Nonlinear analysis of carrying capacity of reinforced concrete smooth and ribbed shells under action of concentrated load

Reinforced concrete shells for industrial and civil buildings roofings should carry considerable value of concentrated loads of suspended transport, technological equipment, suspended ceiling and so on. In this paper engineering methods to solve the problems of analysis of bearing capacity dealing with deformed state of reinforced concrete smooth and ribbed shallow shells of positive Gaussian curvature under action of concentrated load are considered. The solution of problems is executed on the basis of a kinematic method of limit equilibrium [1] in nonlinear statement with some possible schemes of failure found experimentally [2]. Round in the plan reinforced concrete shallow shells of positive curvature under the action of the concentrated load applied in the top, fail with formation of complete radial or local failure schemes. In the complete scheme of destruction radial cracks locate at full height of the shell, including a basic ring in which the reinforcement amounts to ultimate tensile strength. Experimental investigation carried out on models and full scale structures have shown that the local failure schemes peculiar to more thin and shallow shells. For this shells the outline in the plan was of no importance if the zone of failure not border upon the contour. The zone of failure is surrounded with the ring crack formed in result of eccentric compression of sections, perpendicular to radial ones. In ring direction near to edge of a failure zone in ultimate state the reinforcement of the shell amounts to ultimate tensile strength. Bearing capacity of ribbed shells considerably grows in comparison with smooth shells. The concentrated load, as a rule, is applied in the places of crossing of longitudinal and transversal ribs of a shell (Fig. 1).

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