90 thema Infosys multi level car park 1 Challenging Indian project in prefabricated and in-situ concrete Precast India IPL built the Multi-Level Car Park for their client, Infosys Ltd, in their Pune campus. This eye-catching, half a million square feet multi-level car park was used for the cover page of fib Bulletin 78 and was also named as 'The Outstanding Concrete Structure of India-2016' by Indian Concrete Institute (ICI). Special awards were also won in architectural, structural and precast construction categories. In total there were 3500 elements in the building of the Infosys multi level car park, consisting of: 16 m span precast TT slabs, 15 m precast concrete columns, and 1300 façade elements each around 7 m long and weighing 2.5 tons, triangular in profile, fixed in around 160 days on-site, with a self-designed and electronically managed factory and construction site coordina- tion, culminating in the installation of all elements within an erection tolerance limit of +/- 10 mm. With the steady rise in the Indian economy, the construction industry has become the second largest industry which contributes to the country's growth. This growth magnified demands for quick, clean and hassle free construction technologies and has thus laid 'concrete' foundations for the precast technology in India. An example of this trend is the Infosys multi level car park in Pune (photo 1). The challenging project is constructed fully in concrete, without any other materials, with the combination of prefabricated elements and in-situ concrete. thema Infosys multi level car park 3 2017 91 LIFT-1 LIFT-2 LIFT-3LIFT-4 LIFT-5 LIFT-6 The precast concrete elements in the building speak volumes about the innovations and the cutting edge technologies that were used for the construction of this magnificent structure. Concrete was chosen over glass, which resulted in excellent natural lighting and ventilation factors, minimizing future maintenance costs, and enhancing safety. International architectural design competition To meet the client's requirements, Precast India conducted an international design competition for the façade. From a number of designs, the entry from Arch Domingo Seminario was selected. The architecture of this structure is a perfect example of how uber modern structures can be designed to blend with the basic architectural concept evolved from and resembling the warmth of woven wool, with a virtue of unharmed air circulation along, with sufficient mild sun light entrainment in all the area. The parking structure comprises of a basement and ten floors with a parking capacity of around 1300 cars. In addition to precast concrete columns, beams, double tee slabs, hollow core slabs, staircases, and spandrels, the uniqueness of the building lies in its 1300 odd, 100 mm thick precast concrete façade elements (photo 4) [5], all of which were produced and trans- ported from Precast India's plant (photo 5) 45 km away from the site. This is a unique structure of its kind in India, where, instead of glass or aluminum composite panels, structural concrete prefabricated elements are used for the façade. Structural design The structure lies in seismic zone 3 [1] and was designed and analyzed by a team of experienced structural designers, led by prof. Sypros Tsoukantas and mr. Tryfon Topintzis. The struc- tural design of the precast elements [4] was complex as it involved intricate connections between prefabricated base- ment walls-columns/rafts, and floor to façade elements. The Er. Ajit Vasant Bhate Precast India Infrastructures Pvt Ltd 1 The Award winning façade elevation of the completed structure of the Infosys multi level car park 2 Typical architectural floor plan 3 The architectural design is inspired on a woolen weave pattern 4 The woolen weave concept elevation 3 4 2 Infosys multi level car park 3 2017 92 5 Precast India plant which made intricate prefab projects possible 6 Bare façade element (a) and a mock up façade-spandrel connection (b) 7 Spandrel element with dowels for connection to column corbel (a) and column sides (b) Integrated it systems A 3D Tekla model including all reinforcement and precast connections was made. Highly accurate production drawings were generated from this model and the production of the elements was carried out accordingly. Completely in-house developed, cloud based planning and tracking software, generated production and erection schedule along with sequence for installation and a full-fledged data base of elements. Other IT systems facilitated online booking of connections are ductile [3], sturdy and unyielding. Shear forces between spandrel and façade elements are transferred by the monolithic corbels in the spandrels which are also interlocking each façade element against overturning (photo 6). The ductility [3] of connection between the façade element and building spandrel was achieved by use of mild steel bolts to offer moment of resistance for 1.50 m cantilevering façade element. The use of mild steel bolts offers sufficient warning before failure in the seismic event. 5 6a 7b element connected to spandrel corbel monolithic with spandrel resisting shear spandrel element fixed on column corbel at base and knife plates on sides of either side columns niche in façade element bolt going through to other side of spandrel corbel monolithic with column having sleeves for spandrel dowels spandrel element fixed on column corbel at base and knife plates on sides of either side columns side connection with column to absorb torsion spandrel dowels fixed in column corbel 6b 7a thema Infosys multi level car park 3 2017 93 8 Three-storey column erection 9 Lifting frames (a) and stacking (b) of façade elements 10 One of the many innova- tions: the double decker transport system Stacking Long spans and critical geometry of elements (photos 9a and 9b) were a concern while stacking. A separate special support lifting system was designed to de-mould and stack the elements, avoiding lifting and handling stresses thereby lifting the façade elements delicately, but quickly. Transportation to site Transporting fragile elements 45 km through narrow and choked roads was a challenge, considering the road conditions, lifting and handling stresses. This prompted attention to resources (RMC, trailers, cranes), logistics management purchase orders, material management and budget tracking. Production and quality control systems Even the smallest details and activities were planned well in advance before production drawings were made and unique element IDs were generated to be able to pinpoint the life cycle stages of each individual element from design stage up to final installation on site. The state of art production facility, consisting of a hollow core slab unit, Carousel unit (for solid slabs, walls), mechanically and hydraulically operated adjustable beam and column moulds giving smooth surface finish, special batching plants, tilting tables, shear cut bend lines (steel cutting), gantry cranes, steam curing facilities, etc., produced all precast elements in the project, with a concrete grade of M40 MPa. All the risks and challenges like demoulding, lifting, installa- tion, anchoring etc. were eliminated and structurally approved by mockup tests. Sample prototypes were cast multiple times, and representative elements were tested till failure. Multiple tests on raw materials, load tests for representative elements were done and certified by third party testing agencies, before full scale production began. Each test and control greatly helped in achieving the high quality and consistency with regards to strength and finish, resulting in the good durability. 8 9b 10 corbel monolithic with column having sleeves for spandrel dowels knife plates for side connection with spandrel element 9a Infosys multi level car park 3 2017 94 11 Intermediate stage of façade installation, showing a corner column 12 Interior of the fully finished structure 13 Exterior of the fully finished structure Installation on site The entire erection of the 3500 elements was a pre-planned activity, even before the production planning, considering all the major constraints at site like restricted side margin availa- bility, limited access, availability of special tools and tackles etc. The installation of the odd façades was accomplished with an average erection time of 25 minutes per façade element. For installation of TT slabs, columns, beams and other elements of the structure, a 50MT rail mounted Liebherr tower crane was set up on rails in the center of the building, considering element weight and available crane capacity at the required radius (16 tons at 48 m). 50 ton and 120 ton mobile cranes were also used. Accuracy, tolerances and precisiom An overall accuracy up to 15 mm without any adjustment anywhere was achieved despite the complex nature of all the precast elements. The 20 mm bolts in the façade element passing through the spandrel sleeve of 40 mm, had overall tolerance of 20 mm only, including also other tolerances during erection of foundations, columns, beams etc. This came as a result of constant coordination and exchange between all the stakeholders [9] including design, planning, production, transportation and installation of all the elements. Finally, perfect coordination between all stakeholder teams, ensured the creation of milestone and a unique game changer in the Precast industry in India. ? ? REFERENCES 1 BIS, I. (2000). Indian Standard ( IS ), Plain and RC-Code of Practice. Bureau of Indian Standards. 2 Standard, I. (1893). Criteria for earthquake resistant design of structures. Indian Standards Institution, IS, 1975. 3 BIS, I. (1993). 13920 Ductile Detailing of Reinforced Concrete Structures subjected to Seismic Forces?Code of Practice. India: Bureau of Indian Standards. 4 PCI Design Handbook, Precast and Prestressed Concrete (1985). Chicago: Precast and Prestressed Concrete Institute. pp. 11-18. 5 BSI, B. S. 8110-1: 1997 Structural use of concrete?Part 1: Code of practice for design and construction. 6 Building code requirements for structural concrete (ACI 318-08) and commentary (2008). ACI Committee, & International Organization for Standardization. 7 Ajit V Bhate, Jt. MD, Bhate & Raje Construction Co. Pvt. Ltd and MD, Precast India Infrastructures Pvt. Ltd., 2010-present. 8 Precast India QAQC Manual, 2015. 9 Precast India MPFC (Meta Process Flow Chart) Document, 2015. the economical considerations and resulted in the decision to transport multiple elements simultaneously. The transportation experts innovated a double decker transport assembly system designed and fabricated as a removable attachment, ready to shift eight façade elements per trip (photo 10). This improved installation speed and enabled meeting the target dates. 11 12 13 thema Infosys multi level car park 3 2017