Experimental study on seismic behavior of full-scale fully prefabricated steel frame: Members and joints

In a full-scale seismic test conducted by the present authors on a fully prefabricated steel frame, strains on the surfaces of beams, columns, braces and slabs were monitored, and the deformations in nine bolted end-plate joints were detected. The global responses of the frame and the composite action of the slabs were analyzed and discussed in the first companion paper. The seismic behavior of members and joints in the frame test were studied in-depth in this paper. Real boundary conditions of joints assisted more accurate study of the cyclic responses of end-plate joints compared with the general experiments on T-shape joints and cruciform joints. Seismic responses of flexible braces, beams and columns were analyzed. Hysteretic performance, backbone curves, the components of story drift ratios and energy dissipation of bolted end-plate joints were discussed. Based on these previous contents, the plastic development sequences and failure modes of the frames were summarized. The results indicate that satisfactory cyclic behavior, deformation capacity and energy dissipation were exhibited in members and joints. Over 65.3% of story drifts were induced by member bending in the elastic stage, but the increments of story drift were dominated by joint deformations after the 1.44% overall drift ratio loading stage, and the cumulative story drifts caused by joint rotations reached the proportions of 57.9-83.9% at the ultimate displacement. The maximum percentages of joint cumulative energy dissipation were 69.7%, 59.0%, 56.4% and 18.2% for the first, second, and third story and the whole specimen, respectively. The plastic development sequence and the failure mode of the frame were yielding of braces (0.36-0.72% overall drift ratio), yielding of end-plate joints (0.72-2.16%), yielding of column bases (1.80-2.16%), yielding of panel zones (≥1.80%), and yielding of several beam ends and column tops (≥4.32%).