IS-4326; 1993 has given recommendations regarding strengthening measures for precast roofing techniques. The code recommends that for building category A, B and C based on seismic co-efficient, a tie beam is to be provided all round the floor or roof to bind together all the precast components to make it a diaphragm. The beams shall be to the full width of supporting wall less the bearing of precast components. The depth of the beam shall be equal to the depth of the precast components plus the thickness of structural deck concrete, whenever used over the components. Tie beams shall be provided on all longitudinal and cross walls.
In category D, structural deck concrete of 35 mm thickness reinforced with 6 mm dia bars, 150 mm both ways and anchored into tie beams shall be provided. For economy, the deck concrete itself can serve as floor finish.
