Postearthquake Strength Assessment of Steel Moment-Resisting Frame with Multiple Beam-Column Fractures Using Local Monitoring Data

Abstract

Quantitative reports on postearthquake infrastructure condition are valuable to engineers, building owners, local government entities, and the public. Despite their utility, sensor-based protocols have not been widely embraced, primarily due to a lack of proper demonstrations. This paper introduces a methodology for determining the postearthquake strength of a steel moment-resisting frame with multiple beam-column fractures based on local monitoring data. The damage index (DI), an existing metric based on dynamic strain measurements, is applied to quantify damage-induced reductions in bending stiffness at each beam end in the frame with decoupling damage interaction effects. An analytical model with updated local stiffness information enables the estimation of the building’s reduced strength. The proposed methodology may be automated to provide crucial structural information that can optimize and supplement visual inspections immediately after an earthquake so that emergency plans may be initiated promptly. The methodology is first validated using experimental observations and sensor data collected during a substructure test. Then its application to strength reduction estimation of multistory, multibay frames is examined with shake table tests on a large-scale three-story steel frame. Fractures at beam-column connections are perfectly tracked in all damage stages using DI. Estimated reductions in base shear and stiffness are among the results produced, which permit explicit comparisons to performance design limits. Appropriate FEMA connection damage index values are included in the discussions.