Ajit Vasant Bhate
MD, Precast India Infrastructures Pvt. Ltd.
The first glimpse that one gets of the 50 acre sprawling Infosys Pune campus is its eye-catching 4.5 lakh sq. ft multi level car park – one among the many challenging creations of Precast India Infrastructures Pvt Ltd.
The precast concrete facade which envelops the building speaks volumes about the innovations and the cutting edge technologies that have been used for the construction of this imposing structure, after many considerations of sustainability which resulted in excellent natural lighting and ventilation factors.
This is almost the first of its kind in India, where the structural concrete prefabrication industry is yet to gather momentum, and the use of glass or ACP is rampant and considered as the only material for external cladding of facades. Therefore the execution of this project at the nascent stage of birth of Precast India Infrastructures Pvt. Ltd. was definitely a huge challenge successfully met.
The facility comprises of a basement and ten floors, catering to a parking capacity of around 1300 cars. It is constructed with the combination of cast in situ concrete shear walls (around 20% volume), prefabricated structural elements basement walls, columns, TT slabs, spandrels, hollowcore slabs, staircases, etc. and later on wrapped fully with precast concrete facade elements, which were produced and transported from Precast India Infrastructures Pvt. Ltd. factory 45 km away from building site.
The subject matter of this particular article deals only with the challenging issue of the façade, (which is separated from the construction of the precast parking structure).
The confirmation for the façade per was received during construction of the foundations, and therefore quick action on structural redesign was necessary. Precast India Infrastructures Pvt. Ltd. organized an International Architectural Competition including nominating seven prestigious International and National Architects having expertise in prefabricated concrete. Within 45 days the winning entry was selected by the Client and signed off by the Hon. Shri Narayan Murthy of Infosys for execution.
Architectural Design and concept of Façade elements
The Architectural conception resembles a woollen weave, sustainably enhancing the motive of maintaining sufficient mild sunlight in the maximum area and protection of unharmed air circulation by elegant design of facade. The uniqueness of the facade element also lies in its lean 100mm thickness and the ability to robustly envelope the whole structure for 10 floors.
Structural Design of Façade elements
The unique structural design for connection of the column and the spandrel, the façade element and spandrel, and façade element to façade element was achieved after at least ten different conceptions, permutations and combinations, and is a separate issue requiring detailed description.
In brief the challenges and constraints of this project explained in terms of production, stacking, transportation and installation are as below.
Post successful preparation of the elevations in design and drawing office, Unique ID’s were generated for all elements to streamline the production process, i.e. mould allotment, and quicken the production process. The entire procedure was tracked and controlled electronically using specially developed software ERP systems, automatically connecting the Architectural design and Structural drawings in 3D formats, preparation of production drawings, the actual production process, quality controls with requisite record submittals to the Client, transporting, stacking locations, tracking during installation etc, all connected and weaved through a uniquely self-designed electronic format, knowing the strong and weak points of the internal execution system.
The production of sample prototypes were done till all challenges like high demoulding time of 24hrs, formation of air bubbles probable, cracking in shear zone and cracking at lifting hooks were completely eliminated and approved structurally. After this approval, around 1300 elements were casted in our plant in just 90 days or so,
Post production, stocking the element was a concern because of the critical geometry of the facade element. For avoiding lifting and handling stresses, a separate special support lifting system was designed in-house to stack the elements effectively, and quickly.
Transportation to Site
Transport of these elements on existing roads was a definite challenge considering the delicate and fragile elements, the lifting and handling stresses etc. There also was the question of economics in transporting single or multiple elements 7 odd meter long and 2m wide elements.
Therefore, transportation experts at PIIPL developed a saddle system which not only carried the facade elements safely but also enhanced the transportation efficiency to a large extent. In this way, the installation speed was also improved to meet the target dates. Double decker transport assembly which transported upto 8 Facades in one trip was designed and fabricated as a removable attachment to the trailers.
Installation on site:
Entire erection of the facade elements was a perfectly pre-planned activity. The restricted side margin availability, limited access to the site, availability of special tools and tackles for facade erection were the main constraints. Facade erection was a very challenging task and setting up the mobile cranes according to the required positions and boom angles was achieved seamlessly.
The installation of facades at the Multi-Level Car Parking Project was propitiously accomplished by erecting 1300 facade elements with an average erection time of 25min per façade element. Pre-planning and co-ordination had resolved many issues at the site especially due to restricted space availability, limited site access and space for stacking. Regular brainstorming on predicaments and implementation of resolving techniques like quality checklist at every stage for quality tracking helped in faster completion of project ensuring structural safety of facades.
Accuracy, Tolerances and Precision
Accuracy was a major element which was achieved though constant coordination and exchanges between all the stakeholders including design, production, transportation and installation of all the façade elements. The overall accuracy was maintained in a matter of 15mm, without any adjustment at any location, and this achievement was specially considered while all the various awards were announced for this project.
With all teams working in perfect harmony the successful completion of this project is really a milestone in the construction field and a game changer for the Precast Indian Industry.