PAPER 1(Summary)
A perspective on seismic design of Precast concrete structures in
New Zealand – Robert Park(PCI journal : 1995)
MOMENT RESISTING FRAMES WITH PRECAST REINFORCED ELEMENTS
The approach is to design and construct connections that possess stiffness, strength & ductility similar to that of cast-in-place concrete monolithic constructions
The three different types of beam column connection arrangement are discussed below: 1. System 1 * The precast beam elements are placed on the cover concrete of cast-in-place columns * The reinforcement is then placed on beam top, the beam-to-column joint core & next storey height column * Lastly, cast-in-place concrete is placed * A mechanical key may be provided at beam end to take care of the vertical shear.

Advantage * Large reduction in quantity of site formwork
Limitations
* Column dimension need to be reasonably large to accommodate the required development length of bottom reinforcement of the precast beams in joint core. * The critical section of the potential plastic hinge region in beam occurs at the column face where there is a vertical joint between the cast-in-place concrete of the joint core & end of the precast beam. 2. System 2
The precast portion of the reinforced concrete beams extend from near mid-span to mid-span and include within the precast element over the columns the complex arrangement of joint core hoop reinforcement which is fabricated at the pre-casting site itself.
The longitudinal reinforcement of the columns are passed through the preformed vertical holes at the joint core of the precast beams after which they are grouted.
The protruding bars of the beams are connected in a joint to be cast-in-place at the mid-span.
Advantage
* The potential plastic hinge region in beams occur within the precast elements away from the jointing faces between the precast elements * Makes extensive use of precast concrete and eliminates fabrication of complex reinforcing details during construction and placement of cast-in-place concrete in congested beam-column joint core.
Limitation
Tighter tolerance is necessary when assembling the precast elements.

Construction of a 22 storey building in New Zealand using system 2 3. System 3
Use of T-shaped precast reinforced concrete elements where the vertical column bars are connected using grouted steel sleeves or ducts & at mid-span of the beams the bars can be connected in cast in place concrete joints.
Alternatively cruciform shaped precast units with joints between columns occurring at mid-height of the stories can be used
Advantage
Makes extensive use of precast concrete and eliminates fabrication of complex reinforcing details during construction and placement of cast-in-place concrete in congested beam-column joint core
Limitation
The precast elements are too heavy and crane capacity may be an important consideration

Note: According to New Zealand concrete standard NZS 3101:1995 that lap splice of the longitudinal reinforcement of the precast beams should not lie within a length equal to the effective depth of the beam from the critical section of the potential plastic hinge region.