Saurashtra University, Rajkot, has developed a party plot for community centre at the university campus. In this, a stage of 11.0 m x 20.0 m with two rooms on either side of the stage, with size 7.0 m x 5.0 m each, was proposed as part of the overall plot development.
As an attempt to impart a unique character to the proposed structure, a system comprising of three large span (47 m) concrete arches was conceived.
Structural system comprises of three concrete arches at 5.5 m c/c. The arch starts from ground itself at both ends. Span of arch between supports at foundation level is 47.2 m and that at ground level is 40.47 m. Central rise above ground is 5.95 m. Arch section is 0.45 m x 0.75 m.
Slab with secondary beams has been provided to cover the stage as well as the rooms. But the main system supporting the whole structure is composed of three large span arches which covers almost 50 m x 11 m column free area. Arch being a compressive element; full utilization of compressive strength of concrete has been achieved.
The system of a series of three arches posed a problem while resisting the earthquake forces perpendicular to the plane of arches. To resist these forces, four shear walls were required to be provided. North-south walls of both side rooms were made concrete shear walls.
Second problem was to develop an effective system to resist horizontal thrust transferred by the arch at its support. As foundation with good quality rock was available on site, rock anchors in shear were used to provide horizontal reaction of the foundation.