NEW SEISMIC TESTING METHOD - I - FUNDAMENTAL-CONCEPTS

A new hybrid testing method is presented, which is based on separating the ground motion components into two arbitrary additive parts. The s imulation of the first part is accomplished with a conventional shakin g table, whereas the second is carried out with actuators acting direc tly onto the structure. The concept is demonstrated here by means of a simple one-degree-of-freedom system, but a companion paper in this is sue shows that it is also valid for a system with many degrees of free dom, including those that exhibit material and! or geometric nonlinear ities. The hybrid strategy presented here could offer several advantag es in the design of a seismic testing device, particularly when the ac tion of multiple ground motion components must be considered simultane ously. Among the potential benefits one could cite: considerable reduc tions in the total power and energy requirements; substantial decrease in stroke and thrust of the actuators needed to move the table or exe rt forces on the structural masses; simplification of the support mech anisms needed to shore up the structure and resist overturning moments when vertical and rotational components are simulated; and the possib ility of using novel, low-frequency force actuators (such as jet engin es or unbalanced flywheels), which need not have the capacity of rapid ly changing the thrust.