Seismic design and hybrid simulation test of existing concrete frames upgraded by metallic damper

Abstract

Concrete frame makes up a large amount of current building structures. Therefore, there is a high need to upgrade the existing frame owing to material aging, cracking and crushing of concrete which significantly decreased the anti-seismic capacity. In this paper, the metallic damper was employed to upgrade the existing concrete frames. An interactive seismic design process was described to properly determine the yield strength of metallic damper of each floor. Two prototype buildings including one existing concrete frame and one existing concrete frame upgraded by metallic damper were selected as research objects. Hybrid simulation tests were performed to observe the seismic performance of prototype buildings, in which the numerical model was established by OpenSEES software and its accuracy was validated against the test results. The side span in the first story of the prototype building was selected as physical substructure. Based on the test results, it indicated that the metallic damper could significantly decrease the story drift of structure and relatively minor damage was detected on the metallic damper upgraded concrete frame compared with pure concrete frame. Typical failure modes and dynamic responses of two substructures were evaluated and discussed. Afterwards, the global responses of two prototype buildings were analyzed to reveal the influence of metallic damper. It suggested that the strength of metallic damper should be 0.4 to 0.6 times the story shear for better decreasing the story drift ratio and dissipating the input seismic energy. The test and analytical results provided a reasonable upgrade method for existing concrete frame under seismic actions.