Abstract
This paper presents a method of evaluating local damage in steel beam-column connections using dynamic strain responses measured under ambient vibrations. In the proposed method, inner-force distribution in steel beam-column connection was estimated using the natural modal components measured by PolyVinylidene DiFluoride (PVDF) strain sensors. For evaluating damage in steel beam-column connections, two kinds of damage-related features were proposed. One was the transition of the neutral axis for evaluating the loss of composite action between steel beams and concrete floor slab. The other was the reduction of the dynamic strain responses from the undamaged condition in terms of root mean square (RMS) for quantifying steel beam fractures. A unique testing method was developed to verify the damage-related features at component-level. In the test configuration, the specimen was damaged quasi-statically, and vibration tests were conducted as damage proceeds. Moreover, an analysis model of the specimen was built and updated using dynamic strain responses. This model-updating was particularly interested as it provided estimates on the residual seismic capacities of the specimens in terms of the quantities familiar to structural engineers (i.e., stiffness and strength).
