Open space damping system theory and experimental validation
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Seismic energy dissipation systems are typically installed in buildings within diagonal or chevron bracing to improve the seismic performance by reducing drift, and under certain conditions by reducing acceleration. Alternative installation methods have been developed in which novel mechanisms are utilized to magnify the displacements within the damping system and thus improve performance when drift is small and by doing so may also reduce the cost of damping. Examples are the lever-arm, the toggle-brace, the coupled-truss and the scissor-jack damper systems which have found a limited number of applications. All damping system installation methods visually and physically obstruct an otherwise accessible area within the bay of the frame to which they are installed. This drawback has resulted in the occasional rejection of use of damping systems by architects. This report introduces a novel configuration for damping devices with the main advantage of preserving open space within the frame of installation-hence the name “open space damping system”. The report introduces the concept, presents the theory and then presents computational models to verify the theory and to investigate the effects of frame configuration, frame deformations and large deformations on the effectiveness of the system. An experimental study of a large scale model with the open space damping system was conducted and used to acquire data for validating the developed analytical and computational models. Testing consisted of (a) a single portal frame tested under imposed lateral motion, and (b) a single story 32kip model tested on the shake table under seismic excitation. Two different configurations of the open space system (plus a third variant of one of the two) in three different structural system configurations were tested. The tests demonstrate the increase in damping provided by the damping system. Comparisons of experimental results in terms of structural drift, floor accelerations and force-displacement loops to results obtained by computational tools demonstrate the validity of the computational models.