Ductile beam-column conneections in precast concrete moment resisting frames

Abstract

Post-earthquake field investigations on precast concrete structures revealed that thelevel of damage and the poor performance of the buildings during the 1999 Kocaeli and Düzce Earthquakes in Turkey were closely related to the performance of the precastconnections. As a result, a two-phase research program on the performance of precastductile beam-column connections was developed as a PhD Thesis.In Phase I, four different types of ductile moment resisting precast frame connections and one counterpart monolithic specimen, designed for high seismic zones, were tested.Precast specimens of Phase I may be subdivided into three subgroups as cast-in-place,composite with welding and bolted connections. Comparisons on the performanceparameters, such as energy dissipation and comparisons on ease of fabrication and economy reveals that the modified bolted connection of Phase I may well be used in highseismic zones.In Phase II, five hybrid connections with unbonded prestressing tendon and partiallybonded mild steel were tested. The main variable in Phase II specimens was the percentcontribution of mild steel to the flexural moment capacity of the connection. Each hybrid connection was compared with the monolithic reference subassembly in terms ofconnection strength, stiffness degradation, energy dissipation and permanent displacement.It is observed that the design philosophy of hybrid connections is satisfied when the mild steel moment contribution of the connection is around 30 per cent.Furthermore, a numerical model was developed for Phase II specimens to highlightthe hysteretic behavior under seismic loading.