Identification of Seismically-Induced Local Damage in Steel Moment-Resisting Frames Using Wireless Strain Sensing

Abstract eng:
Steel moment-resisting frames subjected to severe ground shaking may suffer local damage (e.g., fractures) at beam-column connections, which likely impair the safety for occupancy. Post-quake safety evaluation and decision-making for steel moment-resisting frames mainly depends on the inspection results of local damage to beam-column connections. This paper presents the comprehensive overview on the recent developments at DPRI, Kyoto University on a local damage evaluation method for identifying seismically-induced beam fractures in steel moment-resisting frames. A local damage estimator that consists of damage index, decoupling algorithm, and damage curve is developed for quantitatively identifying beam fractures. A damage index is formulated from a comparative study of the strain responses before and after earthquakes. Decoupling algorithm is necessary to estimate the damage index for each individual fracture under multiple damage condition where the damage indices for neighboring fractures correlate each other. The derivation of a damage curve enables to translate the decoupled damage index into the physical properties of fracture, i.e. the reduction of its bending stiffness. Finally, the effectiveness of the local damage evaluation method was experimentally examined using vibrational tests on a large-scale five-story steel frame testbed that was designed to accommodate seismic fractures at beam-ends.

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