A hybrid pseudodynamic testing platform for structural engineering research: Application for the development of an innovative retrofit scheme

The objective of this study is to develop an integrated hybrid Pseudodynamic (PSD) testing platform that can be utilized to evaluate the behavior of subassemblies, building, bridges, and various infrastructures under earthquake, dynamic or static loads, avoiding some of the problems associated with shake table tests or pure computer modeling methods. Explicit and implicit algorithms that have been employed or proposed by other researchers in PSD testing are reviewed and evaluated in this study in terms of their numerical stability, accuracy, and error-propagation characteristics. The improved alpha-method is employed in the current testing platform owing to its characteristics of unconditional stability, sufficient accuracy, and having been verified experimentally.; A pre-testing simulation computer program is developed in this study. In this pretesting simulation program, the restoring force of the virtual experimental substructure is calculated using ABAQUS instead of reading the value from physical tests. The pretesting simulations for six representative cases were performed, showing that simulation results were consistent with the analytical solutions obtained through the finite element analysis program ABAQUS.; The current testing platform is developed in an object-oriented C++ framework architecture. The entire testing platform was verified experimentally by performing a series of physical tests of SDOF and MDOF systems. Two computers were used in the tests of MDOF systems. The two computers were used to control the physical test of the experimental specimen, and numerical modeling of the analytical substructure. A solution for data exchange between the two computers was developed and was verified experimentally. A series of PSD tests were performed to investigate the effects of the convergence tolerance, initial elastic stiffness, and selection of reduction factor. The test results indicate that the effects due to these parameters are related to the input excitation energy. The larger the input energy is, the smaller are such effects. A start-restart procedure is embedded in the current testing platform to handle unexpected situations that could occur during tests.; A 3-story special concentrically braced frame was tested utilizing the PSD testing platform developed in this study. The current testing platform was further verified experimentally by performing the PSD testing of a realistic building with special buckling-enhanced braces developed as part of this study. The special buckling-enhanced brace consists of an inner core steel double angle and outer pipes strapped to the angle with industrial steel straps. The braces in the first story of the building were tested physically while the rest of the building was modeled using ABAQUS. The buckling capacity of the special buckling-enhanced braces was found to be nearly 33% larger than that of standard double angle braces.