Seismic performance of RC-ECC composite frame by eliminating shear reinforcement in beam-column joint: Shake table tests

The inherent vulnerability of beam-column joints to seismic loading and steel congestion are two major research problems connected with beam-column joints of moment-resisting frames. The experimental study presented herein addresses these research questions and seeks to solve them by using Polyvinyl Alcohol based Engineered Cementitious Composite (PVA-ECC) in beam-column joints without transverse shear reinforcement. The study included the manufacture and shake table testing of two 1:3 reduced scale one bay two-story moment-resisting frame models using simulated earthquake motions. To evaluate the performance of ECC beam-column joints without shear reinforcement, two frame models, one with and the other without shear reinforcement in the beam-column joints, were prepared and tested. The acceleration time history record of the 1994 Northridge Earthquake USA was used for the excitation of specimens at different levels to produce progressive damage up to the near collapse state. The observed damage mechanism of tested models was recorded, and the response parameters, including floor displacement and acceleration, were measured. The measured data was processed to develop a lateral force-displacement envelope curve for the supposed prototype frames and calculate their seismic design factors (ductility, overstrength, and response modification). Comparison of the seismic performance parameters of the two prototype frames reveal that the ECC beam/column joint without shear ties performed marginally inferior to the ECC beam-column joints having shear ties but it still achieved a 75% larger R-factor compared with the code specified value.