APPLICATION OF EQUIVALENT FORCE CONTROL METHOD FOR REAL-TIME SUBSTRUCTURE TESTING

摘要

The equivalent force control (EFC) method replaces the numerical iteration with a force feedback control loop for solving the nonlinear equation of motion in a real-time substructure test (RST) using implicit time integration algorithm. The accuracy and effectiveness of the method have been demonstrated with numerical simulation of linear single-degree-of-freedom (SDOF) structures,and validated with actual tests of an SDOF structure in which a damper was used as the experimental substructure. In this paper, the applications of the EFC method arc described for the actual tests of SDOF structures with spring specimen and bulckling-restrained braces specimen, and a multi-degree-of-freedom (MDOF) offshore platform structure with damper specimen. The effectiveness of RSTing with the EFC method has been validated with the tests. The SDOF tests show that the EFC method may exhibit excellent performance if the equivalent force controller is properly designed, even when challenged by the test of undamped structure. For comparison, the central difference method (CDM) with conventional displacement control was also considered in the MDOF tests. The MDOF tests validate the stability and accuracy of the EFC method and show that unconditionally stable implicit method with EFC is more suitable than the CDM for the tests of MDOF structures.