National Aviation University, Department of Computer Technology of Construction

The paper deals with the behavior of cylindrical steel capacity under the load with different number of vertical stiffeners. It was studied both short constructions with the clamp in all points and relatively tall constructions with the clamp in only supporting points of ribs. Quantities of radial deflections was compared for capacities made from flat and shaped sheets of different thickness. It was shown that deflections of capacities will be bigger than capacities without ribs under axially symmetric load and small quantity of ribs. During the increase of the quantity of ribs, bending deflections is expanding too until they obtain their maximum point. After this monotone decrease began. The given tendency is the general characteristic feature of capacities of both flat and shaped sheets. But it differs in place of deflection points in quantitative ratio. Under the asymmetric load and small quantity of vertical ribs the quantity of deflections is far less than in ribless capacities. A domain can appear for shells from flat sheets of small thickness within which deflections increase insignificantly. The shape, length, main geometric characteristics of vertical ribs and their influence on the work of the capacity were studied in details. It was represented approximate formulas that allow estimating correctly the area of cross-section, moment of inertia and moment of the rib support in wide range of thicknesses value. The given numerical example illustrates convenience of doing preliminary estimate of the rib thickness in safety margin. It was analyzed the changing of longitudinal force and bending moment in vertical ribs and their strain in capacity under axially symmetric expanding effort and under the asymmetric load, according to diagram of wind pressure. The results show that end effect for capacities of small elongation spread to all the height under axially symmetric expanding effort. But it decays in some way near the middle of the capacity, which thickness is growing. The higher is the capacity, the lesser is the effect of ribs on its stiffness. And zone of the end effect moves to the end wall. During the
increase of the thickness of capacity, the diagram of moments is buckling and a domain for zero value moments is appearing. Under the asymmetric load the efficiency of vertical ribs increases, particularly when its number is big enough. It was mentioned graphical illustrations of capacities’ deflection in different combinations of loads and variation of rib’s height, pattern and the thickness of sheets of the body.

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