The project is a Data Centre Building located in Mumbai, which is comprising of G+6 floors and 2 basements with total P-T floor area of about 35,000 sq. ft. Slabs were designed for 2 hour fire rating but fire continued for 5 hours.
The slab area of Ground Floor was severely affected by fire at Basement. The affected area was required to be repaired and restored with the same slab thickness as before within a strict timeline.
PTSI team was approached to assess the effect of fire. The affected slab area was identified as it was necessary to neutralise P-T force in that portion. Re-shoring was provided for surrounding slab near fire affected area and then concrete of identified area was removed. After installing anchorage and additional reinforcement, pouring of concrete in the anchorage area of unaffected part was done. Cables of unaffected area were stressed again to attain defined pre-stressing force. To generate continuity effect between existing and to-be-cast area, existing reinforcement of slab was kept intact.
Later, regular process was followed for the Post-Tensioned slab in affected area which was around 1060 sq.ft. (i.e. after preparing formwork, non-pre-stressed reinforcement was laid, cable installation and pouring was done). After achieving pre-decided strength of the new concrete, cables were stressed. All these process was completed in a record time of 25 days.
This slab was designed and executed using Unbonded Mono-strand PT System. Such easier solution may not be there in case of other P-T systemS as force neutralization process is difficult to achieve for such requirements.