A PRECAST CONCRETE FRAME SYSTEM FOR SEISMIC ZONE FOUR

A new precast concrete ductile moment resisting frame system, currently under development, is described. The proposed system is intended for medium rise office buildings, parking garages and other structures in regions of high seismicity. Lateral loads are resisted by the perimeter columns and spandrels. The precast reinforced columns are designed using the same requirements as for columns in a cast-in-place ductile frame. The system uses a specially designed precast spandrel to provide the energy-absorbing capability. The spandrel contains diagonal mild steel flat bars, debonded from the concrete, which may yield throughout their length in tension and compression. The precast concrete spandrel prevents buckling of the flat bar when it is yielding to compression. Connections to the column are made with special ductile iron castings that permit rapid field erection. The connections are designed to be sufficiently strong so that all yielding takes place in the mild steel flat bars, not in the connections. Component tests have been made and a full-scale test program is planned to verify the design concept. The appendix contains a design example of a portion of a building applying the principles developed in this paper.