Seismic Performance of Beam-Column Sub-Assemblies of a Demountable Precast Concrete Frame Building

Abstract eng:
Structural elements in conventional frame buildings are connected using “wet joints” (i.e. cast in-situ joints) to emulate the behaviour of a monolithic reinforced concrete (RC) frame building in transfer of loads to the foundation. Because of cast insitu joints, the inherent advantage of precast building over RC building in-terms of speed of construction is limited due to the requirement of formwork and curing time to erect other precast elements. Also, because of wet joints the structural system of a conventional precast concrete building is either fully or partially monolithic in form, which requires these buildings to be demolished instead of dismantling and reuse of undamaged components. Buildings damaged to a reparable state after an earthquake require considerable downtime to repair in addition to the cost to restore its functionality. This will induce substantial seismic losses contributed by direct repair cost, and more significantly by the downtime (i.e. occupancy interruption). Also, there is limited research work carried out in the development of fully “dry and rigid (i.e. momentresisting)” beam column connections for a precast concrete frame building. For these reasons, the authors are working on a frame building system using standard precast concrete elements and dry connections, which is quick to construct and easy to demount. The proposed building system can also be considered as a low downtime building system because of quick repair/replacement of damaged components (mostly lateral load resisting elements); thereby minimizing the seismic losses due to occupancy interruption. In this paper, details of different steel angle connection configurations between precast concrete beams and columns which make the overall building structural system demountable are reported. The philosophy in load transfer mechanism between the beam and the column is also explained. The effect of the variable parameters of the connection like beam edge distance, fill material between the connection and the precast concrete elements, condition of ducts on the beam side (i.e. grouted or un-grouted), and bolt configuration on the column side on seismic performance of beam-column sub-assemblies is investigated. The sequence of observed modes of failure in the beam with increasing lateral drift is reported. Based on the investigated parameters, the best demountable steel angle connection configuration that emulates the structural performance of the monolithic RC frame is identified and recommended for implementation.

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