Development and numerical simulation of hybrid effective force testing method

Effective force testing is a force-based experimental technique that can be used to simulate seismic response of lumped-mass structural systems. To generate the proper inertial force in an effective force test, the full structural mass has to be present in the test structure. The primary objectives of this research program are to develop an effective force test method with a virtual mass and extend it to incorporate the substructure technique to reduce the mass and structural components required in the test structure, develop a numerical simulation technique to enable a pre-test validation of the method, and investigate the actuator delay compensation methods when the virtual mass and the substructure technique is utilized in the effective force testing method.; A discrete transfer function approach based on control theory is developed and used throughout the dissertation. For the stability analysis of the developed force testing method, the relationship established between the integration algorithm and the discrete transfer function is applied to investigate the stability of the selected integration algorithms for nonlinear structural dynamics. The HHT alpha-method with a fixed number of substep iterations used in real-time pseudodynamic testing is also investigated using the developed discrete transfer function approach.; A virtual mass method is developed to include an analytical mass for the effective force testing method in the test structure. Two techniques are proposed to update the force command required for the servo-hydraulic actuator. The stability and accuracy of the two techniques are investigated using the discrete transfer function approach. The virtual mass method is then extended to incorporate the substructure technique to develop the hybrid effective force testing method. Numerical simulation using linear and nonlinear SDOF structures indicates good accuracy for the virtual mass method and the hybrid effective force testing method when compared with the exact solution.; To achieve good control of the actuator used in real-time testing, good servo-hydraulic system modeling is required. A simplified modeling using a first order discrete transfer function is developed for displacement control. Numerical simulation using the simplified model shows good agreement with experimental results. Using the developed model from the servo-hydraulic system identification, the proposed simplified modeling is then applied to real-time structural testing under force control.; To minimize the effect of actuator delay for effective force testing method with virtual mass and the substructure technique, commonly used compensation methods for real-time pseudodynamic testing and a new compensation method based on the proposed simplified modeling for the servo-hydraulic system are analyzed using the discrete transfer function approach. The frequency response characteristics of the equivalent discrete transfer function are shown to provide useful information related to the performance of various compensation methods. Compensation methods for the force-based real-time testing with virtual mass and substructure technique are discussed.