COVER STORY

COMMERCIAL BUILDING KHARGHAR

COMMERCIAL-BUILDING

Design Concept
The site is located in the north-east corner of a residential complex in Kharghar, Navi Mumbai. The elongated southern section of the site is reserved for a future low-rise residential development, and the commercial building is restricted to the elongated L-shaped bulb at the northern extremity.

The raised residential development on the west, resulting in a sunken section within the site, along with the shape of the plot, the orientation of the views, and the surrounding hills stretching from west to east along the north, and the fragmented building program have contributed to the development of the building concept.

Two perpendicularly oriented prisms form the bulk of the building area. The lower one contains flexible, free span work spaces for sale/lease, and the upper one is specifically formatted to suit the requirements of the client’s corporate office. The long and slender lower block hovers above a landscaped sunken courtyard that also contains the lobby and public spaces. The building volume serves as a transition point between two conditions within the landscape. On the south, where cars approach the lobby, the building projects out from a steeply banked grass berm that merges the levels from the road access to the raised section on the west. The movement under this hovering monolith creates a volumetric expansion towards the north where a large water sheet creates a space of calm and reflection where the lobby and public areas open out onto.

This movement is a spatial and transitional analog for the barely plausible relationship between the upper and lower building blocks. The impression is one of balancing on the edge as the upper block turns at 90 degrees and perches delicately on the lower one, cantilevering out 16.0m over the sunken courtyard below.

This volumetric separation and reorientation reduces the perceived mass of the building, creating inverted and differentially scaled ‘T’ sections in 2 axes, and especially as the building is approached, the sensation is of an elongated edge hovering above the water and a large prism balancing delicately over it. From a distance, the volume of the corporate office becomes the attractor, a point of reference.

Structurally Fluent
These precise transitions need a highly tuned and nuanced set of structural solutions, as well as a unified skin that would break from the traditional scale of a stratified expression, developing instead a more ambiguous monolithic proportion that would heighten the sense of a series of precarious intersections between massive, porous volumes.

Apart from the shear core in the south, the superstructure consists primarily of steel. A lightweight web of slender members expresses the structural behavior of the building. The final solution is simple and elegant, but disguised within this coherent network is a complex engineering process that has effectively managed to reconcile an ambitious idea with the practical optimization and scalable replication and detailing during the fabrication process that is required to execute the structure.

The structural configuration went through multiple iterations before the design team reached a solution, but overall, it was found that the engineers from Cantor Seinuk (WSP) were able to substantially reduce the material consumption and member sizes by working with a delicate, distributed web. The maximum impact has been achieved at the ground level and volumetric intersection points where a lightness that is commensurate with the design intent has been expressed.

Aesthetics and Exteriors
The double skin solution, with superimposed layers of glass and a punched/perforated aluminum screening system enables excellent views outside of the office spaces while filtering the glare and heat. Controlled daylight floods the internal spaces, reducing energy costs through a scientific analysis of perforation patterns while also eliminating the need for any internal solar control blinds.

This layered assembly of perforated aluminum, glass and the exposed network of structural members creates a sense of density, lightness and porosity that vitiates the mass of the building volumes.

FAST FACTS

ARCHITECT
Malik Architecture

STRUCTURAL CONSULTANT
Cantor Seinuk (WSP)

SOFTWARE USED
STAAD Pro, Acad, Revit, TEKLA

STEEL SECTIONS
ISMB, ISLC, ISMC, RHS, SHS, UB

STEEL GRADES
Fe 410 (YST-250 Mpa)/ Fe 490 B (YST-350 Mpa)

STEEL TONNAGE
1200 MT

CURRENT STATUS
Tender Stage

The Warehouse Park Phase1, Hyderabad

Zeromile Warehousing Pvt. Ltd, a reputed name in the country in warehousing and logistics, approached the Consultant, Epicenter Consulting Engineers Pvt. Ltd., with their intention to develop a 36-acre land near Hyderabad (T.S) into a Warehouse Park. They wanted it to contain 4 giant warehouses, with a cumulative area of around one million square feet, and to be developed in different phases. The plan dimensions of the warehouses were decided by ZMW based on logistics and local regulations among other factors. Consultant was informed that the sub-soil strata consisted of shallow sheet rock for majority of the plot area, and that it was hard soil for remaining area.

Ideation
As the 2 warehouses in ‘Phase-1’ were to be leased to MNCs that focused on e-commerce, cloud computing, digital streaming and artificial intelligence, Sundeep Reddy – ZMW Director wanted the warehouses and related infrastructure to be designed as per International Standards.

Before the Consultants took on the structural design, they had to work on, and freeze, some important design parameters such as warehouse height, roof slope, column spacing, fire protection methods, solar panel requirements, lighting, ventilation etc. The sub-soil exploration was considered as 10m deep boreholes, and 3m deep trial pits, scattered evenly over the site extent.

Steel Significance
In view of the requirements for larger eaves height and greater column spacing, the “steel” gable frame emerged as the clear winner when compared with RCC frame or even composite construction with trusses. It was entirely structural steel from above the warehouse plinth. RCC was confined to sub-structure, while a 5′ high block-wall enclosed each warehouse.

Sayed Hyder Hussaini

With spans of 110m and 100m for the double gable frame, restricting lateral sway, longitudinal drift and member deflections within allowable limits was a challenge. Another challenge was to limit the steel tonnage to the least we could. With gigantic dimensions, this was not easy. After several design options regarding the support conditions, frame spacing, braced bay locations, member profiles and member releases, we could achieve a gross tonnage well below 5 kg/sq. ft. Our tactical blend of ‘fixed’ and ‘pinned’ supports brought down the overall warehouse cost by approximately 20 per cent from the initial estimate. A customized automated template was especially developed to obtain design wind pressures for various structural elements of the space frame. Likewise, baseplates, anchor bolts, stiffeners and shear keys were all designed using ‘in-house’ ECE software.

Sayed Hyder Hussaini
Managing Director,
Epicenter Consulting Engineers Pvt Ltd

Features
Sundeep Reddy, with his rich experience gained over the years, has been actively involved in the architectural and logistic aspect of the project from the beginning. He made the Architects to work on a variety of options with regards to elevations, fascia, entrance, skylights, mezzanine layouts, canopies, docking and parking facilities from which the final ideas were selected and forwarded to ECE for the next phase viz. Structural Design, Tekla Modeling and Connection Design.

Geometrics
Warehouse in Phase-1 consists of a double-gable space frame with an area of 4,26,000 sq. ft., and had started initially as two independent units, 100mx177m each, spaced 10m apart. Subsequently, the units were merged into a double-gable unit as required by end user. It has already been taken by Mahindra Logistics, who as a 3 PL service provider will house Amazon as the customer.

Six rows of 16m span jack-beams run along the building length supporting rafters for alternate frames. Sheeting consists of seamless profiles from reputed Indian suppliers.

Both the side walls have 5m wide continuous canopies running along the building length in reverse slope. The warehouse has 26,500 sq. ft. of mezzanines, continuous roof monitors, firefighting system, sky lighting, ventilators & dock levelers in addition to an elegant fascia on its front.

Foundation consists of 200 footings, with an equal number of concentric pedestals, resisting wind shear and bending moments, in addition to the usual gravity loads. A 300mm thick RCC wall ties the edge pedestals, thus restricting their bending about their major axes, while retaining the 1.2m deep soil from within the building.

Learnings
One of the challenges for Consultant was to limit steel tonnage to the least possible. With 13.5m eaves height and huge column free area requirements, this was not easy. The Consultants, therefore, worked with several permutations and combinations, varying support conditions, frame spacing, member profiles and even member releases, to finally arrive at the most economical structural configuration. Member profiles were based on moment envelopes, connections were both ‘shear’ and ‘moment’ type and adequate splices were introduced considering transportation limitations.

Restricting lateral sway, structure drift and rafter deflections to within limits was another big challenge. Structural design was done as per AISC–ASD, while serviceability criteria were based on MBMA-2006

Another design challenge was the fact that the ‘double-gable’ warehouse was to be built as two separate warehouses at different points of time, such that the functioning of the first unit would not have to be interrupted while the second unit was being built. This, therefore, required the structure to be prudently analyzed for below two scenarios:

  • As two single units, 100m x 177m each (spaced 10m apart).
  • As one single unit, 210m x 177m.

Member sizes governed by the above two cases were considered as the required sizes. Though steel tonnage increased slightly, this was necessary to account for effects of a possible ‘strong wind’ on the first unit until construction of the balance part viz. second unit.

To ensure uninterrupted operation of the first unit, steel brackets were designed and fixed to each column along common line. These would later support rafters of the second unit. Special precautions were taken for design of valley gutter, associated RWPs and internal drains in view of the huge contributory area from adjacent roofs.

Usually, economical configurations require extreme columns to be ‘fixed’, internal columns to be ‘pinned’ and columns for cantilevers to be ‘prismatic’.

Exceptionally high soil SBCs (200 ton/sq. m in present case) help reduce footing and pedestal sizes, even for fixed supports. Fixed column supports result in heavier footings and pedestals (60 per cent heavier in present case), but it brings down the overall warehouse cost by at least 20 per cent.

Though the total duration of Phase-1 including design, construction, fabrication, erection and flooring was initially estimated at 10 months, it is likely to exceed the schedule by at least 50 per cent because of Covid-19 pandemic.

Software Details
Structural Analysis & Design: STAAD.Pro
Drafting: AutoCAD/ ZWCAD
Detailing/ Modeling: Tekla Structures
Footing & Pedestal Design: ECE Software
Wind Loads: ECE Template
Connection Design: RAM Connection/ ECE Software
Detailed Steel MTO : ECE Template

Fact File
Client, Developer& PMC: Zeromile Warehousing Pvt. Ltd
Structural Consultant: Epicenter Consulting Engineers Pvt. Ltd
Steel Supplier & Fabricator: Kirby Building Systems
& Structures India Pvt Ltd
Architects: F6 Architects
Steel Tonnage: 2000 MT
Status: Ongoing

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