The impact of using hybrid polyvinyl alcohol-steel fibre ECC on the seismic behaviour of precast beam-to-column joints

The precast concrete (PC) beam-to-column joints are the main components that influence the seismic performance of PC joints. Many of the PC buildings have collapsed in past earthquakes due to the poor beam-to-column joints. Therefore, this research presents a study that utilises the new hybrid PC beam-to-column joints cast using ECC with a 1.75 % volume fraction of hybrid fibre consisting of 1 % polyvinyl alcohol (PVA) and 0.75 % hookedend steel (HES) fibres. Three samples, including one monolithic joint, were tested under a quasi-static-cyclic loading to assess the seismic behaviour of the joints. The hybrid joints were prepared using steel connection details with and without embedded steel plates in the PC beam. The test results demonstrated that the use of ECC for casting the hybrid joints and the adjacent beam areas can prevent brittle failure due to the superior mechanical properties of ECC. The hybrid joints have superior seismic performance in terms of load-displacement capacity, ductility, strength, energy dissipation, and failure mode compared to the monolithic joint. The beam ductile failure of the hybrid joints was observed due to the use of ECC-hybrid fibres; consequently, the shear failure was avoided. Therefore, the hybrid PC beam-to-column joints of this research are feasible to implement in active seismic areas.