The Auditorium building is located on the hillock area and the roof profile is matching the geological profile surroundings of the site. The proposed steel structure is spread over an area of about 3139 sq. m. The building consists of ground floor covered with structural steel space frame members. The roofing system is curved and covered with galvalume sheeting and has insulation for thermal gradient. This entire roofing system rests on RCC column/footings.
The steel girders are spaced over the RCC columns at a varying interval from 4.5m to 6.0m on the periphery. The main girder cross section is triangular in shape varying from 750 x 1800mm at center to 750 x 900mm at ends, spanning 28m between columns. The triangular girder continues along the same slope and is anchored to the ground on a pedestal. The entire structural analysis of the 3D space frame has been carried out using STAAD Pro software. The structural members of the girders, purlins, and bracings are all tubular sections of YST 310 grade (CHS/RHS/SHS).
The large span, roof profile, construction timing and overall economy determine the necessity to adopt and propose structural steel system and roofing. There is also added advantage for addition and alteration space for future requirements considering its flexibility of the material. Hence the specific space frame and tubular configuration.
Efficiency in Fabrication
The hollow sections by inherent nature are stable for torsion and by formulation of triangular cross section of the girder and the curved nature of the roof profile, makes it extremely rigid for strength, stability or serviceability. The structural design, by virtue of material (RHS/SHS/CHS) coupled with geometry and shape of the roofing system is extremely economical. The structural steel consist of NB Pipes/SHS/RHS sections used are to the tune of 96 MT for an area of 34500 sq. ft. in plan. The galvalume sheet roofing laid for an area of 3200 sq. m is fixed with self-tapping screws. The sheet profile has been adequately achieved to the architectural requirement
The choice of the material for roofing was steel due the span and curved profile. The entire fabrication can be done on-site. The bending of the tubular section to the required shape was a challenge that was adequately met at the site. The profiling is derived with help of a hydraulic bending machine. The structural steel system was required in the curved profile, hence there was no choice other than using hollow section and is the right choice. Full penetration butt welding or fillet welding were done as per the design requirement. The space truss were made into two halves and erected with the help of a heavy-duty crane. These halves were joined together with full welding all-round. The truss, it displayed excellent stability during erection, thanks to its three dimensional design.
During inspection, the contractor derived shop marking, and the same got approved in record time. Precision was a pre-requisite on account of the girders bearing a curved profile. The fabrication and erection of the roofing system was required to be precise both due to three dimensional nature and curved form. The erection of the entire roofing was done with the help of a crane, thereby achieving proper alignment of girders and purlins.
The space frame remains visible for stipulated scheduled visual inspection as a part of routine facility management compulsions and can be treated and maintained by applying appropriate system without the necessity of erecting scaffolding from the floor. Simple employment of gondolas etc. permit the quick maintenance and upkeep of the structural system. A schedule towards assessment of corrosion and weathering impact can also be aligned towards the upkeep of the facility
The structural system is configured and engineered as per good engineering practice as stipulated in required codal provision. Appropriate QA – QC measures were deployed during the stages of fabrication, erection, inspection and commissioning of the system in line with the defined design basis.