Quantification of seismic damage in steel beam-column connection using PVDF strain sensors and model-updating technique

Abstract

This paper presents an experimental verification of a method of evaluating local damage in steel beam-column connections using modal vibratory characteristics under ambient vibrations. First, a unique testing method is proposed to provide a vibration-test environment which enables measurements of modal vibration characteristics of steel beamcolumn connection as damage proceeds. In the testing method, a specimen of structural component is installed in a resonance frame that supports large fictitious mass and the resonance frequency of the entire system is set as the natural frequency of a mid-rise steel building. The specimen is damaged quasi-statically, and resonance vibration tests are conducted with a modal shaker. The proposed method enables evaluation of realistic damage in structural components without constructing a large specimen of an entire structural system. The transition of the neutral axis and the reduction of the root mean square (RMS) of dynamic strain response are tracked in order to quantify damage in floor slabs and steel beams, respectively. Two specimens of steel beam-column connection with or without floor slab were tested to investigate sensitivity of the damage-related features to loss of floor composite action and fractures in steel beams. In the end, by updating numerical models of the specimens using the identified damage-related features, seismic capacities of damaged specimens were estimated.