Building 7A, Gurgaon

The elevation of the building has been conceptualized to make it look like a “TELEVISION.” The front face of the building is elevated by 7 meters above the ground level and is supported over flared columns protruding out from the ground floor. The building also has three basements to accommodate the parking and services.

Built up Area: 0.487 million Sft
Project Cost: Rs. 56.78 Crores exclusive of Finishes.

Building 7A is one of the technically challenging building projects consisting of some special and demanding architectural features like flared columns, curved wall, etc., executed by DLF Laing O’ Rourke (India) Ltd.

Structure

The building has 9 clusters of flared columns. Each cluster is having a set of 4 columns totaling to 36 no’s of flared columns. This cluster of columns are protruding out from ground floor column of size 1200 x 1200 with a pedestal on top of it and merging into second floor level (height 7.60m) in diagonally opposite directions. These columns are inclined at an angle of 56.43 degree to the horizontal.

A transfer beam of 2800mm wide x 1100 mm deep has been provided at second floor level and these flared columns are terminated into it.

The methodology of casting of this column demanded that the column is to be cast in three pours as indicated in the view.

The Formwork for pour 2 was especially challenging and had to be of the shape as shown.

Description of Formwork

The C/S of Formwork used is as shown in the sketch above.

It comprises of FRP panels (two halves in plan) each 1.80m long.

The panels are bolted with each other using 150mm wide MS collars.

These collars are used for alignment of the panels and also to withstand the concrete pressure.

The collars are supported by struts and also by internal ties using wire ropes and turn buckles.

The starter and end pieces are custom built panels suitable only for the project whereas the rest of the component can be used on any project as formwork for 900mm dia circular column.

Methodology for casting the flared column

Stage 1

Reinforcement is tied to the full height of the column

The starter bars are placed and the ring portion connecting all the four columns at the bottom is cast (approx height–770mm).

Stage 2

The formwork for the rest of columns are bolted into position and aligned by using the struts as shown in the sketch 3. The collars are tied horizontally using wire ropes with turn buckles.

As can be observed from the sketch 2, the bottom most portion of the form work has eccentricity in terms of dimensions with respect to each side. Hence, it is decided to cast this portion first, and allow for the hardening time, such that the concrete in the higher portion will not exert force on the bottom most form work, but instead on the hardened concrete.

Concrete of the columns are done from the top by using Self Compacting Concrete.

Stage 3

The formwork for the rest of the column height is then placed duly connecting to the bottom portion of Form work and hardened concrete in addition to the collars and struts in position, and rest of the SCC is poured into it.

Productivity The productivity achieved on this project was 8 days with 15 people for the first cluster and gradually improved to 3 days and finally to 17 hours with 15 people for the ninth cluster. Self compacting concrete was the need of the hour. The mix is designed in house and used for the flared columns, which has solved the problem of concreting without the need for vibration.

Details:

The project involved the following, viz.,

24,714 cum of concrete
3,068 MT of steel
81,227 Sqm of shuttering
3,500 cum of brickwork
31,305 Sqm of internal plaster
4,863 Sqm of external plaster
Time to build: 24 months
38,212 Sqm of IPS
Value: Rs 56.78 crores

Curved Slab & Curved Wall

Another feature of this building is the curved RCC slab and wall along the length of the shorter span of the building i.e. bottom curved slab at second floor and top curve (terminating) at terrace level to get the Television effect. Some of the features of curved wall are as follows

Bottom curve has an arc from a circle of diameter of 5300mm and the arc length is 3600 mm.

The thickness of this curve at bottom point (i.e. start of bottom curve) is 500 mm and it tapers to reduce to 200mm (at end of bottom curve).

Top curve (i.e. at terrace) has an arc from a circle of diameter of 8400 mm with an arc length of 6200 mm and this has a constant thickness of 180 mm.

The form work for this is made up of steel members fabricated to suit to the curve as primary members. Ply and Timber sections are used as secondary bearer system, to suit to the curved shape. Concrete pouring is controlled in a meticulous manner such that the profile is achieved without the need for plastering.

Achievements

• Despite having challenging features like flared columns and curved slabs, etc, the site team has left no stone unturned to maintain the pace of progress and achieved an average of 12 day cycle time per slab for tower area including concreting of columns, core walls and stairs etc.
• At peak time, the team has achieved around 2900 cum of concrete (RCC) per month as against the available front of only 1200 cum per plate area (inclusive of verticals).
• Finally, all the hard work paid off and entire structure including the flared columns and curved wall were completed successfully well in time.

The productivity achievements are monitored as follows, viz.

Staff productivity = Total value of work done/ No. of man months deployed= 8, 00,302 Man months

P&M productivity

Budgeted turn over to depreciation ratio = Budgeted Turn over in Rs. Lakhs/ Depreciation in Rs. lakhs = 17.50

Actual turn over to depreciation ratio = Actual Turn over in Rs .Lakhs/ Depreciation in Rs.lakhs= 21.31

Labour productivity (Average)

Shuttering = 2.8 Sqm/Man days

Reinforcement = 0.15 MT/Man days

Concrete = 5.55 cum/Man days

Quality Control and Quality Assurance

Well equipped laboratory set up, was provided and managed by qualified experienced professionals. All tests were carried out as per the site quality plan and the test results were recorded and documented as per ISO 9001 Clause no. (4.2.2- Quality Manual, 4.2.3- Control of Documents, 4.2.4- Control of Records).To handover the project without non-conformance, all the process was controlled by implementation of ITP (Instruction & Testing Procedure).

Information compilation by:

1. Rajiv Mahajan, COO (North)
2. P.V.Prasanth, COO (South)
3. C.A.Prasad, Asst.Vice President