Cyclic behavior of high-performance fiber-reinforced cementitious composite corner joints

Abstract

In moment frames, beam-column joints are critical elements that ensure the structural integrity of the frames. During earthquakes, beam-column joints can withstand large shear forces transmitted from nearby columns and beams. In old reinforced-concrete (RC) moment frame buildings, beam-column joints had little joint transverse reinforcement, which are susceptible to significant damage during large earthquakes. Their corner joints could experience a more severe seismic loading environment than other joints because they are subjected to bidirectional lateral loadings during earthquakes. The objective of this study was to improve the cyclic behavior of corner joints by using high-performance fiber-reinforced cementitious composite (HPFRCC). For this purpose, seven corner joint specimens were made and tested under unidirectional and bidirectional cyclic loadings. The application of HPFRCC improved the cyclic behavior of corner joint specimens. The contribution of HPFRCC outweighed that of the minimum joint transverse reinforcement. The minimum joint transverse reinforcement moderately affected the cyclic behavior of the specimens. The shear strength and drift capacity of unidirectional HPFRCC specimen without the joint transverse reinforcement had 13% and 24% larger than those of unidirectional RC specimens with the joint transverse reinforcement, respectively. Similar observations were made for bidirectional specimens. Particularly, the failure mode of the specimens was changed by using HPFRCC from brittle joint shear failure and axial failure to beam flexural failure followed by joint shear failure.