Bidirectional Pseudodynamic Testing

An implementation for the pseudodynamic testing of a one-story frame subject to bidirectional loading was proposed and its feasibility was experimentally verified. Three generalized degrees of freedom at the center of mass of the roof diaphragm are often used in formulating the equations of motion for the one-story frame in a nonplanar test. In this work, three loading points of actuators oriented in the original directions of these actuators were selected to formulate equations of motion. Since loading-point degrees of freedom instead of generalized degrees of freedom were used for a pseudodynamic test there is no need to construct the transformation between these two coordinate systems. Thus, there is no error propagation regarding these transformations. External displacement transducers were applied to measure the displacement components along the original directions of the actuators although the directions of these actuators may vary after the specimen deforms. This displacement measurement is easy to implement and saves a large space in the test setup. A series of pseudodynamic tests were performed and the responses were compared to shaking table tests. These test results attested to that a bidirectional pseudodynamic test can be conducted using the loading-point degrees of freedom and this technique is applicable to the three-dimensional testing of structures under multiple components of earthquake ground motion.