Mallareddy Hospital, located in Suraram in northern Hyderabad, is a well-known healthcare facility. The architectural design concepts for the hospital were provided by architect Praveen from TRU Designs, a Hyderabad-based architectural firm.
The auditorium building comprises a cellar floor, a ground floor, a first floor, and a second floor. The auditorium itself begins at the first-floor level (4.0 m) and extends up to 12 m, featuring a sloping slab inside. The dome installation starts at a height of 15.6 m from the ground.
Designed in a circular layout, the auditorium has a seating capacity of 1,250 people. The roof features a steel dome structure with an outer diameter of 41m and a height of 12.5 m. The dome is supported by 16 evenly spaced spokes, positioned at 22.5° intervals. Each spoke is a triangular lattice structure, forming an equilateral triangle with 1,200 mm sides.
V Sridhar Reddy, Managing Director of Sri Harsha Consulting Engineers Pvt Ltd, provides deeper insights into the key aspects of the project, highlighting the structural challenges, innovative solutions, and the rationale behind crucial design decisions.
Design Philosophy
Initially, the architect envisioned the dome as an RCC structure. However, given the dome’s large diameter, constructing it in RCC would require extensive scaffolding and highly precise workmanship to achieve the desired shape.
The auditorium’s bottom slab is designed with a slope to enhance seating arrangements and provide a better visual connection to the stage. However, setting up scaffolding on this sloped surface, with varying heights, poses a significant challenge. This approach would also be time-consuming and might not guarantee the exact dome shape as intended in the architectural design.
Additionally, constructing a 41 m diameter dome in RCC is not a practical solution, as it would require a slab thickness of 250-300 mm, adding unnecessary dead load to the structure. Overall, an RCC dome for such a large span is not economically viable compared to a steel structure.
Considering these challenges, the idea of a steel dome structure was proposed to the architect, who readily accepted it. The dome was designed using triangular lattice configurations to enhance bending capacity in both directions. Given the high-altitude erection requirements, the triangular shape was chosen for its superior stability compared to a flat lattice structure during installation.
The Material Specification
The dome structure is entirely composed of Square Hollow Section (SHS) members, all sourced from Apollo Tubes. The primary chords of the triangular lattice are SHS 113.5 x 113.5 x 4.8 mm, internally connected by SHS 80 x 80 x 4 mm members. The spokes of the dome are connected using SHS 113.5 x 113.5 x 5.4 mm up to a height of 7.2 m from the base, while the remaining sections utilise SHS 100 x 100 x 4 mm members.
At the centre of the dome, a structural ring with a diameter of 7 m has been designed using an I-section fabricated from a 12 mm thick plate. This central ring is connected to the 16 spokes using SHS 113.5 x 113.5 x 4.8 mm members, providing stability and load distribution. To facilitate the secure connection of the spokes, pre-drilled holes have been incorporated into the central ring, allowing for bolted assembly.
At the slab level, each spoke is anchored using 24 high-strength bolts of 20 mm diameter, ensuring a stable and durable connection between the dome and the supporting structure.
Erection Process
The erection of this dome structure was highly complex due to the convergence of all 16 lattice spokes at the center. To facilitate a proper load path and ensure structural stability, a 7 m diameter central ring was introduced, allowing all 16 lattices to connect seamlessly.
The sequence of erection was crucial to maintaining stability. The method followed involved erecting the first spoke on the northern side, followed by the second on the southern side, then the third on the eastern side, and the fourth on the western side. This alternating approach, installing one spoke in one direction and the next in the opposite direction, ensured balanced structural support during the process.
The erection began with lifting the central ring into position using a 500 tonne capacity crane with a large boom capable of handling a tip load of 10 tonne. The central ring was held in place until all the spokes were attached.
For lifting the spokes, a 250 tonne capacity crane was used to hoist each spoke to the required height, securing them at both the slab level and the central ring level. This process was repeated for all 16 spokes until the entire framework was in place. Once the spokes were installed, lateral ties were fixed at 1.2 m intervals to enhance stability.
After completing the structural framework, a 1.2 mm plain galvanised sheet was installed across the entire dome surface. A weld mesh was then affixed to this sheet, followed by reinforcement placement. Shotcreting was carried out with a 75 mm thickness to create a durable surface, and waterproofing was applied as the final protective layer.
Upon completion, the architect envisioned painting half of the planet Earth on the dome’s surface, adding an artistic and symbolic element to the structure.
Fact File
Project: Mallareddy Hospital Auditorium, Hyderabad
Client: Malla Reddy
Architect: Tru Designs
Structural Consultant: Sri Harsha Consulting Engineers Pvt Ltd
Fabricator: SS Industries
Supplier: Apollo Tubes
Tonnage: 105 tonne
Status: Ongoing
Expected Completion Year: 2025
