Section, Member and System Level Analyses for Precast Concrete Hybrid Frames
Experimental studies have shown that precast concrete hybrid frames with dry jointed moment connections can provide adequate lateral force resistance for buildings located in high seismic zones. This framing concept, which has been approved for use by code officials, utilizes unbonded post-tensioning and mild steel reinforcement that is debonded over a short distance to establish a moment resisting connection between a precast beam and a precast column. As a result, the hybrid frames have the ability to dissipate energy and sustain minimal residual displacements when subjected to earthquake lateral forces. Due to the use of unbonded steel reinforcement, the hybrid connection concept introduces strain incompatibility between the reinforcement and the surrounding concrete, making the analysis and design of the connection difficult. Consequently, the available analysis and design methods for hybrid frame connections are based on many simplified assumptions.