐Step Adjustment in Pseudodynamic Testing

Experimental errors are inevitable in pseudodynamic testing. Some of these errors can be monitored during the test, but, due to limitations in control system, they cannot be eliminated. For example, one cannot control exactly the displacements that are actually imposed on the structure at each time step. This paper focuses on a technique to minimize the cumulative effect of such control errors. For this purpose, a posterior adjustment of the time increment from a target value $\Delta t$ to an adjusted value $\Delta t_n$ is performed to minimize the effect of the control errors. The method is particularly for effective single‐degree‐of‐freedom systems and systematic errors. These systematic errors can have a very detrimental effect, and they are eliminated almost completely for the single‐degree‐of‐freedom example considered. For random errors that are probabilistically independent from one time step to the next, the method can have a deleterious effect on the error propagation characteristics, even though the control errors at each time step are reduced. However, since the effect of such random errors is small, this is not a serious draw‐back. For multi‐degree‐of‐freedom systems, posterior time step adjustment can also improve the error‐propagation characteristics for certain systematic errors but its effectiveness is more limited.