Seismic behavior of concrete filled tube column-wide flange beam frames

Analytical and experimental studies on the seismic behavior of a steel moment resisting frame (MRF) with concrete filled steel tubular (CFT) columns were conducted. A prototype building was designed using current seismic provisions and recommendations from previous related research, where MRFs with CFT columns (CFT-MRF) constituted the main lateral load resisting system. The expected performance of the building was related to three seismic hazard levels, namely, the maximum considered earthquake (MCE) level, having a 2% probability of exceedance in 50 years, the design basis earthquake (DBE) level, defined as two-thirds of the MCE, and the frequently occurring earthquake (FOE) level, having a 50% probability of exceedance in 50 years. The building was expected to remain undamaged for FOE level earthquakes, have repairable damage and not exhibit strength degradation for DBE level earthquakes, and avoid collapse for MCE level earthquakes. An analytical model for CFT-MRFs was developed and used to evaluate the prototype building performance. The model accounted for material nonlinearities, including yielding and local buckling of steel and concrete cracking and crushing, as well as geometric nonlinearities, including the effect of the interior gravity frames. Static pushover and time-history analyses were conducted using the prototype building model to study the response of the building when subjected to ground acceleration records representing the DBE and MCE levels. The results of the analyses showed that the building satisfied the performance objectives.; The experimental phase consisted on subjecting a test structure representative of the prototype building to simulated earthquake excitations corresponding to the three seismic hazard levels. The test structure performed in accordance with the performance objectives, confirming the conclusions drawn from the results of the analytical studies. The experimental results were also used to calibrate the analytical model. The calibration studies showed that the analytical model provides a reasonable representation of the test structure response.; Based on the results from the analytical and experimental studies, CFT-MRFs can be successfully applied to seismic resistant design and their behavior can be studied using the analytical model developed in this study.