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Precast columns

Precast concrete columns may be single or double storey height. The method of connection to the foundation and to the column above will vary with manufacturer. Foundation connection may be via a base plate connected to the column or by reinforcing bars projecting from the end of the column passing into sleeves that are subsequently filled with grout. Alternatively, a column may be set into a preformed hole in a foundation block and grouted into position.

Column-column connections may be by threaded rods joined with an appropriate connector; with concrete subsequently cast round to the dimensions of the cross-section of the column. Alternatively, bars in grouted sleeves, as described above, may be used. This results in a thin stitch between columns while the previous approach requires a deeper stitch. Connections may be located between floors, at a point of contra-flexure, or at floor level.

Columns are provided with necessary supports for the ends of the precast beams(corbels or cast-in steel sections). There will also be some form of connection to provide beam-column moment connection and continuity. For interior columns this may be by holes through which reinforcing bars pass from one beam to another. For edge columns, some form of bracket or socket is required.

During erection columns must be braced until stability is achieved by making the necessary connections to the beams and slabs.

Acknowledgement: The Concrete Society

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