NUMERICAL ANALYSIS OF REINFORCED CONCRETE SPHERICAL DOME SHELL AND CYLINDRICAL SHELL STRUCTURES UNDER DIFFERENT APPLIED LOADS.

Abstract

Shell structures are mostly thin walled curved surface structures in which the thickness is rather small compared to the lateral dimensions and radii of curvature. Shells constitute among the most common and most efficient structural elements in nature and technology, they are used whenever high strength, large spans and minimum materials are required. Shells' geometrical properties are the most fundamental characteristics that distinguish their internal force system from that of other types of structural forms plated structures. Because of their geometrical form that efficiently support applied external forces, shell structures are available in a variety of shapes and sizes, including spherical, cylindrical, conical, and translational shapes and sizes. The buckling of shells under specific static or dynamic loading circumstances is a particular mode of shell instability. As a result, the stability analysis of thin shells becomes crucial in a number of issues involving the design of shells. A spherical shell is synclastic, non-developable, doubly curved surface. As a result, the critical stability load of a spherical shell is typically higher than a concrete shells with a single curvature. One of the key design considerations for such a shell is the possibility of buckling. For rise to radius ratio up to 0.716 and 0.74 the edge moment and edge shear acted on the ring beam are outward to the dome respectively. For rise to radius ratio after to 0.716 and 0.74 the edge moment and edge shear acted on the ring beam are towards the dome respectively. The range of xaxis crossing points of rise to radius ratio are the minimum bending forces ranges. For rise to radius ratio value less than 0.5 the wind load acted on the dome is suction type as a result the internal membrane meridional and hoop forces are tensile type while for greater or equal to 0.50, the wind pressure acted towards the dome, thus the internal membrane meridional and hoop forces are compressive type. For wind load the minimum membrane forces are in the range of 0.50 to 0.70. From a structural buckling assessment of analyzed concrete shells it can be concluded that shells can be extremely sensitive with respect to slight deviation of their ideal parameters like initial geometry and boundary conditio