Stylish new home of Tata Consultancy Services
`TCS House’ – originally the `Ralli House’ was built in 1922 and remodeled in 1966. `Somaya & Kalappa Consultants’ were appointed by `Tata Consultancy Services’ in 2005 when the latter bought the building for the purpose of converting it into their `Global Headquarters’.
The building was a load-bearing masonry structure with an internal framework of r.c.c and steel. However, it had detoriated considerably over the years and the external walls which were brick, faced with approximately 300 mm thick stone had delaminated. The slabs were distressed with exposed & scaling reinforcement. Mainly original beams were further reinforced with additional structural steel members. Accordingly, a decision was taken that “retrofitting and patch work strengthening” would not work in the long run & completely new r.c.c. framework & floor slabs needed to be erected.
The challenge of a structure totally covering the site in an urban setting was further compounded by the fact that the existing stone shell (3 sides) had to be retained as this building was classified as a Grade II-A heritage structure. To achieve this, key existing structural elements (columns & beams) were either left untouched or temporarily strengthened. Then the new r.c.c frame work was erected while simultaneously removing the earlier support system. Care was taken to ensure that at any given point in time the unsupported height of the stone walls was restricted to a maximum of 8 meters (height of two floors). Additional external supports in the form of standard “H” frames were introduced for additional bracing. However, the size of the frames needed to be restricted as they were erected on a public foot path.
The demolition of the existing beams and columns was carried out by a specialist contractor in a very phased and precise manner. Care had to be taken while dismantling that the vibrations caused by the cutting equipment were not transferred to the stone wall. Thus, the initial option of using the diamond chain saw to slice the beams was limited in favour of hand held chippers. The additional advantage being that the chippers could totally disintegrate the concrete member & facilitate easier removal of debris as there was absolutely no place to stack the cut structural members.
An additional complication was working in the heavy Mumbai monsoon rain with the stone walls propped and the high ground water table which required the constant use of dewatering pumps to enable work to go on.
The only minuscule open space on site was occupied by an existing electrical transformer which was supplying power to the adjoining buildings & had to be left untouched & functioning while the demolition & the re-erection work was going on. The south side structural glazing wall & cantilevered floating staircase could only be erected once this existing transformer was shut down & removed by the statuary authorities.
As the windows are high and the gap between the slab soffit & the window lintels is restricted, the floors are designed as flat slabs with post tensioning tendons using ready mix concrete.